Modeling
Simulation
Implementation
Model-Based and System-Based Design
?
Writing S-Functions
Version 5
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Writing S-Functions
? COPYRIGHT 1998 - 2002 by The MathWorks, Inc.
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Printing History: October 1998 First printing Revised for Simulink 3.0 (Release 11)
November 2000 Second printing Revised for Simulink 4.0 (Release 12)
June 2001 Online only Revised for Simulink 4.1 (Release 12.1)
July 2002 Online only Revised for Simulink 5.0 (Release 13)
Contents
1
Overview of S-Functions
What Is an S-Function? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
Using S-Functions in Models . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Passing Parameters to S-Functions . . . . . . . . . . . . . . . . . . . . . . 1-4
When to Use an S-Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
How S-Functions Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Mathematics of Simulink Blocks . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Simulation Stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
S-Function Callback Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
Implementing S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
M-File S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
MEX-File S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
S-Function Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
Direct Feedthrough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
Dynamically Sized Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
Setting Sample Times and Offsets . . . . . . . . . . . . . . . . . . . . . . 1-15
S-Function Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18
2
Writing M S-Functions
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
S-Function Arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
S-Function Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Defining S-Function Block Characteristics . . . . . . . . . . . . . . 2-5
i
ii Contents
Processing S-Function Parameters . . . . . . . . . . . . . . . . . . . . . 2-6
Examples of M-File S-Functions . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Simple M-File S-Function Example . . . . . . . . . . . . . . . . . . . . . . 2-7
Example - Continuous State S-Function . . . . . . . . . . . . . . . . . . 2-9
Example - Discrete State S-Function . . . . . . . . . . . . . . . . . . . . 2-12
Example - Hybrid System S-Function . . . . . . . . . . . . . . . . . . . 2-14
Example - Variable Sample Time S-Function . . . . . . . . . . . . . 2-17
3
Writing S-Functions in C
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Creating C MEX S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Building S-Functions Automatically . . . . . . . . . . . . . . . . . . . . 3-5
S-Function Builder Dialog Box . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
Setting the Include Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23
Example of a Basic C MEX S-Function . . . . . . . . . . . . . . . . . 3-25
Defines and Includes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-27
Callback Implementations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-27
Simulink/Real-Time Workshop Interface . . . . . . . . . . . . . . . . . 3-29
Building the Timestwo Example . . . . . . . . . . . . . . . . . . . . . . . . 3-30
Templates for C S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . 3-31
S-Function Source File Requirements . . . . . . . . . . . . . . . . . . . 3-31
The SimStruct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33
Compiling C S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-34
How Simulink Interacts with C S-Functions . . . . . . . . . . . . 3-35
Process View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-35
Data View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39
Writing Callback Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-43
Converting Level 1 C MEX S-Functions to Level 2 . . . . . . . 3-44
Obsolete Macros . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-46
4
Creating C++ S-Functions
Source File Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Making C++ Objects Persistent . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
Building C++ S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
5
Creating Ada S-Functions
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
Ada S-Function Source File Format . . . . . . . . . . . . . . . . . . . . . 5-3
Ada S-Function Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
Ada S-Function Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
Writing Callback Methods in Ada . . . . . . . . . . . . . . . . . . . . . . . 5-6
Callbacks Invoked by Simulink . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
Implementing Callbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Omitting Optional Callback Methods . . . . . . . . . . . . . . . . . . . . . 5-7
SimStruct Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Building an Ada S-Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
Ada Compiler Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
Example of an Ada S-Function . . . . . . . . . . . . . . . . . . . . . . . . 5-10
iii
iv Contents
Creating Fortran S-Functions
6
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
Level 1 Versus Level 2 S-Functions . . . . . . . . . . . . . . . . . . . . . . 6-2
Creating Level 1 Fortran S-Functions . . . . . . . . . . . . . . . . . . . 6-3
The Fortran MEX Template File . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Inline Code Generation Example . . . . . . . . . . . . . . . . . . . . . . . . 6-6
Creating Level 2 Fortran S-Functions . . . . . . . . . . . . . . . . . . . 6-7
Template File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
C/Fortran Interfacing Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
Constructing the Gateway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11
Example C-MEX S-Function Calling Fortran Code . . . . . . . . . 6-13
Porting Legacy Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
Find the States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
Sample Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
Multiple Instances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
Use Flints If Needed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-15
Considerations for Real Time . . . . . . . . . . . . . . . . . . . . . . . . . . 6-15
7
Implementing Block Features
Dialog Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2
Tunable Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3
Run-Time Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5
Creating Run-Time Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 7-6
Updating Run-Time Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
Creating Input and Output Ports . . . . . . . . . . . . . . . . . . . . . . . 7-8
Creating Input Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8
Creating Output Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10
Scalar Expansion of Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11
Masked Multiport S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . 7-12
Custom Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14
Sample Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-15
Block-Based Sample Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16
Specifying Port-Based Sample Times . . . . . . . . . . . . . . . . . . . . 7-18
Hybrid Block-Based and Port-Based Sample Times . . . . . . . . 7-22
Multirate S-Function Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-23
Synchronizing Multirate S-Function Blocks . . . . . . . . . . . . . . 7-24
Work Vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-26
Work Vectors and Zero Crossings . . . . . . . . . . . . . . . . . . . . . . . 7-28
Example Involving a Pointer Work Vector . . . . . . . . . . . . . . . . 7-28
Memory Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-30
Function-Call Subsystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31
Handling Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-33
Exception Free Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-33
ssSetErrorStatus Termination Criteria . . . . . . . . . . . . . . . . . . 7-34
Checking Array Bounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-35
S-Function Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-36
Example of a Continuous State S-Function . . . . . . . . . . . . . . . 7-36
Example of a Discrete State S-Function . . . . . . . . . . . . . . . . . . 7-41
Example of a Hybrid System S-Function . . . . . . . . . . . . . . . . . 7-45
Example of a Variable-Step S-Function . . . . . . . . . . . . . . . . . . 7-49
Example of a Zero Crossing S-Function . . . . . . . . . . . . . . . . . . 7-52
Example of a Time-Varying Continuous Transfer Function . . 7-64
8
Writing S-Functions for Real-Time Workshop
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2
Classes of Problems Solved by S-Functions . . . . . . . . . . . . . . . . 8-2
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vi Contents
Types of S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3
Basic Files Required for Implementation . . . . . . . . . . . . . . . . . . 8-5
Noninlined S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7
S-Function Module Names for Real-Time Workshop Builds . . . 8-7
Writing Wrapper S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9
MEX S-Function Wrapper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9
TLC S-Function Wrapper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14
The Inlined Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-18
Fully Inlined S-Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-19
Multiport S-Function Example . . . . . . . . . . . . . . . . . . . . . . . . . 8-19
Fully Inlined S-Function with the mdlRTW Routine . . . . . 8-21
S-Function RTWdata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-22
The Direct-Index Lookup Table Algorithm . . . . . . . . . . . . . . . . 8-23
The Direct-Index Lookup Table Example . . . . . . . . . . . . . . . . . 8-24
Creating Code-Reuse-Compatible S-Functions . . . . . . . . . . 8-42
9
S-Function Callback Methods
mdlCheckParameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2
mdlDerivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4
mdlGetTimeOfNextVarHit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-5
mdlInitializeConditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6
mdlInitializeSampleTimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-8
mdlInitializeSizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12
mdlOutputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16
mdlProcessParameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-17
mdlRTW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-19
mdlSetDefaultPortComplexSignals . . . . . . . . . . . . . . . . . . . . . 9-20
mdlSetDefaultPortDataTypes . . . . . . . . . . . . . . . . . . . . . . . . . . 9-21
mdlSetDefaultPortDimensionInfo . . . . . . . . . . . . . . . . . . . . . . 9-22
mdlSetInputPortComplexSignal . . . . . . . . . . . . . . . . . . . . . . . . 9-23
mdlSetInputPortDataType . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-24
mdlSetInputPortDimensionInfo . . . . . . . . . . . . . . . . . . . . . . . . 9-25
mdlSetInputPortFrameData . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-27
mdlSetInputPortSampleTime . . . . . . . . . . . . . . . . . . . . . . . . . . 9-28
mdlSetInputPortWidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-30
mdlSetOutputPortComplexSignal . . . . . . . . . . . . . . . . . . . . . . 9-31
mdlSetOutputPortDataType . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-32
mdlSetOutputPortDimensionInfo . . . . . . . . . . . . . . . . . . . . . . . 9-33
mdlSetOutputPortSampleTime . . . . . . . . . . . . . . . . . . . . . . . . . 9-35
mdlSetOutputPortWidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-36
mdlSetWorkWidths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-37
mdlStart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-38
mdlTerminate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-39
mdlUpdate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-40
mdlZeroCrossings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-41
10
SimStruct Functions
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2
Language Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2
The SimStruct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2
SimStruct Macros and Functions Listed by Usage . . . . . . . 10-3
Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3
Error Handling and Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3
I/O Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4
Dialog Box Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-9
Run-Time Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10
Sample Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-11
State and Work Vector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13
Simulation Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-17
Function Call . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-19
Data Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-19
Real-Time Workshop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-20
Macro Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-22
ssCallExternalModeFcn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-23
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viii Contents
ssCallSystemWithTid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-24
ssGetAbsTol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-25
ssGetBlockReduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-26
ssGetContStateAddress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-27
ssGetContStates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-28
ssGetDataTypeId . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-29
ssGetDataTypeName . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-30
ssGetDataTypeSize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-31
ssGetDataTypeZero . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-32
ssGetDiscStates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-33
ssGetDTypeIdFromMxArray . . . . . . . . . . . . . . . . . . . . . . . . . . 10-34
ssGetDWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-36
ssGetDWorkComplexSignal . . . . . . . . . . . . . . . . . . . . . . . . . . 10-37
ssGetDWorkDataType . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-38
ssGetDWorkName . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-39
ssGetDWorkRTWIdentifier . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-40
ssGetDWorkRTWStorageClass . . . . . . . . . . . . . . . . . . . . . . . . 10-41
ssGetDWorkRTWTypeQualifier . . . . . . . . . . . . . . . . . . . . . . . 10-42
ssGetDWorkUsedAsDState . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-43
ssGetDWorkWidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-44
ssGetdX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-45
ssGetErrorStatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-46
ssGetInlineParameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-47
ssGetInputPortBufferDstPort . . . . . . . . . . . . . . . . . . . . . . . . . 10-48
ssGetInputPortComplexSignal . . . . . . . . . . . . . . . . . . . . . . . . 10-49
ssGetInputPortConnected . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-50
ssGetInputPortDataType . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-51
ssGetInputPortDimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-52
ssGetInputPortDirectFeedThrough . . . . . . . . . . . . . . . . . . . . 10-53
ssGetInputPortFrameData . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-54
ssGetInputPortNumDimensions . . . . . . . . . . . . . . . . . . . . . . . 10-55
ssGetInputPortOffsetTime . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-56
ssGetInputPortOverWritable . . . . . . . . . . . . . . . . . . . . . . . . . 10-57
ssGetInputPortRealSignal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-58
ssGetInputPortRealSignalPtrs . . . . . . . . . . . . . . . . . . . . . . . . 10-60
ssGetInputPortRequiredContiguous . . . . . . . . . . . . . . . . . . . . 10-61
ssGetInputPortReusable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-62
ssGetInputPortSampleTime . . . . . . . . . . . . . . . . . . . . . . . . . . 10-63
ssGetInputPortSampleTimeIndex . . . . . . . . . . . . . . . . . . . . . 10-64
ssGetInputPortSignal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-65
ssGetInputPortSignalAddress . . . . . . . . . . . . . . . . . . . . . . . . . 10-66
ssGetInputPortSignalPtrs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-67
ssGetInputPortWidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-68
ssGetIWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-69
ssGetIWorkValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-70
ssGetModelName . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-71
ssGetModeVector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-72
ssGetModeVectorValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-73
ssGetNonsampledZCs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-74
ssGetNumContStates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-75
ssGetNumDataTypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-76
ssGetNumDiscStates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-77
ssGetNumDWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-78
ssGetNumInputPorts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-79
ssGetNumIWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-80
ssGetNumModes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-81
ssGetNumNonsampledZCs . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-82
ssGetNumOutputPorts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-83
ssGetNumParameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-84
ssGetNumRunTimeParams . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-85
ssGetNumPWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-86
ssGetNumRWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-87
ssGetNumSampleTimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-88
ssGetNumSFcnParams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-89
ssGetOutputPortBeingMerged . . . . . . . . . . . . . . . . . . . . . . . . 10-90
ssGetOutputPortComplexSignal . . . . . . . . . . . . . . . . . . . . . . . 10-91
ssGetOutputPortDataType . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-92
ssGetOutputPortDimensions . . . . . . . . . . . . . . . . . . . . . . . . . 10-93
ssGetOutputPortFrameData . . . . . . . . . . . . . . . . . . . . . . . . . . 10-94
ssGetOutputPortNumDimensions . . . . . . . . . . . . . . . . . . . . . 10-95
ssGetOutputPortOffsetTime . . . . . . . . . . . . . . . . . . . . . . . . . . 10-96
ssGetOutputPortRealSignal . . . . . . . . . . . . . . . . . . . . . . . . . . 10-97
ssGetOutputPortReusable . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-98
ssGetOutputPortSampleTime . . . . . . . . . . . . . . . . . . . . . . . . . 10-99
ssGetOutputPortSignal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-100
ssGetOutputPortSignalAddress . . . . . . . . . . . . . . . . . . . . . . 10-101
ssGetOutputPortWidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-102
ssGetParentSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-103
ssGetPath . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-104
ssGetPlacementGroup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-105
ix
x Contents
ssGetPortBasedSampleTimeBlockIsTriggered . . . . . . . . . . 10-106
ssGetPWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-107
ssGetPWorkValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-108
ssGetRealDiscStates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-109
ssGetRootSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-110
ssGetRunTimeParamInfo . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-111
ssGetRWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-112
ssGetRWorkValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-113
ssGetSampleTimeOffset . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-114
ssGetSampleTimePeriod . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-115
ssGetSFcnParam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-116
ssGetSFcnParamsCount . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-117
ssGetSimMode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-118
ssGetSolverMode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-119
ssGetSolverName . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-120
ssGetStateAbsTol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-121
ssGetStopRequested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-122
ssGetT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-123
ssGetTaskTime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-124
ssGetTFinal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-125
ssGetTNext . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-126
ssGetTStart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-127
ssGetUserData . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-128
ssIsContinuousTask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-129
ssIsFirstInitCond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-130
ssIsMajorTimeStep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-131
ssIsMinorTimeStep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-132
ssIsSampleHit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-133
ssIsSpecialSampleHit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-134
ssIsVariableStepSolver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-135
ssPrintf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-136
ssRegDlgParamAsRunTimeParam . . . . . . . . . . . . . . . . . . . . 10-137
ssRegAllTunableParamsAsRunTimeParams . . . . . . . . . . . . 10-138
ssRegisterDataType . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-139
ssSampleAndOffsetAreTriggered . . . . . . . . . . . . . . . . . . . . . 10-140
ssSetBlockReduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-141
ssSetCallSystemOutput . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-142
ssSetDataTypeSize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-143
ssSetDataTypeZero . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-144
ssSetDWorkComplexSignal . . . . . . . . . . . . . . . . . . . . . . . . . . 10-146
ssSetDWorkDataType . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-147
ssSetDWorkName . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-148
ssSetDWorkRTWIdentifier . . . . . . . . . . . . . . . . . . . . . . . . . . 10-149
ssSetDWorkRTWStorageClass . . . . . . . . . . . . . . . . . . . . . . . 10-150
ssSetDWorkRTWTypeQualifier . . . . . . . . . . . . . . . . . . . . . . 10-151
ssSetDWorkUsedAsDState . . . . . . . . . . . . . . . . . . . . . . . . . . 10-152
ssSetDWorkWidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-153
ssSetErrorStatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-154
ssSetExternalModeFcn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-155
ssSetInputPortComplexSignal . . . . . . . . . . . . . . . . . . . . . . . 10-156
ssSetInputPortDataType . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-157
ssSetInputPortDimensionInfo . . . . . . . . . . . . . . . . . . . . . . . . 10-158
ssSetInputPortDirectFeedThrough . . . . . . . . . . . . . . . . . . . . 10-160
ssSetInputPortFrameData . . . . . . . . . . . . . . . . . . . . . . . . . . 10-161
ssSetInputPortMatrixDimensions . . . . . . . . . . . . . . . . . . . . 10-162
ssSetInputPortOffsetTime . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-163
ssSetInputPortOverWritable . . . . . . . . . . . . . . . . . . . . . . . . . 10-164
ssSetInputPortRequiredContiguous . . . . . . . . . . . . . . . . . . . 10-165
ssSetInputPortReusable . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-166
ssSetInputPortSampleTime . . . . . . . . . . . . . . . . . . . . . . . . . 10-168
ssSetInputPortSampleTimeIndex . . . . . . . . . . . . . . . . . . . . . 10-169
ssSetInputPortVectorDimension . . . . . . . . . . . . . . . . . . . . . . 10-170
ssSetInputPortWidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-171
ssSetIWorkValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-172
ssSetModeVectorValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-173
ssSetNumContStates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-174
ssSetNumDiscStates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-175
ssSetNumDWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-176
ssSetNumInputPorts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-177
ssSetNumIWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-178
ssSetNumModes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-179
ssSetNumNonsampledZCs . . . . . . . . . . . . . . . . . . . . . . . . . . 10-180
ssSetNumOutputPorts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-181
ssSetNumPWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-182
ssSetNumRunTimeParams . . . . . . . . . . . . . . . . . . . . . . . . . . 10-183
ssSetNumRWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-184
ssSetNumSampleTimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-185
ssSetNumSFcnParams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-186
ssSetOffsetTime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-187
ssSetOptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-188
xi
xii Contents
ssSetOutputPortComplexSignal . . . . . . . . . . . . . . . . . . . . . . 10-192
ssSetOutputPortDataType . . . . . . . . . . . . . . . . . . . . . . . . . . 10-193
ssSetOutputPortDimensionInfo . . . . . . . . . . . . . . . . . . . . . . 10-194
ssSetOutputPortFrameData . . . . . . . . . . . . . . . . . . . . . . . . . 10-195
ssSetOutputPortMatrixDimensions . . . . . . . . . . . . . . . . . . . 10-196
ssSetOutputPortOffsetTime . . . . . . . . . . . . . . . . . . . . . . . . . 10-197
ssSetOutputPortReusable . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-198
ssSetOutputPortSampleTime . . . . . . . . . . . . . . . . . . . . . . . . 10-200
ssSetOutputPortVectorDimension . . . . . . . . . . . . . . . . . . . . 10-201
ssSetOutputPortWidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-202
ssSetParameterName . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-203
ssSetParameterTunable . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-204
ssSetPlacementGroup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-205
ssSetPWorkValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-206
ssSetRWorkValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-207
ssSetRunTimeParamInfo . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-208
ssSetSampleTime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-211
ssSetSFcnParamNotTunable . . . . . . . . . . . . . . . . . . . . . . . . 10-212
ssSetSFcnParamTunable . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-213
ssSetSolverNeedsReset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-214
ssSetStopRequested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-216
ssSetTNext . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-217
ssSetUserData . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-218
ssSetVectorMode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-219
ssUpdateAllTunableParamsAsRunTimeParams . . . . . . . . . 10-220
ssUpdateRunTimeParamData . . . . . . . . . . . . . . . . . . . . . . . 10-221
ssUpdateDlgParamAsRunTimeParam . . . . . . . . . . . . . . . . . 10-222
ssUpdateRunTimeParamInfo . . . . . . . . . . . . . . . . . . . . . . . . 10-223
ssWarning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-224
ssWriteRTW2dMatParam . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-225
ssWriteRTWMx2dMatParam . . . . . . . . . . . . . . . . . . . . . . . . 10-226
ssWriteRTWMxVectParam . . . . . . . . . . . . . . . . . . . . . . . . . . 10-227
ssWriteRTWParameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-228
ssWriteRTWParamSettings . . . . . . . . . . . . . . . . . . . . . . . . . 10-232
ssWriteRTWScalarParam . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-236
ssWriteRTWStr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-237
ssWriteRTWStrParam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-238
ssWriteRTWStrVectParam . . . . . . . . . . . . . . . . . . . . . . . . . . 10-239
ssWriteRTWVectParam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-240
ssWriteRTWWorkVect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-241
1
Overview of S-Functions
S-functions (system-functions) provide a powerful mechanism for extending the capabilities of
Simulink
?
. The following sections explain what an S-function is and when and why you might use
one and how to write your own S-functions.
What Is an S-Function? (p. 1-2) Brief overview of S-functions.
Using S-Functions in Models (p. 1-3) How to insert S-functions as blocks in a model and pass
parameters to them.
How S-Functions Work (p. 1-6) How Simulink invokes S-functions when simulating a
model that includes them.
Implementing S-Functions (p. 1-10) How to write S-functions.
S-Function Concepts (p. 1-13) Some key concepts needed to write certain types of
S-functions.
S-Function Examples (p. 1-18) Examples that illustrate the creation of various types of
S-functions and S-function features.
1 Overview of S-Functions
1-2
What Is an S-Function?
An S-function is a computer language description of a Simulink block.
S-functions can be written in MATLAB, C, C++, Ada, or Fortran. C, C++, Ada,
and Fortran S-functions are compiled as MEX-files using the mex utility (see
“Building MEX-Files” in the online MATLAB documentation). As with other
MEX-files, they are dynamically linked into MATLAB when needed.
S-functions use a special calling syntax that enables you to interact with
Simulink’s equation solvers. This interaction is very similar to the interaction
that takes place between the solvers and built-in Simulink blocks. The form of
an S-function is very general and can accommodate continuous, discrete, and
hybrid systems.
S-functions allow you to add your own blocks to Simulink models. You can
create your blocks in MATLAB
?
, C, C++, Fortran, or Ada. By following a set of
simple rules, you can implement your algorithms in an S-function. After you
write your S-function and place its name in an S-Function block (available in
the Functions & Tables block library), you can customize the user interface by
using masking.
You can use S-functions with the Real-Time Workshop
?
. You can also
customize the code generated by the Real Time Workshop for S-functions by
writing a Target Language Compiler
TM
(TLC) file. See “Writing S-Functions for
Real-Time Workshop” on page 8-1 and the Real-Time Workshop
documentation for more information.
Using S-Functions in Models
Using S-Functions in Models
To incorporate an S-function into an Simulink model, drag an S-Function block
from Simulink’s Functions & Tables block library into the model. Then specify
the name of the S-function in the S-function name field of the S-Function
block’s dialog box, as illustrated in the following figure.
Figure 1-1: Relationship Between an S-Function Block, Its Dialog Box,
and the Source File That Defines the Block’s Behavior
In this example, the model contains two instances of an S-Function block. Both
blocks reference the same source file (mysfun, which can be either a C MEX-file
or an M-file). If both a C MEX-file and an M-file have the same name, the C
MEX-file takes precedence and is the file that the S-function uses.
S-Function1 dialog box
/*
* MYSFUN
*
*/
/* The follo
#define S_FU
.
.
.
function[sys
% mysfun M-file
%
switch(flag)
.
.
.
S-function dialog box
A model that includes two
S-function blocks
S-function source file
C MEX file
or
M file
1-3
1 Overview of S-Functions
1-4
Passing Parameters to S-Functions
The S-function block’s S-function parameters field allows you to specify
parameter values to be passed to the corresponding S-function. To use this
field, you must know the parameters the S-function requires and the order in
which the function requires them. (If you do not know, consult the S-function’s
author, documentation, or source code.) Enter the parameters, separated by a
comma, in the order required by the S-function. The parameter values can be
constants, names of variables defined in the model’s workspace, or MATLAB
expressions.
The following example illustrates usage of the S-function parameters field to
enter user-defined parameters.
The model in this example incorporates limintm, a sample S-function that
comes with Simulink. The function’s source code resides in
toolbox/simulink/blocks. The limintm function accepts three parameters: a
lower bound, an upper bound, and an initial condition. It outputs the time
integral of the input signal if the time integral is between the lower and upper
bounds, the lower bound if the time integral is less than the lower bound, and
the upper bound if the time integral is greater than the upper bound. The
dialog box in the example specifies a lower and upper bound and an initial
condition of 2, 3, and 2.5, respectively. The scope shows the resulting output
when the input is a sine wave of amplitude 1.
Using S-Functions in Models
See “Processing S-Function Parameters” on page 2-6 and “Handling Errors” on
page 7-33 for information on how to access user-specified parameters in an
S-function.
You can use Simulink’s masking facility to create custom dialog boxes and
icons for your S-function blocks. Masked dialog boxes can make it easier to
specify additional parameters for S-functions. For discussions of additional
parameters and masking, see Using Simulink.
When to Use an S-Function
The most common use of S-functions is to create custom Simulink blocks. You
can use S-functions for a variety of applications, including
? Adding new general purpose blocks to Simulink
Adding blocks that represent hardware device drivers
Incorporating existing C code into a simulation
Describing a system as a set of mathematical equations
Using graphical animations (see the inverted pendulum demo, penddemo)
An advantage of using S-functions is that you can build a general purpose block
that you can use many times in a model, varying parameters with each
instance of the block.
1-5
1 Overview of S-Functions
1-6
How S-Functions Work
To create S-functions, you need to know how S-functions work. Understanding
how S-functions work, in turn, requires understanding how Simulink
simulates a model, and this, in turn requires an understanding of the
mathematics of blocks. This section therefore begins by explaining the
mathematical relationship between a block’s inputs, states, and outputs.
Mathematics of Simulink Blocks
A Simulink block consists of a set of inputs, a set of states, and a set of outputs,
where the outputs are a function of the sample time, the inputs, and the block’s
states.
The following equations express the mathematical relationships between the
inputs, outputs, and the states.
Simulation Stages
Execution of a Simulink model proceeds in stages. First comes the
initialization phase. In this phase, Simulink incorporates library blocks into
the model, propagates widths, data types, and sample times, evaluates block
parameters, determines block execution order, and allocates memory. Then
Simulink enters a simulation loop, where each pass through the loop is referred
x
(states)
uy
(input) (output)
(Output)
(Derivative)
(Update)
where xx
c
x
d
+=
yf
0
txu,,()=
x
·
c
f
d
txu,,()=
x
d
k 1+
f
u
txu,,()=
How S-Functions Work
to as a simulation step. During each simulation step, Simulink executes each
of the model’s blocks in the order determined during initialization. For each
block, Simulink invokes functions that compute the block’s states, derivatives,
and outputs for the current sample time. This continues until the simulation is
complete.
1-7
1 Overview of S-Functions
1-8
The following figure illustrates the stages of a simulation.
Figure 1-2: How Simulink Performs Simulation
Initialize model
Clean up at final
time step
Calculate time of next sample hit
(only for variable sample time blocks)
Calculate outputs
Update discrete states
Integration
(minor time step)
Calculate derivatives
Calculate derivatives
Locate zero crossings
Calculate outputs
Calculate derivatives
Si
m
u
l
a
ti
on
l
o
o
p
How S-Functions Work
S-Function Callback Methods
An S-function comprises a set of S-function callback methods that perform
tasks required at each simulation stage. During simulation of a model, at each
simulation stage, Simulink calls the appropriate methods for each S-function
block in the model. Tasks performed by S-function methods include
Initialization — Prior to the first simulation loop, Simulink initializes the
S-function. During this stage, Simulink
- Initializes the SimStruct, a simulation structure that contains
information about the S-function
- Sets the number and dimensions of input and output ports
- Sets the block sample times
- Allocates storage areas and the sizes array
Calculation of next sample hit — If you’ve created a variable sample time
block, this stage calculates the time of the next sample hit; that is, it
calculates the next step size.
Calculation of outputs in the major time step — After this call is complete,
all the output ports of the blocks are valid for the current time step.
Update of discrete states in the major time step — In this call, all blocks
should perform once-per-time-step activities such as updating discrete states
for next time around the simulation loop.
Integration — This applies to models with continuous states and/or
nonsampled zero crossings. If your S-function has continuous states,
Simulink calls the output and derivative portions of your S-function at minor
time steps. This is so Simulink can compute the states for your S-function. If
your S-function (C MEX only) has nonsampled zero crossings, Simulink calls
the output and zero-crossings portions of your S-function at minor time steps
so that it can locate the zero crossings.
Note See “How Simulink Works” in the Using Simulink documentation for
an explanation of major and minor time steps.
1-9
1 Overview of S-Functions
1-10
Implementing S-Functions
You can implement an S-function as either an M-file or a MEX file. The
following sections describe these alternative implementations and discuss the
advantages of each.
M-File S-Functions
An M-file S-function consists of a MATLAB function of the following form:
[sys,x0,str,ts]=f(t,x,u,flag,p1,p2,...)
where f is the S-function’s name, t is the current time, x is the state vector of
the corresponding S-function block, u is the block’s inputs, flag indicates a task
to be performed, and p1, p2, ... are the block’s parameters. During simulation
of a model, Simulink repeatedly invokes f, using flag to indicate the task to be
performed for a particular invocation. Each time the S-function performs the
task, it returns the result in a structure having the format shown in the syntax
example.
A template implementation of an M-file S-function, sfuntmpl.m, resides in
matlabroot/toolbox/simulink/blocks. The template consists of a top-level
function and a set of skeleton subfunctions, each of which corresponds to a
particular value of flag. The top-level function invokes the subfunction
indicated by flag. The subfunctions, called S-function callback methods,
perform the tasks required of the S-function during simulation. The following
table lists the contents of an M-file S-function that follows this standard
format.
Simulation Stage S-Function Routine Flag
Initialization mdlInitializeSizes flag = 0
Calculation of next sample
hit (variable sample time
block only)
mdlGetTimeOfNextVarHit flag = 4
Calculation of outputs mdlOutputs flag = 3
Update of discrete states mdlUpdate flag = 2
Implementing S-Functions
We recommend that you follow the structure and naming conventions of the
template when creating M-file S-functions. This makes it easier for others to
understand and maintain M-file S-functions that you create. See Chapter 2,
“Writing M S-Functions,” for information on creating M-file S-functions.
MEX-File S-Functions
Like an M-file S-function, a MEX-file function consists of a set of callback
routines that Simulink invokes to perform various block-related tasks during
a simulation. Significant differences exist, however. For one, MEX-file
functions are implemented in a different programming language: C, C++, Ada,
or Fortran. Also, Simulink invokes MEX S-function routines directly instead of
via a flag value as with M-file S-functions. Because Simulink invokes the
functions directly, MEX-file functions must follow standard naming
conventions specified by Simulink.
Other key differences exist. For one, the set of callback functions that MEX
functions can implement is much larger than can be implemented by M-file
functions. A MEX function also has direct access to the internal data structure,
called the SimStruct, that Simulink uses to maintain information about the
S-function. MEX-file functions can also use the MATLAB MEX-file API to
access the MATLAB workspace directly.
A C MEX-file S-function template, called sfuntmpl_basic.c, resides in the
matlabroot/simulink/src directory. The template contains skeleton
implementations of all the required and optional callback routines that a C
MEX-file S-function can implement. For a more amply commented version of
the template, see sfuntmpl_doc.c in the same directory.
MEX-File Versus M-File S-Functions
M-file and MEX-file S-functions each have advantages. The advantage of M-file
S-functions is speed of development. Developing M-file S-functions avoids the
time-consuming compile-link-execute cycle required by development in a
compiled language. M-file S-functions also have easier access to MATLAB and
Calculation of derivatives mdlDerivatives flag = 1
End of simulation tasks mdlTerminate flag = 9
Simulation Stage S-Function Routine Flag
1-11
toolbox functions.
1 Overview of S-Functions
1-12
The primary advantage of MEX-file functions is versatility. The larger number
of callbacks and access to the SimStruct enable MEX-file functions to
implement functionality not accessible to M-file S-functions. Such functionality
includes the ability to handle data types other than double, complex inputs,
matrix inputs, and so on.
S-Function Concepts
S-Function Concepts
Understanding these key concepts should enable you to build S-functions
correctly:
Direct feedthrough
Dynamically sized inputs
Setting sample times and offsets
Direct Feedthrough
Direct feedthrough means that the output (or the variable sample time for
variable sample time blocks) is controlled directly by the value of an input port.
A good rule of thumb is that an S-function input port has direct feedthrough if
The output function (mdlOutputs or flag==3) is a function of the input u.
That is, there is direct feedthrough if the input u is accessed in mdlOutputs.
Outputs can also include graphical outputs, as in the case of an XY Graph
scope.
The “time of next hit” function (mdlGetTimeOfNextVarHit or flag==4) of a
variable sample time S-function accesses the input u.
An example of a system that requires its inputs (i.e., has direct feedthrough) is
the operation , where u is the input, k is the gain, and y is the output.
An example of a system that does not require its inputs (i.e., does not have
direct feedthrough) is this simple integration algorithm
Outputs:
Derivative:
where x is the state, is the state derivative with respect to time, u is the
input, and y is the output. Note that is the variable that Simulink integrates.
It is very important to set the direct feedthrough flag correctly because it
affects the execution order of the blocks in your model and is used to detect
algebraic loops.
Dynamically Sized Arrays
S-functions can be written to support arbitrary input dimensions. In this case,
yku×=
yx=
x
·
u=
x
·
x
·
1-13
the actual input dimensions are determined dynamically when a simulation is
1 Overview of S-Functions
1-14
started by evaluating the dimensions of the input vector driving the S-function.
The input dimensions can also be used to determine the number of continuous
states, the number of discrete states, and the number of outputs.
M-file S-functions can have only one input port and that input port can accept
only one-dimensional (vector) signals. However, the signals can be of varying
widths.Within an M-file S-function, to indicate that the input width is
dynamically sized, specify a value of -1 for the appropriate fields in the sizes
structure, which is returned during the mdlInitializeSizes call. You can
determine the actual input width when your S-function is called by using
length(u). If you specify a width of 0, the input port is removed from the
S-function block.
A C S-function can have multiple I/O ports and the ports can have different
dimensions. The number of dimensions and the size of each dimension can be
determined dynamically.
For example, the following illustration shows two instances of the same
S-Function block in a model.
The upper S-Function block is driven by a block with a three-element output
vector. The lower S-Function block is driven by a block with a scalar output. By
specifying that the S-Function block has dynamically sized inputs, the same
S-function can accommodate both situations. Simulink automatically calls the
block with the appropriately sized input vector. Similarly, if other block
characteristics, such as the number of outputs or the number of discrete or
continuous states, are specified as dynamically sized, Simulink defines these
vectors to be the same length as the input vector.
C S-functions give you more flexibility in specifying the widths of input and
output ports. See “Creating Input and Output Ports” on page 7-8.
S-Function Concepts
Setting Sample Times and Offsets
Both M-file and C MEX S-functions allow a high degree of flexibility in
specifying when an S-function executes. Simulink provides the following
options for sample times:
Continuous sample time — For S-functions that have continuous states
and/or nonsampled zero crossings (see “How Simulink Works” in Using
Simulink for explanation of zero crossings). For this type of S-function, the
output changes in minor time steps.
Continuous but fixed in minor time step sample time — For S-functions that
need to execute at every major simulation step, but do not change value
during minor time steps.
Discrete sample time — If your S-Function block’s behavior is a function of
discrete time intervals, you can define a sample time to control when
Simulink calls the block. You can also define an offset that delays each
sample time hit. The value of the offset cannot exceed the corresponding
sample time.
A sample time hit occurs at time values determined by the formula
TimeHit = (n * period) + offset
where n, an integer, is the current simulation step. The first value of n is
always zero.
If you define a discrete sample time, Simulink calls the S-function mdlOutput
and mdlUpdate routines at each sample time hit (as defined in the above
equation).
Variable sample time — A discrete sample time where the intervals between
sample hits can vary. At the start of each simulation step, S-functions with
variable sample times are queried for the time of the next hit.
Inherited sample time — Sometimes an S-Function block has no inherent
sample time characteristics (that is, it is either continuous or discrete,
depending on the sample time of some other block in the system). You can
specify that the block’s sample time is inherited. A simple example of this is
a Gain block that inherits its sample time from the block driving it.
A block can inherit its sample time from
- The driving block
1-15
- The destination block
1 Overview of S-Functions
1-16
- The fastest sample time in the system
To set a block’s sample time as inherited, use -1 in M-file S-functions and
INHERITED_SAMPLE_TIME in C S-functions as the sample time. For more
information on the propagation of sample times, see “Sample Time Colors” in
Using Simulink.
S-functions can be either single or multirate; a multirate S-function has
multiple sample times.
Sample times are specified in pairs in this format: [sample_time,
offset_time]. The valid sample time pairs are
[CONTINUOUS_SAMPLE_TIME, 0.0]
[CONTINUOUS_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]
[discrete_sample_time_period, offset]
[VARIABLE_SAMPLE_TIME, 0.0]
where
CONTINUOUS_SAMPLE_TIME = 0.0
FIXED_IN_MINOR_STEP_OFFSET = 1.0
VARIABLE_SAMPLE_TIME = -2.0
and the italics indicate that a real value is required.
Alternatively, you can specify that the sample time is inherited from the
driving block. In this case the S-function can have only one sample time pair
[INHERITED_SAMPLE_TIME, 0.0]
or
[INHERITED_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]
where
INHERITED_SAMPLE_TIME = -1.0
The following guidelines might help you specify sample times:
A continuous S-function that changes during minor integration steps should
register the [CONTINUOUS_SAMPLE_TIME, 0.0] sample time.
A continuous S-function that does not change during minor integration steps
should register the
[CONTINUOUS_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET] sample time.
S-Function Concepts
A discrete S-function that changes at a specified rate should register the
discrete sample time pair, [discrete_sample_time_period, offset],
where
discrete_sample_period > 0.0
and
0.0 ≤ offset < discrete_sample_period
A discrete S-function that changes at a variable rate should register the
variable step discrete sample time.
[VARIABLE_SAMPLE_TIME, 0.0]
The mdlGetTimeOfNextVarHit routine is called to get the time of the next
sample hit for the variable step discrete task.
If your S-function has no intrinsic sample time, you must indicate that your
sample time is inherited. There are two cases:
An S-function that changes as its input changes, even during minor
integration steps, should register the [INHERITED_SAMPLE_TIME, 0.0]
sample time.
An S-function that changes as its input changes, but doesn’t change during
minor integration steps (that is, remains fixed during minor time steps),
should register the
[INHERITED_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET] sample time.
The Scope block is a good example of this type of block. This block should run
at the rate of its driving block, either continuous or discrete, but should never
run in minor steps. If it did, the scope display would show the intermediate
computations of the solver rather than the final result at each time point.
1-17
1 Overview of S-Functions
1-18
S-Function Examples
Simulink comes with a library of S-function examples.
To run an example:
1 Enter sfundemos at the MATLAB command line.
MATLAB displays the S-function demo library.
Each block represents an S-function example.
2 Click a block to open and run the example that it represents.
It might be helpful to examine some sample S-functions as you read the next
chapters. Code for the examples is stored in these subdirectories under the
MATLAB root directory:
M-files toolbox/simulink/blocks
C, C++, and Fortran simulink/src
Ada simulink/ada/examples
S-Function Examples
M-File S-Function Examples
The simulink/blocks directory contains many M-file S-functions. Consider
starting off by looking at these files.
Filename Description
csfunc.m Define a continuous system in state-space format.
dsfunc.m Define a discrete system in state-space format.
vsfunc.m Illustrates how to create a variable sample time block.
This block implements a variable step delay in which
the first input is delayed by an amount of time
determined by the second input.
mixed.m Implement a hybrid system consisting of a continuous
integrator in series with a unit delay.
vdpm.m Implement the Van der Pol equation (similar to the
demo model, vdp).
simom.m Example state-space M-file S-function with internal A,
B, C, and D matrices. This S-function implements
dx/at = Ax + By
y = Cx + Du
where x is the state vector, u is the input vector, and y
is the output vector. The A, B, C, and D matrices are
embedded in the M-file.
simom2.m Example state-space M-file S-function with external A,
B, C, and D matrices. The state-space structure is the
same as in simom.m, but the A, B, C, and D matrices are
provided externally as parameters to this file.
limintm.m Implement a continuous limited integrator where the
output is bounded by lower and upper bounds and
includes initial conditions.
sfun_varargm.m Example M-file S-function showing how to use the
MATLAB vararg facility.
1-19
1 Overview of S-Functions
1-20
C S-Function Examples
The simulink/src directory also contains examples of C MEX S-functions,
many of which have an M-file S-function counterpart. These C MEX
S-functions are listed in this table.
vlimintm.m Example of a continuous limited integrator S-function.
This illustrates how to use the size entry of ?1 to build
an S-function that can accommodate a dynamic
input/state width.
vdlimintm.m Example of a discrete limited integrator S-function.
This example is identical to vlimint.m, except that the
limited integrator is discrete.
Filename Description
barplot.c Access simulink signals without using the
standard block inputs.
csfunc.c Example C MEX S-function for defining a
continuous system.
dlimint.c Implement a discrete-time limited integrator.
dsfunc.c Example C MEX S-function for defining a discrete
system.
fcncallgen.c Execute function-call subsystems n times at the
designated rate (sample time).
limintc.c Implement a limited integrator.
mixedm.c Implement a hybrid dynamic system consisting of
a continuous integrator (1/s) in series with a unit
delay (1/z).
mixedmex.c Implement a hybrid dynamic system with a single
output and two inputs.
Filename Description
S-Function Examples
quantize.c Example MEX-file for a vectorized quantizer
block. Quantizes the input into steps as specified
by the quantization interval parameter, q.
resetint.c A reset integrator.
sdotproduct Compute dot product (multiply-accumulate) of
two real or complex vectors.
sftable2.c Two-dimensional table lookup in S-function form.
sfun_atol.c Set different absolute tolerances for each
continuous state.
sfun_bitop.c Perform the bitwise operations AND, OR, XOR, left
shift, right shift, and one’s complement on uint8,
uint16, and uint32 inputs.
sfun_cplx.c Complex signal add with one input port and one
parameter.
sfun_directlook.c Direct 1-D lookup.
sfun_dtype_io.c Example of the use of Simulink data types for
inputs and outputs.
sfun_dtype_param.c Example of the use of Simulink data types for
parameters.
sfun_dynsize.c Simple example of how to size outputs of an
S-function dynamically.
sfun_errhdl.c Simple example of how to check parameters using
the mdlCheckParams S-function routine.
sfun_fcncall.c Example of an S-function that is configured to
execute function-call subsystems on the first and
third output elements.
sfun_frmad.c Frame-based A/D converter.
Filename Description
1-21
1 Overview of S-Functions
1-22
sfun_frmda.c Frame-based D/A converter.
sfun_frmdft.c Multichannel frame-based Discrete-Fourier
transformation (and its inverse).
sfun_frmunbuff.c Frame-based unbuffer block.
sfun_multiport.c S-function that has multiple input and output
ports.
sfun_manswitch.c Manual switch.
sfun_matadd.c Matrix add with one input port, one output port,
and one parameter.
sfun_multirate.c Demonstrate how to specify port-based sample
times.
sfun_psbbreaker.c Implement the logic for the breaker block in the
Power System Blockset.
sfun_psbcontc.c Continuous implementation of state-space system.
sfun_psbdiscc.c Discrete implementation of state-space system.
sfun_runtime1.c Run-time parameter example.
sfun_runtime2.c Run-time parameter example.
sfun_zc.c Demonstrate use of nonsampled zero crossings to
implement abs(u). This S-function is designed to
be used with a variable-step solver.
sfun_zc_sat.c Saturation example that uses zero crossings.
sfunmem.c A one-integration-step delay and hold memory
function.
Filename Description
S-Function Examples
simomex.c Implements a single-output, two-input state-space
dynamic system described by these state-space
equations
dx/dt = Ax + Bu
y = Cx + Du
where x is the state vector, u is vector of inputs,
and y is the vector of outputs.
smatrxcat.c Matrix concatenation.
sreshape.c Reshape the input signal.
stspace.c Implement a set of state-space equations. You can
turn this into a new block by using the S-Function
block and mask facility. This example MEX-file
performs the same function as the built-in
State-Space block. This is an example of a
MEX-file where the number of inputs, outputs,
and states is dependent on the parameters passed
in from the workspace. Use this as a template for
other MEX-file systems.
stvctf.c Implement a continuous-time transfer function
whose transfer function polynomials are passed in
via the input vector. This is useful for continuous
time adaptive control applications.
stvdct.f Implement a discrete-time transfer function
whose transfer function polynomials are passed in
via the input vector. This is useful for
discrete-time adaptive control applications.
stvmgain.c Time-varying matrix gain.
table3.c 3-D lookup table.
timestwo.c Basic C MEX S-function that doubles its input.
Filename Description
1-23
1 Overview of S-Functions
1-24
Fortran S-Function Examples
The following table lists sample Fortran S-functions.
C++ S-Function Examples
The following table lists sample C++ S-functions.
vdlmint.c Implement a discrete-time vectorized limited
integrator.
vdpmex.c Implement the Van der Pol equation.
vlimint.c Implement a vectorized limited integrator.
vsfunc.c Illustrate how to create a variable sample time
block in Simulink. This block implements a
variable-step delay in which the first input is
delayed by an amount of time determined by the
second input.
Filename Description
sfun_timestwo_for.
for
Sample Level 1 Fortran representation of a C
timestwo S-function.
sfun_atmos.c Calculation of the 1976 standard atmosphere to
86 km.
vdpmexf.for Van der Pol system.
Filename Description
sfun_counter_cpp.cpp Store a C++ object in the pointers vector PWork.
Filename Description
S-Function Examples
Ada S-Function Examples
The simulink/ada/examples directory contains the following examples of
S-functions implemented in Ada.
Directory Name Description
matrix_gain Implement a Matrix Gain block.
multi_port Multiport block.
simple_lookup Lookup table. Illustrates use of a wrapper
S-function that wraps stand-alone Ada code (i.e.,
Ada packages and procedures) both for use with
Simulink as an S-function and directly with Ada
code generated using the RTW Ada Coder.
times_two Output twice its input.
1-25
1 Overview of S-Functions
1-26
2
Writing M S-Functions
The following sections explain how to use the M programming language to create S-functions.
Introduction (p. 2-2) Explains the syntax of an M S-function.
Defining S-Function Block
Characteristics (p. 2-5)
How to specify the number of states, inputs and outputs,
and other attributes of the block implemented by the M
S-function.
Processing S-Function Parameters
(p. 2-6)
How to process block parameters passed to the M
S-function.
Examples of M-File S-Functions
(p. 2-7)
Examples of M S-functions that implement various types
of blocks.
2 Writing M S-Functions
2-2
Introduction
An M-file S-function consists of a MATLAB function of the following form
[sys,x0,str,ts]=f(t,x,u,flag,p1,p2,...)
where f is the name of the S-function. During simulation of a model, Simulink
repeatedly invokes f, using the flag argument to indicate the task (or tasks)
to be performed for a particular invocation. Each time the S-function performs
the task and returns the results in an output vector.
A template implementation of an M-file S-function, sfuntmpl.m, resides in
matlabroot/toolbox/simulink/blocks. The template consists of a top-level
function and a set of skeleton subfunctions, called S-function callback methods,
each of which corresponds to a particular value of flag. The top-level function
invokes the subfunction indicated by flag. The subfunctions perform the
actual tasks required of the S-function during simulation.
S-Function Arguments
Simulink passes the following arguments to an S-function:
t Current time
x State vector
u Input vector
flag Integer value that indicates the task to be performed by the
S-function
Introduction
The following table describes the values that flag can assume and lists the
corresponding S-function method for each value.
S-Function Outputs
An M-file returns an output vector containing the following elements:
sys, a generic return argument. The values returned depend on the flag
value. For example, for flag = 3, sys contains the S-function outputs.
x0, the initial state values (an empty vector if there are no states in the
system). x0 is ignored, except when flag = 0.
Table 2-1: Flag Argument
Flag S-Function Routine Description
0 mdlInitializeSizes Defines basic S-Function block
characteristics, including sample
times, initial conditions of
continuous and discrete states, and
the sizes array.
1 mdlDerivatives Calculates the derivatives of the
continuous state variables.
2 mdlUpdate Updates discrete states, sample
times, and major time step
requirements.
3 mdlOutputs Calculates the outputs of the
S-function.
4 mdlGetTimeOfNextVarHit Calculates the time of the next hit
in absolute time. This routine is
used only when you specify a
variable discrete-time sample time
in mdlInitializeSizes.
9 mdlTerminate Performs any necessary
end-of-simulation tasks.
2-3
2 Writing M S-Functions
2-4
str, reserved for future use. M-file S-functions must set this to the empty
matrix, [].
ts, a two-column matrix containing the sample times and offsets of the block
(see “Specifying Sample Time” in the online documentation for information
on how to specify a block’s sample time and offset).
For example, if you want your S-function to run at every time step
(continuous sample time), set ts to [0 0]. If you want your S-function to run
at the same rate as the block to which it is connected (inherited sample time),
set ts to [-1 0]. If you want it to run every 0.25 seconds (discrete sample
time) starting at 0.1 seconds after the simulation start time, set ts to [0.25
0.1].
You can create S-functions that do multiple tasks, each at a different sample
rate (i.e., a multirate S-function). In this case, ts should specify all the
sample rates used by your S-function in ascending order by sample time. For
example, suppose your S-function performs one task every 0.25 second
starting from the simulation start time and another task every 1 second
starting 0.1 second after the simulation start time. In this case, your
S-function should set ts equal to [.25 0; 1.0 .1]. This will cause Simulink
to execute the S-function at the following times: [0 0.1 0.25 0.5 0.75 1
1.1 ...]. Your S-function must decide at every sample time which task to
perform at that sample time.
You can also create an S-function that performs some tasks continuously
(i.e., at every time step) and others at discrete intervals. See “Example -
Hybrid System S-Function” on page 2-14) for an example of how to
implement such a hybrid block.
Defining S-Function Block Characteristics
Defining S-Function Block Characteristics
For Simulink to recognize an M-file S-function, you must provide it with
specific information about the S-function. This information includes the
number of inputs, outputs, states, and other block characteristics.
To give Simulink this information, call the simsizes function at the beginning
of mdlInitializeSizes.
sizes = simsizes;
This function returns an uninitialized sizes structure. You must load the
sizes structure with information about the S-function. The table below lists
the fields of the sizes structure and describes the information contained in
each field.
After you initialize the sizes structure, call simsizes again:
sys = simsizes(sizes);
This passes the information in the sizes structure to sys, a vector that holds
the information for use by Simulink.
Table 2-2: Fields in the sizes Structure
Field Name Description
sizes.NumContStates Number of continuous states
sizes.NumDiscStates Number of discrete states
sizes.NumOutputs Number of outputs
sizes.NumInputs Number of inputs
sizes.DirFeedthrough Flag for direct feedthrough
sizes.NumSampleTimes Number of sample times
2-5
2 Writing M S-Functions
2-6
Processing S-Function Parameters
When invoking an M-file S-function, Simulink always passes the standard
block parameters, t, x, u, and flag, to the S-function as function arguments.
Simulink can pass additional block-specific parameters specified by the user to
the S-function. The user specifies the parameters in the S-function
parameters field of the S-function’s block parameter dialog (see “Passing
Parameters to S-Functions” on page 1-4). If the block dialog specifies additional
parameters, Simulink passes the parameters to the S-function as additional
function arguments. The additional arguments follow the standard arguments
in the S-function argument list in the order in which the corresponding
parameters appear in the block dialog. You can use this block-specific
S-function parameter capability to allow the same S-function to implement
various processing options. See the limintm.m example in the
toolbox/simulink/blocks directory for an example of an S-function that uses
block-specific parameters in this way.
Examples of M-File S-Functions
Examples of M-File S-Functions
The easiest way to understand how S-functions work is to look at examples.
This section starts off with a s simple example (timestwo) that has no states.
Most S-Function blocks require the handling of states, whether continuous or
discrete. The sections that follow discuss four common types of systems you can
model in Simulink using S-functions:
Continuous
Discrete
Hybrid
Variable-step
All examples are based on the M-file S-function template found in sfuntmpl.m.
Simple M-File S-Function Example
This block takes an input scalar signal, doubles it, and plots it to a scope.
The M-file code that contains the S-function is modeled on an S-function
template called sfuntmpl.m, which is included with Simulink. By using this
template, you can create an M-file S-function that is very close in appearance
to a C MEX S-function. This is useful because it makes a transition from an
M-file to a C MEX-file much easier.
Below is the M-file code for the timestwo.m S-function.
function [sys,x0,str,ts] = timestwo(t,x,u,flag)
% Dispatch the flag. The switch function controls the calls to
% S-function routines at each simulation stage.
switch flag,
case 0
[sys,x0,str,ts] = mdlInitializeSizes; % Initialization
case 3
2-7
2 Writing M S-Functions
2-8
sys = mdlOutputs(t,x,u); % Calculate outputs
case { 1, 2, 4, 9 }
sys = []; % Unused flags
otherwise
error(['Unhandled flag = ',num2str(flag)]); % Error handling
end;
% End of function timestwo.
Below are the S-function subroutines that timestwo.m calls.
%==============================================================
% Function mdlInitializeSizes initializes the states, sample
% times, state ordering strings (str), and sizes structure.
%==============================================================
function [sys,x0,str,ts] = mdlInitializeSizes
% Call function simsizes to create the sizes structure.
sizes = simsizes;
% Load the sizes structure with the initialization information.
sizes.NumContStates= 0;
sizes.NumDiscStates= 0;
sizes.NumOutputs= 1;
sizes.NumInputs= 1;
sizes.DirFeedthrough=1;
sizes.NumSampleTimes=1;
% Load the sys vector with the sizes information.
sys = simsizes(sizes);
%
x0 = []; % No continuous states
%
str = []; % No state ordering
%
ts = [-1 0]; % Inherited sample time
% End of mdlInitializeSizes.
%==============================================================
% Function mdlOutputs performs the calculations.
%==============================================================
function sys = mdlOutputs(t,x,u)
sys = 2*u;
Examples of M-File S-Functions
% End of mdlOutputs.
To test this S-function in Simulink, connect a sine wave generator to the input
of an S-Function block. Connect the output of the S-Function block to a Scope.
Double-click the S-Function block to open the dialog box.
You can now run this simulation.
Example - Continuous State S-Function
Simulink includes a function called csfunc.m, which is an example of a
continuous state system modeled in an S-function. Here is the code for the
M-file S-function.
function [sys,x0,str,ts] = csfunc(t,x,u,flag)
% CSFUNC An example M-file S-function for defining a system of
% continuous state equations:
% x' = Ax + Bu
% y = Cx + Du
%
% Generate a continuous linear system:
A=[?0.09 ?0.01
1 0];
B=[ 1 ?7
0 ?2];
C=[ 0 2
Enter the function name here. In this
example, enter timestwo.
If you have additional parameters to
pass to the block, enter their names
here, separating them with commas. In
this example, there are no additional
parameters.
2-9
1 ?5];
2 Writing M S-Functions
2-10
D=[?3 0
1 0];
%
% Dispatch the flag.
%
switch flag,
case 0
[sys,x0,str,ts]=mdlInitializeSizes(A,B,C,D); % Initialization
case 1
sys = mdlDerivatives(t,x,u,A,B,C,D); % Calculate derivatives
case 3
sys = mdlOutputs(t,x,u,A,B,C,D); % Calculate outputs
case { 2, 4, 9 } % Unused flags
sys = [];
otherwise
error(['Unhandled flag = ',num2str(flag)]); % Error handling
end
% End of csfunc.
%==============================================================
% mdlInitializeSizes
% Return the sizes, initial conditions, and sample times for the
% S-function.
%==============================================================
%
function [sys,x0,str,ts] = mdlInitializeSizes(A,B,C,D)
%
% Call simsizes for a sizes structure, fill it in and convert it
% to a sizes array.
%
sizes = simsizes;
sizes.NumContStates = 2;
sizes.NumDiscStates = 0;
sizes.NumOutputs = 2;
sizes.NumInputs = 2;
sizes.DirFeedthrough = 1; % Matrix D is nonempty.
sizes.NumSampleTimes = 1;
Examples of M-File S-Functions
sys = simsizes(sizes);
%
% Initialize the initial conditions.
%
x0 = zeros(2,1);
%
% str is an empty matrix.
%
str = [];
%
% Initialize the array of sample times; in this example the sample
% time is continuous, so set ts to 0 and its offset to 0.
%
ts = [0 0];
% End of mdlInitializeSizes.
%
%==============================================================
% mdlDerivatives
% Return the derivatives for the continuous states.
%==============================================================
function sys = mdlDerivatives(t,x,u,A,B,C,D)
sys = A*x + B*u;
% End of mdlDerivatives.
%
%==============================================================
% mdlOutputs
% Return the block outputs.
%==============================================================
%
function sys = mdlOutputs(t,x,u,A,B,C,D)
sys = C*x + D*u;
% End of mdlOutputs.
The preceding example conforms to the simulation stages discussed earlier in
this chapter. Unlike timestwo.m, this example invokes mdlDerivatives to
calculate the derivatives of the continuous state variables when flag = 1. The
system state equations are of the form
x'= Ax + Bu
y = Cx + Du
2-11
2 Writing M S-Functions
2-12
so that very general sets of continuous differential equations can be modeled
using csfunc.m. Note that csfunc.m is similar to the built-in State-Space block.
This S-function can be used as a starting point for a block that models a
state-space system with time-varying coefficients.
Each time the mdlDerivatives routine is called it must explicitly set the values
of all derivatives. The derivative vector does not maintain the values from the
last call to this routine. The memory allocated to the derivative vector changes
during execution.
Example - Discrete State S-Function
Simulink includes a function called dsfunc.m, which is an example of a discrete
state system modeled in an S-function. This function is similar to csfunc.m, the
continuous state S-function example. The only difference is that mdlUpdate is
called instead of mdlDerivatives. mdlUpdate updates the discrete states when
flag = 2. Note that for a single-rate discrete S-function, Simulink calls the
mdlUpdate, mdlOutputs, and mdlGetTimeOfNextVarHit (if needed) routines
only on sample hits. Here is the code for the M-file S-function.
function [sys,x0,str,ts] = dsfunc(t,x,u,flag)
% An example M-file S-function for defining a discrete system.
% This S-function implements discrete equations in this form:
% x(n+1) = Ax(n) + Bu(n)
% y(n) = Cx(n) + Du(n)
%
% Generate a discrete linear system:
A=[–1.3839 –0.5097
1.0000 0];
B=[–2.5559 0
0 4.2382];
C=[ 0 2.0761
0 7.7891];
D=[ –0.8141 –2.9334
1.2426 0];
switch flag,
case 0
sys = mdlInitializeSizes(A,B,C,D); % Initialization
case 2
Examples of M-File S-Functions
sys = mdlUpdate(t,x,u,A,B,C,D); % Update discrete states
case 3
sys = mdlOutputs(t,x,u,A,B,C,D); % Calculate outputs
case {1, 4, 9} % Unused flags
sys = [];
otherwise
error(['unhandled flag = ',num2str(flag)]); % Error handling
end
% End of dsfunc.
%==============================================================
% Initialization
%==============================================================
function [sys,x0,str,ts] = mdlInitializeSizes(A,B,C,D)
% Call simsizes for a sizes structure, fill it in, and convert it
% to a sizes array.
sizes = simsizes;
sizes.NumContStates = 0;
sizes.NumDiscStates = 2;
sizes.NumOutputs = 2;
sizes.NumInputs = 2;
sizes.DirFeedthrough = 1; % Matrix D is non-empty.
sizes.NumSampleTimes = 1;
sys = simsizes(sizes);
x0 = ones(2,1); % Initialize the discrete states.
str = []; % Set str to an empty matrix.
ts = [1 0]; % sample time: [period, offset]
% End of mdlInitializeSizes.
%==============================================================
% Update the discrete states
%==============================================================
function sys = mdlUpdates(t,x,u,A,B,C,D)
2-13
sys = A*x + B*u;
2 Writing M S-Functions
2-14
% End of mdlUpdate.
%==============================================================
% Calculate outputs
%==============================================================
function sys = mdlOutputs(t,x,u,A,B,C,D)
sys = C*x + D*u;
% End of mdlOutputs.
The above example conforms to the simulation stages discussed earlier in
chapter 1. The system discrete state equations are of the form
x(n+1) = Ax(n) + Bu(n)
y(n) = Cx(n) + Du(n)
so that very general sets of difference equations can be modeled using
dsfunc.m. This is similar to the built-in Discrete State-Space block. You can
use dsfunc.m as a starting point for modeling discrete state-space systems with
time-varying coefficients.
Example - Hybrid System S-Function
Simulink includes a function called mixedm.m, which is an example of a hybrid
system (a combination of continuous and discrete states) modeled in an
S-function. Handling hybrid systems is fairly straightforward; the flag
parameter forces the calls to the correct S-function subroutine for the
continuous and discrete parts of the system. One subtlety of hybrid S-functions
(or any multirate S-function) is that Simulink calls the mdlUpdate,
mdlOutputs, and mdlGetTimeOfNextVarHit routines at all sample times. This
means that in these routines you must test to determine which sample hit is
being processed and only perform updates that correspond to that sample hit.
mixed.m models a continuous Integrator followed by a discrete Unit Delay. In
Simulink block diagram form, the model looks like this.
Here is the code for the M-file S-function.
function [sys,x0,str,ts] = mixedm(t,x,u,flag)
Examples of M-File S-Functions
% A hybrid system example that implements a hybrid system
% consisting of a continuous integrator (1/s) in series with a
% unit delay (1/z).
%
% Set the sampling period and offset for unit delay.
dperiod = 1;
doffset = 0;
switch flag,
case 0 % Initialization
[sys,x0,str,ts] = mdlInitializeSizes(dperiod,doffset);
case 1
sys = mdlDerivatives(t,x,u); % Calculate derivatives
case 2
sys = mdlUpdate(t,x,u,dperiod,doffset); % Update disc states
case 3
sys = mdlOutputs(t,x,u,doffset,dperiod); % Calculate outputs
case {4, 9}
sys = []; % Unused flags
otherwise
error(['unhandled flag = ',num2str(flag)]); % Error handling
end
% End of mixedm.
%
%==============================================================
% mdlInitializeSizes
% Return the sizes, initial conditions, and sample times for the
% S-function.
%==============================================================
function [sys,x0,str,ts] = mdlInitializeSizes(dperiod,doffset)
sizes = simsizes;
sizes.NumContStates = 1;
sizes.NumDiscStates = 1;
sizes.NumOutputs = 1;
sizes.NumInputs = 1;
2-15
sizes.DirFeedthrough = 0;
2 Writing M S-Functions
2-16
sizes.NumSampleTimes = 2;
sys = simsizes(sizes);
x0 = ones(2,1);
str = [];
ts = [0, 0 % sample time
dperiod, doffset];
% End of mdlInitializeSizes.
%
%==============================================================
% mdlDerivatives
% Compute derivatives for continuous states.
%==============================================================
%
function sys = mdlDerivatives(t,x,u)
sys = u;
% end of mdlDerivatives.
%
%==============================================================
% mdlUpdate
% Handle discrete state updates, sample time hits, and major time
% step requirements.
%==============================================================
%
function sys = mdlUpdate(t,x,u,dperiod,doffset)
% Next discrete state is output of the integrator.
% Return next discrete state if we have a sample hit within a
% tolerance of 1e-8. If we don't have a sample hit, return [] to
% indicate that the discrete state shouldn't change.
%
if abs(round((t-doffset)/dperiod)-(t-doffset)/dperiod) < 1e-8
sys = x(1); % mdlUpdate is "latching" the value of the
% continuous state, x(1), thus introducing a delay.
else
sys = []; % This is not a sample hit, so return an empty
end % matrix to indicate that the states have not
% changed.
% End of mdlUpdate.
%
%==============================================================
Examples of M-File S-Functions
% mdlOutputs
% Return the output vector for the S-function.
%==============================================================
%
function sys = mdlOutputs(t,x,u,doffset,dperiod)
% Return output of the unit delay if we have a
% sample hit within a tolerance of 1e-8. If we
% don't have a sample hit then return [] indicating
% that the output shouldn't change.
%
if abs(round((t-doffset)/dperiod)-(t-doffset)/dperiod) < 1e-8
sys = x(2);
else
sys = []; % This is not a sample hit, so return an empty
end % matrix to indicate that the output has not changed
% End of mdlOutputs.
Example - Variable Sample Time S-Function
This M-file is an example of an S-function that uses a variable sample time.
This example, in an M-file called vsfunc.m, calls mdlGetTimeOfNextVarHit
when flag = 4. Because the calculation of a next sample time depends on the
input u, this block has direct feedthrough. Generally, all blocks that use the
input to calculate the next sample time (flag = 4) require direct feedthrough.
Here is the code for the M-file S-function.
function [sys,x0,str,ts] = vsfunc(t,x,u,flag)
% This example S-function illustrates how to create a variable
% step block in Simulink. This block implements a variable step
% delay in which the first input is delayed by an amount of time
% determined by the second input.
%
% dt = u(2)
% y(t+dt) = u(t)
%
switch flag,
case 0
2-17
[sys,x0,str,ts] = mdlInitializeSizes; % Initialization
2 Writing M S-Functions
2-18
case 2
sys = mdlUpdate(t,x,u); % Update Discrete states
case 3
sys = mdlOutputs(t,x,u); % Calculate outputs
case 4
sys = mdlGetTimeOfNextVarHit(t,x,u); % Get next sample time
case { 1, 9 }
sys = []; % Unused flags
otherwise
error(['Unhandled flag = ',num2str(flag)]); % Error handling
end
% End of vsfunc.
%==============================================================
% mdlInitializeSizes
% Return the sizes, initial conditions, and sample times for the
% S-function.
%==============================================================
%
function [sys,x0,str,ts] = mdlInitializeSizes
%
% Call simsizes for a sizes structure, fill it in and convert it
% to a sizes array.
%
sizes = simsizes;
sizes.NumContStates = 0;
sizes.NumDiscStates = 1;
sizes.NumOutputs = 1;
sizes.NumInputs = 2;
sizes.DirFeedthrough = 1; % flag=4 requires direct feedthrough
% if input u is involved in
% calculating the next sample time
% hit.
sizes.NumSampleTimes = 1;
sys = simsizes(sizes);
%
% Initialize the initial conditions.
Examples of M-File S-Functions
%
x0 = [0];
%
% Set str to an empty matrix.
%
str = [];
%
% Initialize the array of sample times.
%
ts = [–2 0]; % variable sample time
% End of mdlInitializeSizes.
%
%==============================================================
% mdlUpdate
% Handle discrete state updates, sample time hits, and major time
% step requirements.
%==============================================================
%
function sys = mdlUpdate(t,x,u)
sys = u(1);
% End of mdlUpdate.
%
%==============================================================
% mdlOutputs
% Return the block outputs.
%==============================================================
%
function sys = mdlOutputs(t,x,u)
sys = x(1);
% end mdlOutputs
%
%==============================================================
% mdlGetTimeOfNextVarHit
% Return the time of the next hit for this block. Note that the
% result is absolute time.
%==============================================================
%
function sys = mdlGetTimeOfNextVarHit(t,x,u)
sys = t + u(2);
2-19
% End of mdlGetTimeOfNextVarHit.
2 Writing M S-Functions
2-20
mdlGetTimeOfNextVarHit returns the time of the next hit, the time in the
simulation when vsfunc is next called. This means that there is no output from
this S-function until the time of the next hit. In vsfunc, the time of the next hit
is set to t + u(2), which means that the second input, u(2), sets the time when
the next call to vsfunc occurs.
3
Writing S-Functions in C
The following sections explain how to use the C programming language to create S-functions.
Introduction (p. 3-2) Overview of writing a C S-function.
Building S-Functions Automatically
(p. 3-5)
How to use the S-Function Builder to generate
S-functions automatically from specifications that you
supply.
Example of a Basic C MEX S-Function
(p. 3-25)
Illustrates the code needed to create a C S-function.
Templates for C S-Functions (p. 3-31) Describes code templates that you can use as
startingpoints for writing your own C S-functions.
How Simulink Interacts with C
S-Functions (p. 3-35)
Describes how Simulink interacts with a C S-function.
This is information that you need to know in order to
create and debug your own C S-functions.
Writing Callback Methods (p. 3-43) How to write methods that Simulink calls as it executes
your S-function.
Converting Level 1 C MEX S-Functions
to Level 2 (p. 3-44)
How to convert S-functions written for earlier releases of
Simulink to work with the current version.
3 Writing S-Functions in C
3-2
Introduction
A C MEX-file that defines an S-Function block must provide information about
the model to Simulink during the simulation. As the simulation proceeds,
Simulink, the ODE solver, and the MEX-file interact to perform specific tasks.
These tasks include defining initial conditions and block characteristics, and
computing derivatives, discrete states, and outputs.
As with M-file S-functions, Simulink interacts with a C MEX-file S-function by
invoking callback methods that the S-function implements. Each method
performs a predefined task, such as computing block outputs, required to
simulate the block whose functionality the S-function defines. Simulink
defines in a general way the task of each callback. The S-function is free to
perform the task according to the functionality it implements. For example,
Simulink specifies that the S-function’s mdlOutput method must compute that
block’s outputs at the current simulation time. It does not specify what those
outputs must be. This callback-based API allows you to create S-functions, and
hence custom blocks, of any desired functionality.
The set of callback methods, hence functionality, that C MEX-files can
implement is much larger than that available for M-file S-functions. See
Chapter 9, “S-Function Callback Methods,” for descriptions of the callback
methods that a C MEX-file S-function can implement. Unlike M-file
S-functions, C MEX-files can access and modify the data structure that
Simulink uses internally to store information about the S-function. The ability
to implement a broader set of callback methods and to access internal data
structures allows C-MEX files to implement a wider set of block features, such
as the ability to handle matrix signals and multiple data types.
C MEX-file S-functions are required to implement only a small subset of the
callback methods that Simulink defines. If your block does not implement a
particular feature, such as matrix signals, you are free to omit the callback
methods required to implement a feature. This allows you to create simple
blocks very quickly.
The general format of a C MEX S-function is shown below.
#define S_FUNCTION_NAME your_sfunction_name_here
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
static void mdlInitializeSizes(SimStruct *S)
Introduction
{
}
<additional S-function routines/code>
static void mdlTerminate(SimStruct *S)
{
}
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a
MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration
function */
#endif
mdlInitializeSizes is the first routine Simulink calls when interacting with
the S-function. Simulink subsequently invokes other S-function methods (all
starting with mdl). At the end of a simulation, Simulink calls mdlTerminate.
Note Unlike M-file S-functions, C MEX S-function methods do not each have
a flag parameter. This is because Simulink calls each S-function method
directly at the appropriate time during the simulation.
Creating C MEX S-Functions
The easiest way to create a C MEX S-function is to use the S-Function Builder
(see “Building S-Functions Automatically” on page 3-5). This tool builds a C
MEX S-function from specifications and code fragments that you supply. This
eliminates the need for you to build the S-function from scratch. The S-function
Builder, however, is limited in the kinds of S-functions that it can build. For
example, it cannot build S-functions that have more than one input or output
or that must handle data types other than double. You must create such
S-functions from scratch.
3-3
3 Writing S-Functions in C
3-4
The following sections provide information on writing C MEX S-functions from
scratch:
“Example of a Basic C MEX S-Function” on page 3-25 provides a step-by-step
example of how to write a simple S-function from scratch.
“Templates for C S-Functions” on page 3-31 describes a complete skeleton
implementation of a C S-function that you can use as a starting point for
creating your own S-functions.
Building S-Functions Automatically
Building S-Functions Automatically
The S-Function Builder is a Simulink block that builds an S-function from
specifications and C code that you supply. The S-Function Builder also serves
as a wrapper for the generated S-function in models that use the S-function.
This section explains how to use the S-Function Builder to build simple C MEX
S-functions.
To build an S-function with the S-Function Builder:
1 Set the MATLAB current directory to the directory in which you want to
create the S-function.
2 Create a new Simulink model.
3 Copy an instance of the S-Function Builder block from the Simulink
User-Defined Functions library into the new model.
4 Double-click the block to open the S-Function Builder dialog box.
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3 Writing S-Functions in C
3-6
5 Enter the name of the S-function in the S-function name field.
6 If the S-function has parameters, enter default values for the parameters in
the S-function parameters field.
7 Use the specification and code entry panes on the S-Function Builder
dialog box to enter information and custom source code required to tailor the
generated S-function to your application (see “S-Function Builder Dialog
Box” on page 3-8).
Building S-Functions Automatically
8 If you have not already done so, configure the MATLAB mex command to
work on your system.
To configure the mex command, type mex -setup at the MATLAB command
line.
9 Click Build on the dialog box to start the build process.
Simulink builds a MEX file that implements the specified S-function and
saves the file in the current directory (see “How the S-Function Builder
Builds an S-Function” on page 3-7).
10 Save the model containing the S-Function Builder block.
Deploying the Generated S-Function
To use the generated S-function in another model, first check to ensure that the
directory containing the generated S-function is on the MATLAB path. Then
copy the S-Function Builder block from the model used to create the S-function
into the target model and set its parameters, if necessary, to the values
required by the target model.
How the S-Function Builder Builds an S-Function
The S-Function Builder builds an S-function as follows. First, it generates the
following source files in the current directory:
sfun.c
where sfun is the name of the S-function that you specified in the S-function
name field of the S-Function Builder’s dialog box. This file contains the C
source code representation of the standard portions of the generated
S-function.
sfun_wrapper.c
This file contains the custom code that you entered in the S-Function
Builder dialog box.
sfun.tlc
This file permits Simulink to run the generated S-function in accelerated
mode and RTW to include this S-function in the code it generates.
After generating the S-function source code, the S-Function Builder uses the
3-7
MATLAB mex command to build the MEX file representation of the S-function
3 Writing S-Functions in C
3-8
from the generated source code and any external custom source code and
libraries that you specified.
S-Function Builder Dialog Box
The tabbed panes on the S-Function Builder dialog box enable you to enter
information and custom code required to tailor the S-function to a specific
application. The dialog box contains the following panes.
Initialization Pane
The Initialization pane allows you to specify basic features of the S-function,
such as the width of its input and output ports and its sample time.
The S-Function Builder uses the information that you enter on this pane to
generate the S-function’s mdlInitializeSizes callback method. Simulink
invokes this method during the model initialization phase of the simulation to
obtain basic information about the S-function. (See “How Simulink Interacts
with C S-Functions” on page 3-35 for more information on the model
initialization phase.)
The Initialization pane contains the following fields.
Number of discrete states. Number of discrete states that the S-function has.
Building S-Functions Automatically
Discrete states IC. Initial conditions of the S-function’s discrete states. You can
enter the values as a comma-separated list or as a vector (e.g., [0 1 2]). The
number of initial conditions must equal the number of discrete states.
Number of continuous states. Number of continuous states that the S-function has.
Continuous states IC. Initial conditions of the S-function’s continuous states. You
can enter the values as a comma-separated list or as a vector (e.g., [0 1 2]).
The number of initial conditions must equal the number of continuous states.
Sample mode. Sample mode of the S-function. The sample mode determines the
length of the interval between the times when the S-function updates its
output. You can select one of the following options:
Inherited
The S-function inherits its sample time from the block connected to its input
port.
Continuous
The block updates its outputs at each simulation step.
Discrete
The S-function updates its outputs at the rate specified in the Discrete
sample time value field of the S-Function Builder dialog box.
Sample time value. Interval between updates of the S-function’s outputs. This
field is enabled only if you have selected Discrete as the S-function’s Sample
time.
Input port width. Width of the S-function’s input port. The width is the number
of elements that a vector signal connected to the port must have. To permit
connection of matrix (2-D) signals to the input port, specify -1 as the input port
width.
Output port width. Width of the S-function’s output port. The width is the
number of elements in the vector that this S-function outputs. If the S-function
outputs matrix signals, specify -1 as the port width.
Number of parameters. Number of parameters that this S-function accepts.
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3 Writing S-Functions in C
3-10
Data Properties Pane
The Data Properties pane allows you to add ports and parameters to your
S-function.
This pane itself contains tabbed panes that respectively display the attributes
of the S-function’s
Input ports (see “Input Ports Pane” on page 3-11)
Output ports (see “Output Ports Pane” on page 3-12)
Parameters (see “Parameters Pane” on page 3-13),
The column of buttons to the left of the panes allows you to add, delete, or
reorder ports or parameters, depending on the currently selected pane.
To add add a port or parameter, click the Add button (the top button in the
column of buttons).
To delete the currently selected port/parameter , click the Delete button
(located beneath the Add button).
To move the currently selected port/parameter up one position in the
corresponding S-Function port/parameter list, click the Up button (beneath
the Delete button).
Building S-Functions Automatically
To move the currently selected port/parameter down one position in the
corresponding S-function port/parameter list, click the Down button
(beneath the Up button).
Input Ports Pane
The Input Ports pane allows you to inspect and modify the properties of the
S-function’s input ports.
The pane comprises an editable table that lists the properties of the input ports
in the order in which the ports appear on the S-function block. Each row of the
table corresponds to a port. Each entry in the row displays a property of the
port as follows.
Port name. Name of the port. Edit this field to change the port name.
Data type. Lists the data type of signals accepted by the port. Click the adjacent
button to display a list of supported data types. To change the port’s data type,
select a new type from the list.
Dimensions. Lists the number of dimensions of input signals accepted by the
port. To display a list of supported dimensions, click the adjacent button. To
change the port’s dimensionality, select a new value from the list. (Simulink
signals can have at most two dimensions).
Row. Specifies the size of the input signal’s first (or only) dimension.
Column. Specifies the size of the input signal’s second dimension (only if the
input port accepts 2-D signals).
Complexity. Specifies whether the input port accepts real or complex-valued
signals.
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3 Writing S-Functions in C
3-12
Frame. Specifies whether this port accepts frame-based signals generated by
the Digital and Signal Processing Blockset and Communications Blockset. See
the documentation for these blocksets for more information.
Output Ports Pane
The Output Ports pane allows you to inspect and modify the properties of the
S-function’s output ports.
The pane comprises an editable table that lists the properties of the output
ports in the order in which the ports appear on the S-function block. Each row
of the table corresponds to a port. Each entry in the row displays a property of
the port as follows.
Port name. Name of the port. Edit this field to change the port name.
Data type. Lists the data type of signals output by the port. Click the adjacent
button to display a list of supported data types. To change the port’s data type,
select a new type from the list.
Dimensions. Lists the number of dimensions of signals output by the port. To
display a list of supported dimensions, click the adjacent button. To change the
port’s dimensionality, select a new value from the list. (Simulink signals can
have at most two dimensions).
Row. Specifies the size of the output signal’s first (or only) dimension.
Column. Specifies the size of the output signal’s second dimension (only if the
output port accepts 2-D signals).
Complexity. Specifies whether the port outputs real or complex-valued signals.
Building S-Functions Automatically
Frame. Specifies whether this port accepts frame-based signals generated by
the Digital and Signal Processing Blockset and Communications Blockset. See
the documentation for these blocksets for more information.
Parameters Pane
The Parameters pane allows you to inspect and modify the properties of the
S-function’s parameters.
The pane comprises an editable table that lists the properties of the
S-function’s parameters . Each row of the table corresponds to a port. The order
in which the parameters appear corresponds to the order in which the user
must specify them. Each entry in the row displays a property of the parmeter
as follows.
Parameter name. Name of the parameter. Edit this field to change the name.
Data type. Lists the data type of the parameter. Click the adjacent button to
display a list of supported data types. To change the parameter’s data type,
select a new type from the list.
Complexity. Specifies whether the parameter has real or complex values.
Libraries Pane
The Libraries pane allows you to specify the location of external code files
referenced by custom code that you enter in other panes of the S-Function
Builder dialog box.
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3 Writing S-Functions in C
3-14
The Libraries pane includes the following fields.
Library/Object/Source files. External library, object code, and source files
referenced by custom code that you enter elsewhere on the S-Function Builder
dialog box. List each file on a separate line. If the file resides in the current
directory, you need specify only the file’s name. If the file resides in another
directory, you must specify the full path of the file.
Includes. Header files containing declarations of functions, variables, and
macros referenced by custom code that you enter elsewhere on the S-Function
Builder dialog box. Specify each file on a separate line as #include statements.
Use brackets to enclose the names of standard C header files (e.g., #include
<math.h>). Use quotation marks to enclose names of custom header files (e.g.,
#include "myutils.h"). If your S-function uses custom include files that do
not reside in the current directory, you must set the S-Function Builder’s
include path to the directories containing the include files (see “Setting the
Include Path” on page 3-23).
External function declarations. Declarations of external functions not declared in
the header files listed in the Includes field. Put each declaration on a separate
line. The S-Function Builder includes the specified declarations in the
S-function source file that it generates. This allows S-function code that
computes the S-function’s states or output to invoke the external functions.
Building S-Functions Automatically
Outputs Pane
Use the Outputs pane to enter code that computes the outputs of the
S-function at each simulation time step.
The Outputs pane contains the following fields.
Code for the mdlOutputs function. Code that computes the output of the S-function
at each simulation time step (or sample time hit in the case of a discrete
S-function). When generating the source code for the S-function, the
S-Function Builder inserts the code in this field in a wrapper function of the
form
void sfun_Outputs_wrapper(const real_T *u,
real_T *y,
const real_T *xD, /* optional */
const real_T *xC, /* optional */
const real_T *param0, /* optional */
int_T p_width0 /* optional */
real_T *param1 /* optional */
int_t p_width1 /* optional */
int_T y_width, /* optional */
int_T u_width) /* optional */
{
/* Your code inserted here */
3-15
}
3 Writing S-Functions in C
3-16
where sfun is the name of the S-function. The S-Function Builder inserts a call
to this wrapper function in the mdlOutputs callback method that it generates
for your S-function. Simulink invokes the mdlOutputs method at each
simulation time step (or sample time step in the case of a discrete S-function)
to compute the S-function’s output. The S-function’s mdlOutputs method in
turn invokes the wrapper function containing your output code. Your output
code then actually computes and returns the S-function’s output.
The mdlOutputs method passes some or all of the following arguments to the
outputs wrapper function.
Argument Description
u Pointer to an array containing the inputs to the S-function.
The width of the array is the same as the input width you
specified on the Initialization pane. If you specified -1 as
the input width, the width of the array is specified by the
wrapper function’s u_width argument (see below).
y Pointer to an array containing the output of the
S-function.The width of the array is the same as the output
width you specified on the Initialization pane. If you
specified -1 as the output width, the width of the array is
specified by the wrapper function’s y_width argument (see
below). Use this array to pass the outputs that your code
computes back to Simulink.
xD Pointer to an array containing the discrete states of the
S-function. This argument appears only if you specified
discrete states on the Initialization pane. At the first
simulation time step, the discrete states have the initial
values that you specified on the Initialization pane. At
subsequent sample-time steps, the states are obtained from
the values that the S-function computes at the preceding
time step (see “Discrete Update Pane” on page 3-21 for
more information).
Building S-Functions Automatically
These arguments permit you to compute the output of the block as a function
of its inputs and, optionally, its states and parameters. The code that you enter
in this field can invoke external functions declared in the header files or
external declarations on the Libraries pane. This allows you to use existing
code to compute the outputs of the S-function.
xC Pointer to an array containing the continuous states of the
S-function. This argument appears only if you specified
continuous states on the Initialization pane. At the first
simulation time step, the continuous states have the initial
values that you specified on the Initialization pane. At
subsequent time steps, the states are obtained by
numerically integrating the derivatives of the states at the
preceding time step (see “Continuous Derivatives Pane” on
page 3-19 for more information).
param0,
p_width0,
param1,
p_width1, ...
paramN,
p_widthN
param0, param1, paramN are pointers to arrays containing
the S-function’s parameters, where N is the number of
parameters specified on the Initialization pane. p_width0,
p_width1, p_widthN are the widths of the parameter
arrays. If a parameter is a matrix, the width equals the
product of the dimensions of the arrays. For example, the
width of a a 3-by-2 matrix parameter is 6. These arguments
appear only if you specify parameters on the Initialization
pane.
y_width Width of the array containing the S-function’s outputs.
This argument appears in the generated code only if you
specified -1 as the width of the S-function’s output. If the
output is a matrix, y_width is the product of the
dimensions of the matrix.
u_width Width of the array containing the S-function’s inputs. This
argument appears in the generated code only if you
specified -1 as the width of the S-function’s input. If the
input is a matrix, u_width is the product of the dimensions
of the matrix.
Argument Description
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3 Writing S-Functions in C
3-18
Inputs are needed in the output function. Selected if the current values of the
S-function’s inputs are used to compute its outputs. Simulink uses this
information to detect algebraic loops created by directly or indirectly
connecting the S-function’s output to its input.
Building S-Functions Automatically
Continuous Derivatives Pane
If the S-function has continuous states, use the Continuous Derivatives pane
to enter code required to compute the state derivatives.
Enter code to compute the derivatives of the S-function’s continuous states in
the Code for the mdlDerivatives function field on this pane. When
generating code, the S-Function Builder takes the code in this pane and inserts
it in a wrapper function of the form
void sfun_Derivatives_wrapper(const real_T *u,
const real_T *y,
real_T *dx,
real_T *xC,
const real_T *param0, /* optional */
int_T p_width0, /* optional */
real_T *param1,/* optional */
int_T p_width1, /* optional */
int_T y_width, /* optional */
int_T u_width) /* optional */
{
/* Your code inserted here. */
}
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3 Writing S-Functions in C
3-20
where sfun is the name of the S-function. The S-Function Builder inserts a call
to this wrapper function in the mdlDerivatives callback method that it
generates for the S-function. Simulink calls the mdlDerivatives method at the
end of each time step to obtain the derivatives of the S-function’s continuous
states (see “How Simulink Interacts with C S-Functions” on page 3-35).
Simulink’s solver numerically integrates the derivatives to determine the
continuous states at the next time step. At the next time step, Simulink passes
the updated states back to the S-function’s mdlOutputs method (see “Outputs
Pane” on page 3-15).
The generated S-function’s mdlDerivatives callback method passes the
following arguments to the derivatives wrapper function:
u
y
dx
xC
param0, p_width0, param1, p_width1, ... paramN, p_widthN
y_width
x-width
The dx argument is a pointer to an array whose width is the same as the
number of continuous derivatives specified on the Initialization pane. Your
code should use this array to return the values of the derivatives that it
computes. See “mdlOutputs” on page 3-28 for the meanings and usage of the
other arguments. The arguments allow your code to compute derivatives as a
function of the S-function’s inputs, outputs, and, optionally, parameters. Your
code can invoke external functions declared on the Libraries pane.
Building S-Functions Automatically
Discrete Update Pane
If the S-function has discrete states, use the Discrete Update pane to enter
code that computes at the current time step the values of the discrete states at
the next time step.
Enter code to compute the values of the S-function’s discrete states in the Code
for the mdlUpdate function field on this pane. When generating code, the
S-Function Builder takes the code in this pane and inserts it in a wrapper
function of the form
void sfun_Update_wrapper(const real_T *u,
const real_T *y,
real_T *xD,
const real_T *param0, /* optional */
int_T p_width0, /* optional */
real_T *param1,/* optional */
int_T p_width1, /* optional */
int_T y_width, /* optional */
int_T u_width) /* optional */
{
/* Your code inserted here. */
}
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3 Writing S-Functions in C
3-22
where sfun is the name of the S-function. The S-Function Builder inserts a call
to this wrapper function in the mdlUpdate callback method that it generates for
the S-function. Simulink calls the mdlUpdate method at the end of each time
step to obtain the values of the S-function’s discrete states at the next time step
(see “How Simulink Interacts with C S-Functions” on page 3-35). At the next
time step, Simulink passes the updated states back to the S-function’s
mdlOutputs method (see “Outputs Pane” on page 3-15).
The generated S-function’s mdlUpdates callback method passes the following
arguments to the updates wrapper function:
u
y
xD
param0, p_width0, param1, p_width1, ... paramN, p_widthN
y_width
x-width
See “mdlOutputs” on page 3-28 for the meanings and usage of these
arguments. Your code should use the xD (discrete states) variable to return the
values of the derivatives that it computes. The arguments allow your code to
compute the discrete states as functions of the S-function’s inputs, outputs,
and, optionally, parameters. Your code can invoke external functions declared
on the Libraries pane.
Building S-Functions Automatically
Build Info Pane
Use the Build Info pane to specify options for building the S-function MEX file.
This pane contains the following fields.
Compilation diagnostics. Display diagnostic messages issued by the S-Function
Builder when building the S-function.
Show compile steps. Log each build step in the Compilation diagnostics field.
Create a debuggable MEX-file. Include debug information in the generated
MEX-file.
Generate wrapper TLC. Generate a TCL file. You do not need to generate a TLC
file if you do not expect the S-function ever to run in accelerated mode or be
used in a model from which RTW generates code.
Save code only. Do not build a MEX file from the generated source code.
Setting the Include Path
The S-Function Builder searches for custom header files in the directories
specified by the MATLAB application data named
SfunctionBuilderIncludePath. This data is associated with the model in
which you create the S-Function Builder block. If your S-function uses custom
header files and the custom header files do not reside in the current directory
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3 Writing S-Functions in C
3-24
(i.e., the directory containing the generated S-function), you must update
SfunctionBuilderIncludePath to specify the locations of the directories
containing the header files. SfunctionBuilderIncludePath is a three-element
cell array that allows you to specify as many as three include directories. For
example, the following MATLAB commands set
SfunctionBuilderIncludePath to the paths of two include directories.
incPath = getappdata(0,'SfunctionBuilderIncludePath');
incPath{1} = '/home/jones/include';
incPath{2} = getenv('PROJECT_INCLUDE_DIR')
setappdata(0,'SfunctionBuilderIncludePath',incPath)
Example of a Basic C MEX S-Function
Example of a Basic C MEX S-Function
This section presents an example of a C MEX S-function that you can use as a
model for creating simple C S-functions. The example is the timestwo
S-function example that comes with Simulink (see
matlabroot/simulink/src/timestwo.c). This S-function outputs twice its
input.
The following model uses the timestwo S-function to double the amplitude of a
sine wave and plot it in a scope.
The block dialog for the S-function specifies timestwo as the S-function name;
the parameters field is empty.
The timestwo S-function contains the S-function callback methods shown in
this figure.
Start of simulation
mdlInitializeSizes
mdlInitializeSampleTimes
mdlOutputs
mdlTerminate
Simulation
loop
Initialization
3-25
3 Writing S-Functions in C
3-26
The contents of timestwo.c are shown below.
#define S_FUNCTION_NAME timestwo
#define S_FUNCTION_LEVEL 2
#include “simstruc.h”
static void mdlInitializeSizes(SimStruct *S)
{
ssSetNumSFcnParams(S, 0);
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
return; /* Parameter mismatch will be reported by Simulink */
}
if (!ssSetNumInputPorts(S, 1)) return;
ssSetInputPortWidth(S, 0, DYNAMICALLY_SIZED);
ssSetInputPortDirectFeedThrough(S, 0, 1);
if (!ssSetNumOutputPorts(S,1)) return;
ssSetOutputPortWidth(S, 0, DYNAMICALLY_SIZED);
ssSetNumSampleTimes(S, 1);
/* Take care when specifying exception free code - see sfuntmpl.doc */
ssSetOptions(S, SS_OPTION_EXCEPTION_FREE_CODE);
}
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, INHERITED_SAMPLE_TIME);
ssSetOffsetTime(S, 0, 0.0);
}
static void mdlOutputs(SimStruct *S, int_T tid)
{
int_T i;
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
real_T *y = ssGetOutputPortRealSignal(S,0);
int_T width = ssGetOutputPortWidth(S,0);
for (i=0; i<width; i++) {
*y++ = 2.0 *(*uPtrs[i]);
}
}
static void mdlTerminate(SimStruct *S){}
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include “simulink.c” /* MEX-file interface mechanism */
#else
#include “cg_sfun.h” /* Code generation registration function */
#endif
Example of a Basic C MEX S-Function
This example has three parts:
Defines and includes
Callback implementations
Simulink (or Real-Time Workshop) interface
The following sections explain each of these parts.
Defines and Includes
The example starts with the following defines.
#define S_FUNCTION_NAME timestwo
#define S_FUNCTION_LEVEL 2
The first specifies the name of the S-function (timestwo). The second specifies
that the S-function is in the level 2 format (for more information about level 1
and level 2 S-functions, see “Converting Level 1 C MEX S-Functions to Level
2” on page 3-44).
After defining these two items, the example includes simstruc.h, which is a
header file that gives access to the SimStruct data structure and the MATLAB
Application Program Interface (API) functions.
#define S_FUNCTION_NAME timestwo
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
The simstruc.h file defines a a data structure, called the SimStruct, that
Simulink uses to maintain information about the S-function. The simstruc.h
file also defines macros that enable your MEX-file to set values in and get
values (such as the input and output signal to the block) from the SimStruct
(see Chapter 10, “SimStruct Functions”).
Callback Implementations
The next part of the timestwo S-function contains implementations of callback
methods required by Simulink.
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3 Writing S-Functions in C
3-28
mdlInitializeSizes
Simulink calls mdlInitializeSizes to inquire about the number of input and
output ports, sizes of the ports, and any other objects (such as the number of
states) needed by the S-function.
The timestwo implementation of mdlInitializeSizes specifies the following
size information:
Zero parameters
This means that the S-function parameters field of the S-functions’s dialog
box must be empty. If it contains any parameters, Simulink reports a
parameter mismatch.
One input port and one output port
The widths of the input and output ports are dynamically sized. This tells
Simulink to multiply each element of the input signal to the S-function by 2
and to place the result in the output signal. Note that the default handling
for dynamically sized S-functions for this case (one input and one output) is
that the input and output widths are equal.
One sample time
The timestwo example specifies the actual value of the sample time in the
mdlInitializeSampleTimes routine.
The code is exception free.
Specifying exception-free code speeds up execution of your S-function. You
must take care when specifying this option. In general, if your S-function
isn’t interacting with MATLAB, it is safe to specify this option. For more
details, see “How Simulink Interacts with C S-Functions” on page 3-35.
mdlInitializeSampleTimes
Simulink calls mdlInitializeSampleTimes to set the sample times of the
S-function. A timestwo block executes whenever the driving block executes.
Therefore, it has a single inherited sample time, SAMPLE_TIME_INHERITED.
mdlOutputs
Simulink calls mdlOutputs at each time step to calculate a block’s outputs. The
timestwo implementation of mdlOutputs takes the input, multiplies it by 2,
and writes the answer to the output.
Example of a Basic C MEX S-Function
The timestwo mdlOutputs method uses a SimStruct macro,
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
to access the input signal. The macro returns a vector of pointers, which you
must access using
*uPtrs[i]
For more details, see “Data View” on page 3-39.
The timestwo mdlOutputs method uses the macro
real_T *y = ssGetOutputPortRealSignal(S,0);
to access the output signal. This macro returns a pointer to an array containing
the block’s outputs.
The S-function uses
int_T width = ssGetOutputPortWidth(S,0);
to get the width of the signal passing through the block. Finally, the S-function
loops over the inputs to compute the outputs.
mdlTerminate
Perform tasks at the end of the simulation. This is a mandatory S-function
routine. However, the timestwo S-function doesn’t need to perform any
termination actions, so this routine is empty.
Simulink/Real-Time Workshop Interface
At the end of the S-function, specify code that attaches this example to either
Simulink or the Real-Time Workshop.
#ifdef MATLAB_MEX_FILE
#include "simulink.c"
#else
#include "cg_sfun.h"
#endif
3-29
3 Writing S-Functions in C
3-30
Building the Timestwo Example
To incorporate this S-function into Simulink, enter
mex timestwo.c
at the command line. The mex command compiles and links the timestwo.c file
to create a dynamically loadable executable for Simulink’s use.
The resulting executable is referred to as a MEX S-function, where MEX
stands for “MATLAB EXecutable.” The MEX-file extension varies from
platform to platform. For example, in Microsoft Windows, the MEX-file
extension is .dll.
Templates for C S-Functions
Templates for C S-Functions
Simulink provides skeleton implementations of C MEX S-functions, called
templates, intended to serve as starting points for creating your own
S-functions. The templates contain skeleton implementations of callback
methods with comments that explain their use. The template file,
sfuntmpl_basic.c, which can be found in the directory simulink/src below
the MATLAB root directory, contains commonly used S-function routines. A
template containing all available routines (as well as more comments) can be
found in sfuntmpl_doc.c in the same directory.
Note We recommend that you use the C MEX-file template when developing
MEX S-functions.
S-Function Source File Requirements
This section describes requirements that every S-function source file must
meet to compile correctly. The S-function templates meet these requirements.
Statements Required at the Top of S-Functions
For S-functions to operate properly, each source module of your S-function that
accesses the SimStruct must contain the following sequence of defines and
include
#define S_FUNCTION_NAME your_sfunction_name_here
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
where your_sfunction_name_here is the name of your S-function (i.e., what
you enter in the Simulink S-Function block dialog). These statements give you
access to the SimStruct data structure that contains pointers to the data used
by the simulation. The included code also defines the macros used to store and
retrieve data in the SimStruct, described in detail in “Converting Level 1 C
MEX S-Functions to Level 2” on page 3-44. In addition, the code specifies that
you are using the level 2 format of S-functions.
3-31
3 Writing S-Functions in C
3-32
Note All S-functions from Simulink 1.3 through 2.1 are considered to be level
1 S-functions. They are compatible with Simulink 3.0, but we recommend that
you write new S-functions in the level 2 format.
The following headers are included by
matlabroot/simulink/include/simstruc.h when compiling as a MEX-file.
When compiling your S-function for use with the Real-Time Workshop,
simstruc.h includes the following.
Statements Required at the Bottom of S-Functions
Include this trailer code at the end of your C MEX S-function main module
only.
#ifdef MATLAB_MEX_FILE /* Is this being compiled as MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
Table 3-1: Header Files Included by simstruc.h When Compiling as a MEX-File
Header File Description
matlabroot/extern/include/tmwtypes.h General data types, e.g.,
real_T
matlabroot/extern/include/mex.h MATLAB MEX-file API
routines
matlabroot/extern/include/matrix.h MATLAB MEX-file API
routines
Table 3-2: Header Files Included by simstruc.h When Used
by the Real-Time Workshop
Header File Description
matlabroot/extern/include/tmwtypes.h General types, e.g., real_T
matlabroot/rtw/c/libsrc/rt_matrx.h Macros for MATLAB API
routines
Templates for C S-Functions
#else
#include "cg_sfun.h" /* Code generation registration func */
#endif
These statements select the appropriate code for your particular application:
simulink.c is included if the file is being compiled into a MEX-file.
cg_sfun.h is included if the file is being used in conjunction with the
Real-Time Workshop to produce a stand-alone or real-time executable.
Note This trailer code must not be in the body of any S-function routine.
The SimStruct
The file matlabroot/simulink/include/simstruc.h is a C language header
file that defines the Simulink data structure and the SimStruct access macros.
It encapsulates all the data relating to the model or S-function, including block
parameters and outputs.
There is one SimStruct data structure allocated for the Simulink model. Each
S-function in the model has its own SimStruct associated with it. The
organization of these SimStructs is much like a directory tree. The SimStruct
associated with the model is the root SimStruct. The SimStructs associated
with the S-functions are the child SimStructs.
Note By convention, port indices begin at 0 and finish at the total number of
ports minus 1.
Simulink provides a set of macros that S-functions can use to access the fields
of the SimStruct. See Chapter 10, “SimStruct Functions,” for more
information.
3-33
3 Writing S-Functions in C
3-34
Compiling C S-Functions
S-functions can be compiled in one of three modes identified by the presence of
one of the following defines:
MATLAB_MEX_FILE — Indicates that the S-function is being built as a
MEX-file for use with Simulink.
RT — Indicates that the S-function is being built with the Real-Time
Workshop generated code for a real-time application using a fixed-step
solver.
NRT — Indicates that the S-function is being built with the Real-Time
Workshop generated code for a non-real-time application using a
variable-step solver.
How Simulink Interacts with C S-Functions
How Simulink Interacts with C S-Functions
It is helpful in writing C MEX-file S-functions to understand how Simulink
interacts with S-functions. This section examines the interaction from two
perspectives: a process perspective, i.e., at which points in a simulation
Simulink invokes the S-function, and a data perspective, i.e., how Simulink
and the S-function exchange information during a simulation.
Process View
The following figures show the order in which Simulink invokes an S-function’s
callback methods. Solid rectangles indicate callbacks that always occur during
model initialization and/or at every time step. Dotted rectangles indicate
callbacks that may occur during initialization and/or at some or all time steps
during the simulation loop. See the documentation for each callback method in
“S-Function Callback Methods” on page 9-1 to determine the exact
circumstances under which Simulink invokes the callback.
3-35
3 Writing S-Functions in C
3-36
mdlIntializeSizes
mdlSetInputPortFrameData
mdlSetInputPortWidth/mdlSetOutputPortWidth
mdlSetInputPortDimensionInfo/mdlSetOutputPortDimensionInfo
mdlSetInputPortSampleTime/mdlSetOutputPortSampleTime
mdlInitializeSampleTimes
mdlSetInputPortDataType/mdlSetOutputPortDatatype
mdlSetDefaultPortDataTypes
mdlSetInputPortComplexSignal/mdlSetOutputPortComplexSignal
mdlSetDefaultPortComplexSignals
mdlSetWorkWidths
mdlStart
mdlInitializeConditions
mdlOutputs
mdlProcessParameters
To simulation loop
mdlCheckParameters
Simulink Engine
Sets output of
Constant blocks
mdlStart optionally calls
mdlProcessParameters
Model Initialization
mdlCheckParameters
mdlCheckParameters
followed by
How Simulink Interacts with C S-Functions
mdlProcessParameters
mdlGetTimeOfNextVarHit
mdlInitalizeConditions
mdlOutputs
mdlZeroCrossings
mdlTerminate
mdlDerivatives
mdlOutputs
mdlDerivatives
mdlUpdate
mdlOutputs
Simulation Loop
Simu
li
nk Eng
i
n
e
ma
j
o
r t
i
m
e
s
t
e
p
mi
no
r t
i
m
e
s
t
e
p
m
d
l
C
he
ck
P
a
rame
t
e
rs
Initialize Model
End Simulation
Integration
Zero-crossing detection
Called when parameters
change
Called when parameters
change.
Called if sample time of
this S-function varies
Called if this S-function
has continuous states
Called if this S-function
detects zero crossings
3-37
3 Writing S-Functions in C
3-38
Calling Structure for the Real Time Workshop
When generating code, the Real-Time Workshop does not go through the entire
calling sequence outlined above. After initializing the model as outlined in the
preceding section, Simulink calls mdlRTW, an S-function routine unique to the
Real-Time Workshop, mdlTerminate, and exits.
For more information about the Real-Time Workshop and how it interacts with
S-functions, see the Real-Time Workshop User’s Guide and the Target
Language Compiler Reference Guide.
Alternate Calling Structure for External Mode
When you are running Simulink in external mode, the calling sequence for
S-function routines changes. This picture shows the correct sequence for
external mode.
Simulink calls mdlRTW once when it enters external mode and again each time
a parameter changes or when you select Update Diagram under your model’s
Edit menu.
Note Running Simulink in external mode requires the Real-Time Workshop.
For more information about external mode, see the Real-Time Workshop
User’s Guide.
mdlRTW Called only if no run-time parametersp. 9-19
mdlTerminate
p. 9-39
Model Initialization
mdlCheckParameters
p. 9-2
mdlProcessParameters p. 9-17
Exter
n
al mo
de
p
a
r
a
m
e
t
e
r ch
a
n
ge
l
o
op
How Simulink Interacts with C S-Functions
Data View
S-function blocks have input and output signals, parameters, and internal
states, plus other general work areas. In general, block inputs and outputs are
written to, and read from, a block I/O vector. Inputs can also come from
External inputs via the root inport blocks
Ground if the input signal is unconnected or grounded
Block outputs can also go to the external outputs via the root outport blocks. In
addition to input and output signals, S-functions can have
Continuous states
Discrete states
Other working areas such as real, integer or pointer work vectors
You can parameterize S-function blocks by passing parameters to them using
the S-function block dialog box.
The following figure shows the general mapping between these various types
of data.
Block
Block I/O
External
Outputs
(root
outport
External
Inputs
(root
inport
Ground
States
Work
Vectors,
RWork,
IWork,
PWork,
Parameters
blocks)
blocks)
...
DWork,
3-39
3 Writing S-Functions in C
3-40
An S-function’s mdlInitializeSizes routine sets the sizes of the various
signals and vectors. S-function methods called during the simulation loop can
determine the sizes and values of the signals.
An S-function method can access input signals in two ways:
Via pointers
Using contiguous inputs
Accessing Signals Using Pointers
During the simulation loop, accessing the input signals is performed using
InputRealPtrsType uPtrs =
ssGetInputPortRealSignalPtrs(S,portIndex)
This is an array of pointers, where portIndex starts at 0. There is one for each
input port. To access an element of this signal you must use
*uPtrs[element]
as described by this figure.
S-Function
Block
Input 1
Input 2
uPtrs0
..
.
...
Block I/O
Vector
InputRealPtrsType uPtrs0 = ssGetInputPortRealSignalPtrs(S,0)
To access Input 1:
uPtrs1
..
.
InputRealPtrsType uPtrs1 = ssGetInputPortRealSignalPtrs(S,1)
To access Input 2:
How Simulink Interacts with C S-Functions
Note that input array pointers can point at noncontiguous places in memory.
You can retrieve the output signal by using this code.
real_T *y = ssGetOutputPortSignal(S,outputPortIndex);
Accessing Contiguous Input Signals
An S-function’s mdlInitializeSizes method can specify that the elements of
its input signals must occupy contiguous areas of memory, using
ssSetInputPortRequiredContiguous. If the inputs are contiguous, other
methods can use ssGetInputPortSignal to access the inputs.
Accessing Input Signals of Individual Ports
This section describes how to access all input signals of a particular port and
write them to the output port. The preceding figure shows that the input array
of pointers can point to noncontiguous entries in the block I/O vector. The
output signals of a particular port form a contiguous vector. Therefore, the
correct way to access input elements and write them to the output elements
(assuming the input and output ports have equal widths) is to use this code.
int_T element;
int_T portWidth = ssGetInputPortWidth(S,inputPortIndex);
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,inputPortIndex);
real_T *y = ssGetOutputPortSignal(S,outputPortIdx);
for (element=0; element<portWidth; element++) {
y[element] = *uPtrs[element];
}
A common mistake is to try to access the input signals via pointer arithmetic.
For example, if you were to place
real_T *u = *uPtrs; /* Incorrect */
just below the initialization of uPtrs and replace the inner part of the above
loop with
*y++ = *u++; /* Incorrect */
the code compiles, but the MEX-file might crash Simulink. This is because it is
possible to access invalid memory (which depends on how you build your
model). When accessing the input signals incorrectly, a crash occurs when the
signals entering your S-function block are not contiguous. Noncontiguous
signal data occurs when signals pass through virtual connection blocks such as
3-41
the Mux or Selector blocks.
3 Writing S-Functions in C
3-42
To verify that you are correctly accessing wide input signals, pass a replicated
signal to each input port of your S-function. You do this by creating a Mux block
with the number of input ports equal to the width of the desired signal entering
your S-function. Then the driving source should be connected to each input port
as shown in this figure.
Source signal Mux S-function
Writing Callback Methods
Writing Callback Methods
Writing an S-function basically involves creating implementations of the
callback functions that Simulink invokes during a simulation. For guidelines
on implementing a particular callback, see the documentation for the callback
in Chapter 9, “S-Function Callback Methods.” For information on using
callbacks to implement specific block features, such as parameters or sample
times, see Chapter 7, “Implementing Block Features.”
3-43
3 Writing S-Functions in C
3-44
Converting Level 1 C MEX S-Functions to Level 2
Level 2 S-functions were introduced with Simulink 2.2. Level 1 S-functions
refer to S-functions that were written to work with Simulink 2.1 and previous
releases. Level 1 S-functions are compatible with Simulink 2.2 and subsequent
releases; you can use them in new models without making any code changes.
However, to take advantage of new features in S-functions, level 1 S-functions
must be updated to level 2 S-functions. Here are some guidelines:
Start by looking at simulink/src/sfunctmpl_doc.c. This template
S-function file concisely summarizes level 2 S-functions.
At the top of your S-function file, add this define:
#define S_FUNCTION_LEVEL 2
Update the contents of mdlInitializeSizes. In particular, add the following
error handling for the number of S-function parameters:
ssSetNumSFcnParams(S, NPARAMS); /*Number of expected parameters*/
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
/* Return if number of expected != number of actual parameters */
return;
}
Set up the inputs using:
if (!ssSetNumInputPorts(S, 1)) return; /*Number of input ports */
ssSetInputPortWidth(S, 0, width); /* Width of input
port one (index 0)*/
ssSetInputPortDirectFeedThrough(S, 0, 1); /* Direct feedthrough
or port one */
ssSetInputPortRequiredContiguous(S, 0);
Set up the outputs using:
if (!ssSetNumOutputPorts(S, 1)) return;
ssSetOutputPortWidth(S, 0, width); /* Width of output port
one (index 0) */
If your S-function has a nonempty mdlInitializeConditions, update it to
the following form:
#define MDL_INITIALIZE_CONDITIONS
static void mdlInitializeConditions(SimStruct *S)
{
}
Otherwise, delete the function.
- Access the continuous states using ssGetContStates. The ssGetX macro
has been removed.
- Access the discrete states using ssGetRealDiscStates(S). The ssGetX
macro has been removed.
Converting Level 1 C MEX S-Functions to Level 2
- For mixed continuous and discrete state S-functions, the state vector no
longer consists of the continuous states followed by the discrete states. The
states are saved in separate vectors and hence might not be contiguous in
memory.
The mdlOutputs prototype has changed from
static void mdlOutputs( real_T *y, const real_T *x,
const real_T *u, SimStruct *S, int_T tid)
to
static void mdlOutputs(SimStruct *S, int_T tid)
Since y, x, and u are not explicitly passed in to level-2 S-functions, you must
use
- ssGetInputPortSignal to access inputs
- ssGetOutputPortSignal to access the outputs
- ssGetContStates or ssGetRealDiscStates to access the states
The mdlUpdate function prototype has changed from
void mdlUpdate(real_T *x, real_T *u, Simstruct *S, int_T tid)
to
void mdlUpdate(SimStruct *S, int_T tid)
If your S-function has a nonempty mdlUpdate, update it to this form:
#define MDL_UPDATE
static void mdlUpdate(SimStruct *S, int_T tid)
{
}
Otherwise, delete the function.
If your S-function has a nonempty mdlDerivatives, update it to this form:
#define MDL_DERIVATIVES
static void mdlDerivatives(SimStruct *S, int_T tid)
{
}
Otherwise, delete the function.
Replace all obsolete SimStruct macros. See “Obsolete Macros” on page 3-46
3-45
for a complete list of obsolete macros.
3 Writing S-Functions in C
3-46
When converting level 1 S-functions to level 2 S-functions, you should build
your S-functions with full (i.e., highest) warning levels. For example, if you
have gcc on a UNIX system, use these options with the mex utility.
mex CC=gcc CFLAGS=-Wall sfcn.c
If your system has Lint, use this code.
lint -DMATLAB_MEX_FILE -I<matlabroot>/simulink/include
-Imatlabroot/extern/include sfcn.c
On a PC, to use the highest warning levels, you must create a project file
inside the integrated development environment (IDE) for the compiler you
are using. Within the project file, define MATLAB_MEX_FILE and add
matlabroot/simulink/include
matlabroot/extern/include
to the path (be sure to build with alignment set to 8).
Obsolete Macros
The following macros are obsolete. Each obsolete macro should be replaced
with the specified macro.
Obsolete Macro Replace With
ssGetU(S), ssGetUPtrs(S) ssGetInputPortSignalPtrs(S,port)
ssGetY(S) ssGetOutputPortRealSignal(S,port)
ssGetX(S) ssGetContStates(S), ssGetRealDiscStates(S)
ssGetStatus(S) Normally not used, but ssGetErrorStatus(S) is
available.
ssSetStatus(S,msg) ssSetErrorStatus(S,msg)
ssGetSizes(S) Specific call for the wanted item (i.e.,
ssGetNumContStates(S))
ssGetMinStepSize(S) No longer supported.
ssGetPresentTimeEvent(S,sti) ssGetTaskTime(S,sti)
Converting Level 1 C MEX S-Functions to Level 2
ssGetSampleTimeEvent(S,sti) ssGetSampleTime(S,sti)
ssSetSampleTimeEvent(S,t) ssSetSampleTime(S,sti,t)
ssGetOffsetTimeEvent(S,sti) ssGetOffsetTime(S,sti)
ssSetOffsetTimeEvent(S,sti,t) ssSetOffsetTime(S,sti,t)
ssIsSampleHitEvent(S,sti,tid) ssIsSampleHit(S,sti,tid)
ssGetNumInputArgs(S) ssGetNumSFcnParams(S)
ssSetNumInputArgs(S, numInputArgs) ssSetNumSFcnParams(S,numInputArgs)
ssGetNumArgs(S) ssGetSFcnParamsCount(S)
ssGetArg(S,argNum) ssGetSFcnParam(S,argNum)
ssGetNumInputs ssGetNumInputPorts(S) and
ssGetInputPortWidth(S,port)
ssSetNumInputs ssSetNumInputPorts(S,nInputPorts) and
ssSetInputPortWidth(S,port,val)
ssGetNumOutputs ssGetNumOutputPorts(S) and
ssGetOutputPortWidth(S,port)
ssSetNumOutputs ssSetNumOutputPorts(S,nOutputPorts) and
ssSetOutputPortWidth(S,port,val)
Obsolete Macro Replace With
3-47
3 Writing S-Functions in C
3-48
4
Creating C++ S-Functions
The procedure for creating C++ S-functions is nearly the same as that for creating C S-functions (see
Chapter 3, “Writing S-Functions in C”). The following sections explain the differences.
Source File Format (p. 4-2) Explains the differences between the source file structure
of a C++ S-function and a C S-function.
Making C++ Objects Persistent (p. 4-6) How to create C++ objects that persist across invocations
of the S-function.
Building C++ S-Functions (p. 4-7) How to build a C++ S-function.
4 Creating C++ S-Functions
4-2
Source File Format
The format of the C++ source for an S-function is nearly identical to that of the
source for an S-function written in C. The main difference is that you must tell
the C++ compiler to use C calling conventions when compiling the callback
methods. This is necessary because the Simulink simulation engine assumes
that callback methods obey C calling conventions.
To tell the compiler to use C calling conventions when compiling the callback
methods, wrap the C++ source for the S-function callback methods in an
extern "C" statement. The C++ version of the sfun_counter S-function
example (matlabroot/simulink/src/sfun_counter_cpp.cpp) illustrates
usage of the extern "C" directive to ensure that the compiler generates
Simulink-compatible callback methods:
/* File : sfun_counter_cpp.cpp
* Abstract:
*
* Example of an C++ S-function which stores an C++ object in
* the pointers vector PWork.
*
* Copyright 1990-2000 The MathWorks, Inc.
*
*/
#include "iostream.h"
class counter {
double x;
public:
counter() {
x = 0.0;
}
double output(void) {
x = x + 1.0;
return x;
}
};
#ifdef __cplusplus
extern "C" { // use the C fcn-call standard for all functions
#endif // defined within this scope
#define S_FUNCTION_LEVEL 2
#define S_FUNCTION_NAME sfun_counter_cpp
/*
* Need to include simstruc.h for the definition of the SimStruct and
* its associated macro definitions.
Source File Format
*/
#include "simstruc.h"
/*====================*
* S-function methods *
*====================*/
/* Function: mdlInitializeSizes ===============================================
* Abstract:
* The sizes information is used by Simulink to determine the S-function
* block's characteristics (number of inputs, outputs, states, etc.).
*/
static void mdlInitializeSizes(SimStruct *S)
{
/* See sfuntmpl_doc.c for more details on the macros below */
ssSetNumSFcnParams(S, 1); /* Number of expected parameters */
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
/* Return if number of expected != number of actual parameters */
return;
}
ssSetNumContStates(S, 0);
ssSetNumDiscStates(S, 0);
if (!ssSetNumInputPorts(S, 0)) return;
if (!ssSetNumOutputPorts(S, 1)) return;
ssSetOutputPortWidth(S, 0, 1);
ssSetNumSampleTimes(S, 1);
ssSetNumRWork(S, 0);
ssSetNumIWork(S, 0);
ssSetNumPWork(S, 1); // reserve element in the pointers vector
ssSetNumModes(S, 0); // to store a C++ object
ssSetNumNonsampledZCs(S, 0);
ssSetOptions(S, 0);
}
/* Function: mdlInitializeSampleTimes =========================================
* Abstract:
* This function is used to specify the sample time(s) for your
* S-function. You must register the same number of sample times as
* specified in ssSetNumSampleTimes.
*/
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, mxGetScalar(ssGetSFcnParam(S, 0)));
4-3
ssSetOffsetTime(S, 0, 0.0);
4 Creating C++ S-Functions
4-4
}
#define MDL_START /* Change to #undef to remove function */
#if defined(MDL_START)
/* Function: mdlStart =======================================================
* Abstract:
* This function is called once at start of model execution. If you
* have states that should be initialized once, this is the place
* to do it.
*/
static void mdlStart(SimStruct *S)
{
ssGetPWork(S)[0] = (void *) new counter; // store new C++ object in the
} // pointers vector
#endif /* MDL_START */
/* Function: mdlOutputs =======================================================
* Abstract:
* In this function, you compute the outputs of your S-function
* block. Generally outputs are placed in the output vector, ssGetY(S).
*/
static void mdlOutputs(SimStruct *S, int_T tid)
{
counter *c = (counter *) ssGetPWork(S)[0]; // retrieve C++ object from
real_T *y = ssGetOutputPortRealSignal(S,0); // the pointers vector and use
y[0] = c->output(); // member functions of the
} // object
/* Function: mdlTerminate =====================================================
* Abstract:
* In this function, you should perform any actions that are necessary
* at the termination of a simulation. For example, if memory was
* allocated in mdlStart, this is the place to free it.
*/
static void mdlTerminate(SimStruct *S)
{
counter *c = (counter *) ssGetPWork(S)[0]; // retrieve and destroy C++
delete c; // object in the termination
} // function
/*======================================================*
* See sfuntmpl_doc.c for the optional S-function methods *
*======================================================*/
/*=============================*
* Required S-function trailer *
*=============================*/
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration function */
#endif
Source File Format
#ifdef __cplusplus
} // end of extern "C" scope
#endif
4-5
4 Creating C++ S-Functions
4-6
Making C++ Objects Persistent
Your C++ callback methods might need to create persistent C++ objects, that
is, objects that continue to exist after the method exits. For example, a callback
method might need to access an object created during a previous invocation. Or
one callback method might need to access an object created by another callback
method. To create persistent C++ objects in your S-function:
1 Create a pointer work vector to hold pointers to the persistent object
between method invocations:
static void mdlInitializeSizes(SimStruct *S)
{
...
ssSetNumPWork(S, 1); // reserve element in the pointers vector
// to store a C++ object
...
}
2 Store a pointer to each object that you want to be persistent in the pointer
work vector:
static void mdlStart(SimStruct *S)
{
ssGetPWork(S)[0] = (void *) new counter; // store new C++ object in the
} // pointers vector
3 Retrieve the pointer in any subsequent method invocation to access the
object:
static void mdlOutputs(SimStruct *S, int_T tid)
{
counter *c = (counter *) ssGetPWork(S)[0]; // retrieve C++ object from
real_T *y = ssGetOutputPortRealSignal(S,0); // the pointers vector and use
y[0] = c->output(); // member functions of the
} // object
4 Destroy the objects when the simulation terminates:
static void mdlTerminate(SimStruct *S)
{
counter *c = (counter *) ssGetPWork(S)[0]; // retrieve and destroy C++
delete c; // object in the termination
} // function
Building C++ S-Functions
Building C++ S-Functions
Use the MATLAB mex command to build C++ S-functions exactly the way you
use it to build C S-functions. For example, to build the C++ version of the
sfun_counter example, enter
mex sfun_counter_cpp.cpp
at the MATLAB command line.
Note The extension of the source file for a C++ S-function must be .cpp to
ensure that the compiler treats the file’s contents as C++ code.
4-7
4 Creating C++ S-Functions
4-8
5
Creating Ada S-Functions
The following sections explain how to use the Ada programming language to create S-functions.
Introduction (p. 5-2) Overview of creating Ada S-functions.
Ada S-Function Source File Format
(p. 5-3)
Source code structure of an Ada S-function.
Writing Callback Methods in Ada
(p. 5-6)
How to use Ada to implement S-function callback
methods.
Building an Ada S-Function (p. 5-9) Compiling and linking an Ada S-function.
Example of an Ada S-Function (p. 5-10) An Ada version of the timestwo S-function example.
5 Creating Ada S-Functions
5-2
Introduction
Simulink allows you to use the Ada programming language to create
S-functions. As with S-functions coded in other programming languages,
Simulink interacts with an Ada S-function by invoking callback methods that
the S-function implements. Each method performs a predefined task, such as
computing block outputs, required to simulate the block whose functionality
the S-function defines. Creating an Ada S-function thus entails writing Ada
implementations of the callback methods required to simulate the S-function
and then compiling and linking the callbacks into a library that Simulink can
load and invoke during simulation The following sections explain how to
perform these tasks.
Ada S-Function Source File Format
Ada S-Function Source File Format
To create an Ada S-function, you must create an Ada package that implements
the callback methods required to simulate the S-function. The S-function
package comprises a specification and a body.
Ada S-Function Specification
The specification specifies the methods that the Ada S-function uses and
implements. The specification must specify that the Ada S-function uses the
Simulink package, which defines data types and functions that the S-function
can use to access the internal data structure (SimStruct) that Simulink uses to
store information about the S-function (see Chapter 10, “SimStruct
Functions”). The specification and body of the Simulink package reside in the
matlabroot/simulink/ada/interface/ directory.
The specification should also specify each callback method that the S-function
implements as an Ada procedure exported to C. The following is an example of
an Ada S-function specification that meets these requirements.
-- The Simulink API for Ada S-Function
with Simulink; use Simulink;
package Times_Two is
-- The S_FUNCTION_NAME has to be defined as a constant
-- string.
--
S_FUNCTION_NAME : constant String := "times_two";
-- Every S-Function is required to have the
-- "mdlInitializeSizes" method.
-- This method needs to be exported as shown below, with the
-- exported name being "mdlInitializeSizes".
--
procedure mdlInitializeSizes(S : in SimStruct);
pragma Export(C, mdlInitializeSizes, "mdlInitializeSizes");
procedure mdlOutputs(S : in SimStruct; TID : in Integer);
pragma Export(C, mdlOutputs, "mdlOutputs");
end Times_Two;
5-3
5 Creating Ada S-Functions
5-4
Ada S-Function Body
The Ada S-Function body provides the implementations of the S-function
callback methods, as illustrated in the following example.
with Simulink; use Simulink;
with Ada.Exceptions; use Ada.Exceptions;
package body Times_Two is
-- Function: mdlInitializeSizes ---------------------------------------------
-- Abstract:
-- Setup the input and output port attributes for this
-- S-Function.
--
procedure mdlInitializeSizes(S : in SimStruct) is
begin
-- Set the input port attributes
--
ssSetNumInputPorts( S, 1);
ssSetInputPortWidth( S, 0, DYNAMICALLY_SIZED);
ssSetInputPortDataType( S, 0, SS_DOUBLE);
ssSetInputPortDirectFeedThrough(S, 0, TRUE);
ssSetInputPortOverWritable( S, 0, FALSE);
ssSetInputPortOptimizationLevel(S, 0, 3);
-- Set the output port attributes
--
ssSetNumOutputPorts( S, 1);
ssSetOutputPortWidth( S, 0, DYNAMICALLY_SIZED);
ssSetOutputPortDataType( S, 0, SS_DOUBLE);
ssSetOutputPortOptimizationLevel(S, 0, 3);
-- Set the block sample time.
ssSetSampleTime( S, INHERITED_SAMPLE_TIME);
exception
when E : others =>
if ssGetErrorStatus(S) = "" then
ssSetErrorStatus(S,
"Exception occured in mdlInitializeSizes. " &
"Name: " & Exception_Name(E) & ", " &
"Message: " & Exception_Message(E) &
" and " & "Information: " &
Exception_Information(E));
end if;
end mdlInitializeSizes;
-- Function: mdlOutputs -----------------------------------------------------
-- Abstract:
Ada S-Function Source File Format
-- Compute the S-Function's output,
-- given its input: y = 2 * u
--
procedure mdlOutputs(S : in SimStruct; TID : in Integer) is
uWidth : Integer := ssGetInputPortWidth(S,0);
U : array(0 .. uWidth-1) of Real_T;
for U'Address use ssGetInputPortSignalAddress(S,0);
yWidth : Integer := ssGetOutputPortWidth(S,0);
Y : array(0 .. yWidth-1) of Real_T;
for Y'Address use ssGetOutputPortSignalAddress(S,0);
begin
if uWidth = 1 then
for Idx in 0 .. yWidth-1 loop
Y(Idx) := 2.0 * U(0);
end loop;
else
for Idx in 0 .. yWidth-1 loop
Y(Idx) := 2.0 * U(Idx);
end loop;
end if;
exception
when E : others =>
if ssGetErrorStatus(S) = "" then
ssSetErrorStatus(S,
"Exception occured in mdlOutputs. " &
"Name: " & Exception_Name(E) & ", " &
"Message: " & Exception_Message(E) & " and " &
"Information: " & Exception_Information(E));
end if;
end mdlOutputs;
end Times_Two;
5-5
5 Creating Ada S-Functions
5-6
Writing Callback Methods in Ada
Simulink interacts with an Ada S-function by invoking callback methods that
the S-function implements. This section specifies the callback methods that an
Ada S-function can implement and provides guidelines for implementing them.
Callbacks Invoked by Simulink
The following diagram shows the callback methods that Simulink invokes
when interacting with an Ada S-function during a simulation and the order in
which Simulink invokes them.
Writing Callback Methods in Ada
Note When interacting with Ada S-functions, Simulink invokes only a subset
of the callback methods that it invokes for C S-functions. The “Languages
Supported” section of the reference page for each callback method specifies
whether Simulink invokes that callback when interacting with an Ada
S-function.
Implementing Callbacks
Simulink defines in a general way the task of each callback. The S-function is
free to perform the task according to the functionality it implements. For
example, Simulink specifies that the S-function’s mdlOutputs method must
compute that block’s outputs at the current simulation time. It does not specify
what those outputs must be. This callback-based API allows you to create
S-functions, and hence custom blocks, that meet your requirements.
Chapter 9, “S-Function Callback Methods,” explains the purpose of each
callback and provides guidelines for implementing them. Chapter 3, “Writing
S-Functions in C,” provides information on using these callbacks to implement
specific S-function features, such as the ability to handle multiple signal data
types.
Omitting Optional Callback Methods
The method mdlInitializeSizes is the only callback that an Ada S-function
must implement. The source for your Ada S-function needs to include
implementations only for callbacks that it must handle. If the source for your
S-function does not include an implementation for a particular callback, the
mex tool that builds the S-function (see “Building an Ada S-Function” on
page 5-9) provides a stub implementation.
SimStruct Functions
Simulink provides a set of functions that enable an Ada S-function to access the
internal data structure (SimStruct) that Simulink maintains for the
S-function. These functions consist of Ada wrappers around the SimStruct
macros used to access the SimStruct from a C S-function (see Chapter 10,
“SimStruct Functions”). Simulink provides Ada wrappers for a substantial
5-7
5 Creating Ada S-Functions
5-8
subset of the SimStruct macros. The “Languages Supported” section of the
reference page for a macro specifies whether it has an Ada wrapper.
Building an Ada S-Function
Building an Ada S-Function
To use your Ada S-function with Simulink, you must build a MATLAB
executable (MEX) file from the Ada source code for the S-function. Use the
MATLAB mex command to perform this step.
The mex syntax for building an Ada S-function MEX file is
mex [-v] [-g] -ada SFCN.ads
where SFCN.ads is the name of the S-function’s package specification.
For example, to build the timestwo S-function example that comes with
Simulink, enter the command
mex -ada timestwo.ads
Ada Compiler Requirements
To build a MEX file from Ada source code, using the mex tool, you must have
previously installed a copy of version 3.12 (or higher) of the GNAT Ada95
compiler on your system. You can obtain the latest Solaris, Windows, and
GNU-Linux versions of the compiler at the GNAT ftp site
(ftp://cs.nyu.edu/pub/gnat). Make sure that the compiler executable is in
MATLAB’s command path so that the mex tool can find it.
The GNAT Ada95 compiler package used to include gnatdll.exe, a tool for
building DLLs on Windows. This tool, which is required to build Ada MEX files
on Windows, now comes as part of a separate gnatwin package containing
Windows-specific files. If you want to build Ada S-functions on a Windows
system, you must download and install the gnatwin package as well as the
GNAT Ada95 compiler.
5-9
5 Creating Ada S-Functions
5-10
Example of an Ada S-Function
This section presents an example of a basic Ada S-function that you can use as
a model when creating your own Ada S-functions. The example is the timestwo
S-function example that comes with Simulink (see
matlabroot/simulink/ada/examples/timestwo.ads and
matlabroot/simulink/ada/examples/timestwo.adb). This S-function outputs
twice its input.
The following model uses the timestwo S-function to double the amplitude of a
sine wave and plot it in a scope.
The block dialog for the S-function specifies timestwo as the S-function name;
the parameters field is empty.
The timestwo S-function contains the S-function callback methods shown in
this figure.
Start of simulation
mdlInitializeSizes
mdlInitializeSampleTimes
mdlOutputs
Simulation
loop
Initialization
end of simulation
Example of an Ada S-Function
The source code for the timestwo S-function comprises two parts:
Package specification
Package body
The following sections explain each of these parts.
Timestwo Package Specification
The timestwo package specification, timestwo.ads, contains the following
code.
-- The Simulink API for Ada S-Function
with Simulink; use Simulink;
package Times_Two is
-- The S_FUNCTION_NAME has to be defined as a constant string. Note that
-- the name of the S-Function (ada_times_two) is different from the name
-- of this package (times_two). We do this so that it is easy to identify
-- this example S-Function in the MATLAB workspace. Normally you would use
-- the same name for S_FUNCTION_NAME and the package.
--
S_FUNCTION_NAME : constant String := "ada_times_two";
-- Every S-Function is required to have the "mdlInitializeSizes" method.
-- This method needs to be exported as shown below, with the exported name
-- being "mdlInitializeSizes".
--
procedure mdlInitializeSizes(S : in SimStruct);
pragma Export(C, mdlInitializeSizes, "mdlInitializeSizes");
procedure mdlOutputs(S : in SimStruct; TID : in Integer);
pragma Export(C, mdlOutputs, "mdlOutputs");
end Times_Two;
The package specification begins by specifying that the S-function uses the
Simulink package.
with Simulink; use Simulink;
The Simulink package defines Ada procedures for accessing the internal data
structure (SimStruct) that Simulink maintains for each S-function (see
Chapter 10, “SimStruct Functions”).
5-11
5 Creating Ada S-Functions
5-12
Next the specification specifies the name of the S-function.
S_FUNCTION_NAME : constant String := "ada_times_two";
The name ada_times_two serves to distinguish the MEX-file generated from
Ada source from those generated from the timestwo source coded in other
languages.
Finally the specification specifies the callback methods implemented by the
timestwo S-function.
procedure mdlInitializeSizes(S : in SimStruct);
pragma Export(C, mdlInitializeSizes, "mdlInitializeSizes");
procedure mdlOutputs(S : in SimStruct; TID : in Integer);
pragma Export(C, mdlOutputs, "mdlOutputs");
The specification specifies that the Ada compiler should compile each method
as a C-callable function. This is because the Simulink engine assumes that
callback methods are C functions.
Note When building an Ada S-function, MATLAB’s mex tool uses the package
specification to determine the callbacks that the S-function does not
implement. It then generates stubs for the nonimplemented methods.
Timestwo Package Body
The timestwo package body, timestwo.adb, contains
with Simulink; use Simulink;
with Ada.Exceptions; use Ada.Exceptions;
package body Times_Two is
-- Function: mdlInitializeSizes ---------------------------------------------
-- Abstract:
-- Setup the input and output port attrubouts for this S-Function.
--
procedure mdlInitializeSizes(S : in SimStruct) is
begin
-- Set the input port attributes
--
ssSetNumInputPorts( S, 1);
Example of an Ada S-Function
ssSetInputPortWidth( S, 0, DYNAMICALLY_SIZED);
ssSetInputPortDataType( S, 0, SS_DOUBLE);
ssSetInputPortDirectFeedThrough(S, 0, TRUE);
ssSetInputPortOverWritable( S, 0, FALSE);
ssSetInputPortOptimizationLevel(S, 0, 3);
-- Set the output port attributes
--
ssSetNumOutputPorts( S, 1);
ssSetOutputPortWidth( S, 0, DYNAMICALLY_SIZED);
ssSetOutputPortDataType( S, 0, SS_DOUBLE);
ssSetOutputPortOptimizationLevel(S, 0, 3);
-- Set the block sample time.
ssSetSampleTime( S, INHERITED_SAMPLE_TIME);
exception
when E : others =>
if ssGetErrorStatus(S) = "" then
ssSetErrorStatus(S,
"Exception occured in mdlInitializeSizes. " &
"Name: " & Exception_Name(E) & ", " &
"Message: " & Exception_Message(E) & " and " &
"Information: " & Exception_Information(E));
end if;
end mdlInitializeSizes;
-- Function: mdlOutputs -----------------------------------------------------
-- Abstract:
-- Compute the S-Function's output, given its input: y = 2 * u
--
procedure mdlOutputs(S : in SimStruct; TID : in Integer) is
uWidth : Integer := ssGetInputPortWidth(S,0);
U : array(0 .. uWidth-1) of Real_T;
for U'Address use ssGetInputPortSignalAddress(S,0);
yWidth : Integer := ssGetOutputPortWidth(S,0);
Y : array(0 .. yWidth-1) of Real_T;
for Y'Address use ssGetOutputPortSignalAddress(S,0);
begin
if uWidth = 1 then
for Idx in 0 .. yWidth-1 loop
Y(Idx) := 2.0 * U(0);
end loop;
else
for Idx in 0 .. yWidth-1 loop
Y(Idx) := 2.0 * U(Idx);
end loop;
end if;
5-13
5 Creating Ada S-Functions
5-14
exception
when E : others =>
if ssGetErrorStatus(S) = "" then
ssSetErrorStatus(S,
"Exception occured in mdlOutputs. " &
"Name: " & Exception_Name(E) & ", " &
"Message: " & Exception_Message(E) & " and " &
"Information: " & Exception_Information(E));
end if;
end mdlOutputs;
end Times_Two;
The package body contains implementations of the callback methods needed to
implement the timestwo example.
mdlInitializeSizes
Simulink calls mdlInitializeSizes to inquire about the number of input and
output ports, the sizes of the ports, and any other objects (such as the number
of states) needed by the S-function.
The timestwo implementation of mdlInitializeSizes uses SimStruct
functions defined in the Simulink package to specify the following size
information:
One input port and one output port
The widths of the input and output port are dynamically sized. This tells
Simulink to multiply each element of the input signal to the S-function by 2
and to place the result in the output signal. Note that the default handling
for dynamically sized S-functions for this case (one input and one output) is
that the input and output widths are equal.
One sample time
Finally the method provides an exception handler to handle any errors that
occur in invoking the SimStruct functions.
mdlOutputs
Simulink calls mdlOutputs at each time step to calculate a block’s outputs. The
timestwo implementation of mdlOutputs takes the input, multiplies it by 2,
and writes the answer to the output.
Example of an Ada S-Function
The timestwo implementation of the mdlOutputs method uses the SimStruct
functions ssGetInputPortWidth and ssGetInputPortSignalAddress to access
the input signal.
uWidth : Integer := ssGetInputPortWidth(S,0);
U : array(0 .. uWidth-1) of Real_T;
for U'Address use ssGetInputPortSignalAddress(S,0);
Similarly, the mdlOutputs method uses the functions ssGetOutputPortWidth
and ssGetOutputPortSignalAddress to access the output signal.
yWidth : Integer := ssGetOutputPortWidth(S,0);
Y : array(0 .. yWidth-1) of Real_T;
for Y'Address use ssGetOutputPortSignalAddress(S,0);
Finally the method loops over the inputs to compute the outputs.
Building the Timestwo Example
To build this S-function into Simulink, enter
mex -ada timestwo.abs
at the command line.
5-15
5 Creating Ada S-Functions
5-16
6
Creating Fortran
S-Functions
The following sections explain how to use the Fortran programming language to create S-functions.
Introduction (p. 6-2) Overview of approaches to writing Fortran S-functions.
Creating Level 1 Fortran S-Functions
(p. 6-3)
Describes a purely Fortran approach to creating an
S-function.
Creating Level 2 Fortran S-Functions
(p. 6-7)
Describes a hybrid C/Fortran approach to writing an
S-function that enables creation of more capable blocks.
Porting Legacy Code (p. 6-14) How to wrap an S-function around existing Fortran code.
6 Creating Fortran S-Functions
6-2
Introduction
There are two main strategies to executing Fortran code from Simulink. One is
from a level 1 Fortran-MEX (F-MEX) S-function, the other is from a level 2
gateway S-function written in C. Each has its advantages and both can be
incorporated into code generated by the Real-Time Workshop.
Level 1 Versus Level 2 S-Functions
The original S-function interface was called the Level 1 API. As the capabilities
of Simulink grew, the S-function API was rearchitected into the more
extensible Level 2 API. This allows S-functions to have all the capabilities of a
full Simulink model (except automatic algebraic loop identification and
solving) and to grow as Simulink grows.
Creating Level 1 Fortran S-Functions
Creating Level 1 Fortran S-Functions
The Fortran MEX Template File
A template file for Fortran MEX S-functions is located at
matlabroot/simulink/src/sfuntmpl_fortran.for. The template file
compiles as is and copies the input to the output.
To use the template to create a new Fortran S-function:
1 Create a copy under another filename.
2 Edit the copy to perform the operations you need.
3 Compile the edited file into a MEX file, using the mex command.
4 Include the MEX file in your model, using the S-Function block.
Example
The example file, matlabroot/simulink/src/sfun_timestwo_for.for,
implements an S-function that multiplies its input by 2.
C
C File: SFUN_TIMESTWO_FOR.F
C
C Abstract:
C A sample Level 1 FORTRAN representation of a
C timestwo S-function.
C
C The basic mex command for this example is:
C
C >> mex sfun_timestwo_for.for simulink.for
C
C Copyright 1990-2000 The MathWorks, Inc.
C
C
C
C=====================================================
C Function: SIZES
C
C Abstract:
C Set the size vector.
C
C SIZES returns a vector which determines model
C characteristics. This vector contains the
C sizes of the state vector and other
6-3
C parameters. More precisely,
6 Creating Fortran S-Functions
6-4
C SIZE(1) number of continuous states
C SIZE(2) number of discrete states
C SIZE(3) number of outputs
C SIZE(4) number of inputs
C SIZE(5) number of discontinuous roots in
C the system
C SIZE(6) set to 1 if the system has direct
C feedthrough of its inputs,
C otherwise 0
C
C=====================================================
C
SUBROUTINE SIZES(SIZE)
C .. Array arguments ..
INTEGER*4 SIZE(*)
C .. Parameters ..
INTEGER*4 NSIZES
PARAMETER (NSIZES=6)
SIZE(1) = 0
SIZE(2) = 0
SIZE(3) = 1
SIZE(4) = 1
SIZE(5) = 0
SIZE(6) = 1
RETURN
END
C
C=====================================================
C
C Function: OUTPUT
C
C Abstract:
C Perform output calculations for continuous
C signals.
C
C=====================================================
C .. Parameters ..
SUBROUTINE OUTPUT(T, X, U, Y)
REAL*8 T
REAL*8 X(*), U(*), Y(*)
Y(1) = U(1) * 2.0
RETURN
END
C
C=====================================================
C
C Stubs for unused functions.
Creating Level 1 Fortran S-Functions
C
C=====================================================
SUBROUTINE INITCOND(X0)
REAL*8 X0(*)
C --- Nothing to do.
RETURN
END
SUBROUTINE DERIVS(T, X, U, DX)
REAL*8 T, X(*), U(*), DX(*)
C --- Nothing to do.
RETURN
END
SUBROUTINE DSTATES(T, X, U, XNEW)
REAL*8 T, X(*), U(*), XNEW(*)
C --- Nothing to do.
RETURN
END
SUBROUTINE DOUTPUT(T, X, U, Y)
REAL*8 T, X(*), U(*), Y(*)
C --- Nothing to do.
RETURN
END
SUBROUTINE TSAMPL(T, X, U, TS, OFFSET)
REAL*8 T,TS,OFFSET,X(*),U(*)
C --- Nothing to do.
RETURN
END
SUBROUTINE SINGUL(T, X, U, SING)
REAL*8 T, X(*), U(*), SING(*)
C --- Nothing to do.
RETURN
END
A Level 1 S-function’s input/output is limited to using the REAL*8 data type,
(DOUBLE PRECISION), which is equivalent to a double in C. Of course, the
internal calculations can use whatever data types you need.
To see how this S-function works, enter
sfcndemo_timestwo_for
at the MATLAB prompt and run the model.
6-5
6 Creating Fortran S-Functions
6-6
Inline Code Generation Example
Real-Time Workshop users can use a sample block target file for
sfun_timestwo_for.mex to generate code for sfcndemo_timestwo_for. If you
want to learn how to inline your own Fortran MEX file, see the example at
matlabroot/toolbox/simulink/blocks/tlc_c/sfun_timestwo_for.tlc and
read the Target Language Compiler Reference Guide.
Creating Level 2 Fortran S-Functions
Creating Level 2 Fortran S-Functions
To use the features of a level 2 S-function with Fortran code, you must write a
skeleton S-function in C that has code for interfacing to Simulink and also calls
your Fortran code.
Using the C-MEX S-function as a gateway is quite simple if you are writing the
Fortran code from scratch. If instead your Fortran code already exists as a
stand-alone simulation, there is some work to be done to identify parts of the
code that need to be registered with Simulink, such as identifying continuous
states if you are using variable-step solvers or getting rid of static variables if
you want to have multiple copies of the S-function in a Simulink model (see
“Porting Legacy Code” on page 6-14).
Template File
The file matlabroot/simulink/src/sfungate.c is a C-MEX template file for
calling into a Fortran subroutine. It works with a simple Fortran subroutine if
you modify the Fortran subroutine name in the code.
C/Fortran Interfacing Tips
The following are some tips for creating the C-to-Fortran gateway S-function.
Mex Environment
Remember that mex -setup needs to find both the C and the Fortran compilers.
If you install or change compilers, you must run mex -setup.
Test the installation and setup using sample MEX files from MATLAB's C and
Fortran MEX examples in matlabroot/extern/examples/mex, as well as
Simulink's examples, which are located in matlabroot/simulink/src.
Compiler Compatibility
Your C and Fortran compilers need to use the same object format. If you use
the compilers explicitly supported by the mex command this is not a problem.
When you use the C gateway to Fortran, it is possible to use Fortran compilers
not supported by the mex command, but only if the object file format is
compatible with the C compiler format. Common object formats include ELF
and COFF.
6-7
6 Creating Fortran S-Functions
6-8
The compiler must also be configurable so that the caller cleans up the stack
instead of the callee. Compaq Visual Fortran (formerly known as Digital
Fortran) is one compiler whose default stack cleanup is the callee.
Symbol Decorations
Symbol decorations can cause run-time errors. For example, g77 decorates
subroutine names with a trailing underscore when in its default configuration.
You can either recognize this and adjust the C function prototype or alter the
Fortran compiler’s name decoration policy via command-line switches, if the
compiler supports this. See the Fortran compiler manual about altering symbol
decoration policies.
If all else fails, use utilities such as od (octal dump) to display the symbol
names. For example, the command
od -s 2 <file>
lists strings and symbols in binary (.obj) files.
These binary utilities can be obtained for Windows as well. MKS is one
company that has commercial versions of powerful UNIX utilities, although
most can also be obtained free on the Web. hexdump is another common
program for viewing binary files. As an example, here is the output of
od -s 2 sfun_atmos_for.o
on Linux.
0000115 Eèù
0000136 Eèù
0000271 Eèo
0000467 ?Eè@
0000530 ?Eè
0000575 EèùE??5@
0001267 Cf|VC-ò:C
0001323 :|.-:8?#8yKw6
0001353 ?333@
0001364 333à
0001414 01.01
0001425 GCC: (GNU) egcs-2.91.66 19990314/Linux
0001522 .symtab
0001532 .strtab
0001542 .shstrtab
0001554 .text
0001562 .rel.text
0001574 .data
0001602 .bss
Creating Level 2 Fortran S-Functions
0001607 .note
0001615 .comment
0003071 sfun_atmos_for.for
0003101 gcc2_compiled.
0003120 rearth.0
0003131 gmr.1
0003137 htab.2
0003146 ttab.3
0003155 ptab.4
0003164 gtab.5
0003173 atmos_
0003207 exp
0003213 pow_d
Note that Atmos has been changed to atmos_, which the C program must call to
be successful.
With Compaq Visual Fortran, the symbol is suppressed, so that Atmos becomes
ATMOS (no underscore).
Fortran Math Library
Fortran math library symbols might not match C math library symbols. For
example, A^B in Fortran calls library function pow_dd, which is not in the C
math library. In these cases, you must tell mex to link in the Fortran math
library. For gcc environments, these routines are usually found in
/usr/local/lib/libf2c.a, /usr/lib/libf2c.a, or equivalent.
The mex command becomes
mex -L/usr/local/lib -lf2c cmex_c_file fortran_object_file
Note On UNIX, the -lf2c option follows the conventional UNIX library
linking syntax, where ’-l’ is the library option itself and ’f2c’ is the unique
part of the library file’s name, libf2c.a. Be sure to use the -L option for the
library search path, because -I is only followed while searching for include
files.
The f2c package can be obtained for Windows and UNIX environments from
the Internet. The file libf2c.a is usually part of g77 distributions, or else the
file is not needed as the symbols match. In obscure cases, it must be installed
separately, but even this is not difficult once the need for it is identified.
6-9
6 Creating Fortran S-Functions
6-10
On Windows, using Microsoft Visual C/C++ and Compaq Visual Fortran 6.0
(formerly known as Digital Fortran), this example can be compiled using the
following mex commands (each command is on one line).
mex -v COMPFLAGS#”$COMPFLAGS /iface:cref” -c sfun_atmos_sub.for
-f ..\..\bin\win32\mexopts\df60opts.bat
mex -v LINKFLAGS#”$LINKFLAGS dfor.lib dfconsol.lib dfport.lib
/LIBPATH:$DF_ROOT\DF98\LIB” sfun_atmos.c sfun_atmos_sub.obj
See matlabroot/simulink/src/sfuntmpl_fortran.txt and
matlabroot/simulink/src/sfun_atmos.c for the latest information on
compiling Fortran for C on Windows.
CFortran
Or you can try using CFortran to create an interface. CFortran is a tool for
automated interface generation between C and Fortran modules, in either
direction. Search the Web for cfortran or visit
http://www-zeus.desy.de/~burow/cfortran/
for downloading.
Obtaining a Fortran Compiler
On Windows, using Visual C/C++ with Fortran is best done with Compaq
Visual Fortran, Absoft, Lahey, or other third-party compilers. See Compaq
(www.compaq.com) and Absoft (www.absoft.com) for Windows, Linux, and Sun
compilers and see Lahey (www.lahey.com) for more choices in Windows Fortran
compilers.
For Sun (Solaris) and other commercial UNIX platforms, you can purchase the
computer vendor’s Fortran compiler, a third-party Fortran such as Absoft, or
even use the Gnu Fortran port for that platform (if available).
As long as the compiler can output the same object (.o) format as the platform’s
C compiler, the Fortran compiler will work with the gateway C-MEX
S-function technique.
Gnu Fortran (g77) can be obtained free for several platforms from many
download sites, including tap://www.redhat.com in the download area. A
useful keyword on search engines is g77.
Creating Level 2 Fortran S-Functions
Constructing the Gateway
The mdlInitializeSizes() and mdlInitializeSampleTimes() methods are
coded in C. It is unlikely that you will need to call Fortran routines from these
S-function methods. In the simplest case, the Fortran is called only from
mdlOutputs().
Simple Case
The Fortran code must at least be callable in one-step-at-a-time fashion. If the
code doesn’t have any states, it can be called from mdlOutputs() and no
mdlDerivatives() or mdlUpdate() method is required.
Code with States
If the code has states, you must decide whether the Fortran code can support a
variable-step solver or not. For fixed-step solver only support, the C gateway
consists of a call to the Fortran code from mdlUpdate(), and outputs are cached
in an S-function DWork vector so that subsequent calls by Simulink into
mdlOutputs() will work properly and the Fortran code won't be called until the
next invocation of mdlUpdate(). In this case, the states in the code can be
stored however you like, typically in the work vector or as discrete states in
Simulink.
If instead the code needs to have continuous time states with support for
variable-step solvers, the states must be registered and stored with Simulink
as doubles. You do this in mdlInitializeSizes() (registering states), then the
states are retrieved and sent to the Fortran code whenever you need to execute
it. In addition, the main body of code has to be separable into a call form that
can be used by mdlDerivatives() to get derivatives for the state integration
and also by the mdlOutputs() and mdlUpdate() methods as appropriate.
Setup Code
If there is a lengthy setup calculation, it is best to make this part of the code
separable from the one-step-at-a-time code and call it from mdlStart(). This
can either be a separate SUBROUTINE called from mdlStart() that
communicates with the rest of the code through COMMON blocks or argument
I/O, or it can be part of the same piece of Fortran code that is isolated by an
IF-THEN-ELSE construct. This construct can be triggered by one of the input
arguments that tells the code if it is to perform either the setup calculations or
the one-step calculations.
6-11
6 Creating Fortran S-Functions
6-12
SUBROUTINE Versus PROGRAM
To be able to call Fortran from Simulink directly without having to launch
processes, etc., you must convert a Fortran PROGRAM into a SUBROUTINE. This
consists of three steps. The first is trivial; the second and third can take a bit
of examination.
1 Change the line PROGRAM to SUBROUTINE subName.
Now you can call it from C using C function syntax.
2 Identify variables that need to be inputs and outputs and put them in the
SUBROUTINE argument list or in a COMMON block.
It is customary to strip out all hard-coded cases and output dumps. In the
Simulink environment, you want to convert inputs and outputs into block
I/O.
3 If you are converting a stand-alone simulation to work inside Simulink,
identify the main loop of time integration and remove the loop and, if you
want Simulink to integrate continuous states, remove any time integration
code. Leave time integrations in the code if you intend to make a discrete
time (sampled) S-function.
Arguments to a SUBROUTINE
Most Fortran compilers generate SUBROUTINE code that passes arguments by
reference. This means that the C code calling the Fortran code must use only
pointers in the argument list.
PROGRAM ...
becomes
SUBROUTINE somename( U, X, Y )
A SUBROUTINE never has a return value. You manage I/O by using some of the
arguments for input, the rest for output.
Arguments to a FUNCTION
A FUNCTION has a scalar return value passed by value, so a calling C program
should expect this. The argument list is passed by reference (i.e., pointers) as
in the SUBROUTINE.
Creating Level 2 Fortran S-Functions
If the result of a calculation is an array, then you should use a subroutine, as a
FUNCTION cannot return an array.
Interfacing to COMMON blocks
While there are several ways for Fortran COMMON blocks to be visible to C code,
it is often recommended to use an input/output argument list to a SUBROUTINE
or FUNCTION. If the Fortran code has already been written and uses COMMON
blocks, it is a simple matter to write a small SUBROUTINE that has an
input/output argument list and copies data into and out of the COMMON block.
The procedure for copying in and out of the COMMON block begins with a write of
the inputs to the COMMON block before calling the existing SUBROUTINE. The
SUBROUTINE is called, then the output values are read out of the COMMON block
and copied into the output variables just before returning.
Example C-MEX S-Function Calling Fortran Code
The subroutine Atmos is in file sfun_atmos_sub.for. The gateway C-MEX
S-function is sfun_atmos.c, which is built on UNIX using the command
mex -L/usr/local/lib -lf2c sfun_atmos.c sfun_atmos_sub.o
On Windows, the command is
>> mex -v COMPFLAGS#”$COMPFLAGS /iface:cref” -c sfun_atmos_sub.for
-f ..\..\bin\win32\mexopts\df60opts.bat
>> mex -v LINKFLAGS#”$LINKFLAGS dfor.lib dfconsol.lib dfport.lib
/LIBPATH:$DF_ROOT\DF98\LIB” sfun_atmos.c sfun_atmos_sub.obj
On some UNIX systems where the C and Fortran compilers were installed
separately (or aren’t aware of each other), you might need to reference the
library libf2c.a. To do this, use the -lf2c flag.
UNIX only: if the libf2c.a library isn’t on the library path, you need to add the
path to the mex process explicitly with the -L command. For example:
mex -L/usr/local/lib/ -lf2c sfun_atmos.c sfun_atmos_sub.o
This sample is prebuilt and is on the MATLAB search path already, so you can
see it working by opening the sample model sfcndemo_atmos.mdl. Enter
sfcndemo_atmos
at the command prompt, or to get all the S-function demos for Simulink, type
6-13
sfcndemos at the MATLAB prompt.
6 Creating Fortran S-Functions
6-14
Porting Legacy Code
Find the States
If a variable-step solver is being used, it is critical that all continuous states are
identified in the code and put into Simulink’s state vector for integration
instead of being integrated by the Fortran code. Likewise, all derivative
calculations must be made available separately to be called from the
mdlDerivatives() method in the S-function. Without these steps, any Fortran
code with continuous states will not be compatible with variable-step solvers if
the S-function is registered as a continuous block with continuous states.
Telltale signs of implicit advancement are incremented variables such as M=M+1
or X=X+0.05. If the code has many of these constructs and you determine that
it is impractical to recode the source so as not to “ratchet forward,” you might
need to try another approach using fixed-step solvers.
If it is impractical to find all the implicit states and to separate out the
derivative calculations for Simulink, another approach can be used, but you are
limited to using fixed-step solvers. The technique here is to call the Fortran
code from the mdlUpdate() method so the Fortran code is only executed once
per Simulink major integration step. Any block outputs must be cached in a
work vector so that mdlOutputs() can be called as often as needed and output
the values from the work vector instead of calling the Fortran routine again
(causing it to inadvertently advance time). See
matlabroot/simulink/src/sfuntmpl_gate_fortran.c for an example that
uses DWork vectors.
Sample Times
If the code has an implicit step size in its algorithm, coefficients, etc., ensure
that you register the proper discrete sample time in the
mdlInitializeSampleTimes() S-function method and only change the block's
output values from the mdlUpdate() method.
Multiple Instances
If you plan to have multiple copies of this S-function used in one Simulink
model, you need to allocate storage for each copy of the S-function in the model.
The recommended approach is to use DWork vectors. See
matlabroot/simulink/include/simstruc.h and
Porting Legacy Code
matlabroot/simulink/src/sfuntmpl_doc.c for details on allocating
data-typed work vectors.
Use Flints If Needed
Use flints (floating-point ints) to keep track of time. Flints (for IEEE-754
floating-point numerics) have the useful property of not accumulating roundoff
error when adding and subtracting flints. Using flint variables in DOUBLE
PRECISION storage (with integer values) avoids roundoff error accumulation
that would accumulate when floating-point numbers are added together
thousands of times.
DOUBLE PRECISION F
:
:
F = F + 1.0
TIME = 0.003 * F
This technique avoids a common pitfall in simulations.
Considerations for Real Time
Since very few Fortran applications are used in a real-time environment, it is
common to come across simulation code that is incompatible with a real-time
environment. Common failures include unbounded (or large) iterations and
sporadic but time-intensive side calculations. You must deal with these directly
if you expect to run in real time.
Conversely, it is still perfectly good practice to have iterative or sporadic
calculations if the generated code is not being used for a real-time application.
6-15
6 Creating Fortran S-Functions
6-16
7
Implementing Block
Features
The following sections how to use S-function callback methods to implement various block features.
Dialog Parameters (p. 7-2) How to process parameters passed via the S-function
block’s dialog box.
Run-Time Parameters (p. 7-5) How to create and use run-time parameters.
Creating Input and Output Ports
(p. 7-8)
How to create input and output ports on a block.
Custom Data Types (p. 7-14) How to create custom data types for the values of a
block’s signals and parameters.
Sample Times (p. 7-15) How to specify the rate or rates at which your block
operates.
Work Vectors (p. 7-26) How to create and use work vectors.
Function-Call Subsystems (p. 7-31) How to create a function-call subsystem.
Handling Errors (p. 7-33) How to handle errors in an S-function.
S-Function Examples (p. 7-36) Examples of S-functions.
7 Implementing Block Features
7-2
Dialog Parameters
A user can pass parameters to an S-function at the start of and, optionally,
during the simulation, using the S-Function parameters field of the block’s
dialog box. Such parameters are called dialog box parameters to distinguish
them from run-time parameters created by the S-function to facilitate code
generation (see “Run-Time Parameters” on page 7-5). Simulink stores the
values of the dialog box parameters in the S-function’s SimStruct structure.
Simulink provides callback methods and SimStruct macros that allow the
S-function to access and check the parameters and use them in the
computation of the block’s output.
If you want your S-function to be able to use dialog parameters, you must
perform the following steps when you create the S-function:
1 Determine the order in which the parameters are to be specified in the
block’s dialog box.
2 In the mdlInitializeSizes function, use the ssSetNumSFcnParams macro to
tell Simulink how many parameters the S-function accepts. Specify S as the
first argument and the number of parameters you are defining interactively
as the second argument. If your S-function implements the
mdlCheckParameters method, the mdlInitializeSizes routine should call
mdlCheckParameters to check the validity of the initial values of the
parameters.
3 Access these input arguments in the S-function using the ssGetSFcnParam
macro.
Specify S as the first argument and the relative position of the parameter in
the list entered on the dialog box (0 is the first position) as the second
argument. The ssGetSFcnParam macro returns a pointer to the mxArray
containing the parameter. You can use ssGetDTypeIdFromMxArray to get the
data type of the parameter.
When running a simulation, the user must specify the parameters in the
S-Function parameters field of the block’s dialog box in the same order that
you defined them in step 1. The user can enter any valid MATLAB expression
as the value of a parameter, including literal values, names of workspace
variables, function invocations, or arithmetic expressions. Simulink evaluates
the expression and passes its value to the S-function.
Dialog Parameters
For example, the following code is part of a device driver S-function. Four input
parameters are used: BASE_ADDRESS_PRM, GAIN_RANGE_PRM, PROG_GAIN_PRM,
and NUM_OF_CHANNELS_PRM. The code uses #define statements to associate
particular input arguments with the parameter names.
/* Input Parameters */
#define BASE_ADDRESS_PRM(S) ssGetSFcnParam(S, 0)
#define GAIN_RANGE_PRM(S) ssGetSFcnParam(S, 1)
#define PROG_GAIN_PRM(S) ssGetSFcnParam(S, 2)
#define NUM_OF_CHANNELS_PRM(S) ssGetSFcnParam(S, 3)
When running the simulation, a user enters four variable names or values in
the S-Function parameters field of the block’s dialog box. The first
corresponds to the first expected parameter, BASE_ADDRESS_PRM(S). The
second corresponds to the next expected parameter, and so on.
The mdlInitializeSizes function contains this statement.
ssSetNumSFcnParams(S, 4);
Tunable Parameters
Dialog parameters can be either tunable or nontunable. A tunable parameter
is a parameter that a user can change while the simulation is running. Use the
macro ssSetSFcnParamTunable in mdlInitializeSizes to specify the
tunability of each dialog parameter used by the macro.
Note Dialog parameters are tunable by default. Nevertheless, it is good
programming practice to set the tunability of every parameter, even those that
are tunable. If the user enables the simulation diagnostic S-function
upgrade needed, Simulink issues the diagnostic whenever it encounters an
S-function that fails to specify the tunability of all its parameters.
The mdlCheckParameters method enables you to validate changes to tunable
parameters during a simulation run. Simulink invokes the
mdlCheckParameters method whenever a user changes the values of
parameters during the simulation loop. This method should check the
S-function’s dialog parameters to ensure that the changes are valid.
7-3
7 Implementing Block Features
7-4
Note The S-function’s mdlInitializeSizes routine should also invoke the
mdlCheckParameters method to ensure that the initial values of the
parameters are valid.
The optional mdlProcessParameters callback method allows an S-function to
process changes to tunable parameters. Simulink invokes this method only if
valid parameter changes have occurred in the previous time step. A typical use
of this method is to perform computations that depend only on the values of
parameters and hence need to be computed only when parameter values
change. The method can cache the results of the parameter computations in
work vectors or, preferably, as run-time parameters (see “Run-Time
Parameters” on page 7-5).
Tuning Parameters in External Mode
When a user tunes parameters during simulation, Simulink invokes the
S-function’s mdlCheckParameters method to validate the changes and then the
S-functions’ mdlProcessParameters method to give the S-function a chance to
process the parameters in some way. Simulink also invokes these methods
when running in external mode, but it passes the unprocessed changes on to
the S-function target. Thus, if it is essential that your S-function process
parameter changes, you need to create a Target Language Compiler (TLC) file
that inlines the S-function, including its parameter processing code, during the
code generation process. For information on inlining S-functions, see the
Target Language Compiler Reference Guide.
Run-Time Parameters
Run-Time Parameters
Simulink allows an S-function to create and use internal representations of
external dialog parameters called run-time parameters. Every run-time
parameter corresponds to one or more dialog parameters and can have the
same value and data type as its corresponding external parameters or a
different value or data type. If a run-time parameter differs in value or data
type from its external counterpart, the dialog parameter is said to have been
transformed to create the run-time parameter. The value of a run-time
parameter that corresponds to multiple dialog parameters is typically a
function of the values of the dialog parameters. Simulink allocates and frees
storage for run-time parameters and provides functions for updating and
accessing them, thus eliminating the need for S-functions to perform these
tasks.
Run-time parameters facilitate the following kinds of S-function operations:
Computed parameters
Often the output of a block is a function of the values of several dialog
parameters. For example, suppose a block has two parameters, the volume
and density of some object, and the output of the block is a function of the
input signal and the weight of the object. In this case, the weight can be
viewed as a third internal parameter computed from the two external
parameters, volume and density. An S-function can create a run-time
parameter corresponding to the computed weight, thereby eliminating the
need to provide special case handling for weight in the output computation.
Data type conversions
Often a block needs to change the data type of a dialog parameter to facilitate
internal processing. For example, suppose that the output of the block is a
function of the input and a parameter and the input and parameter are of
different data types. In this case, the S-function can create a run-time
parameter that has the same value as the dialog parameter but has the data
type of the input signal, and use the run-time parameter in the computation
of the output.
Code generation
During code generation, Real-Time Workshop writes all run-time
parameters automatically to the model.rtw file, eliminating the need for the
S-function to perform this task via an mdlRTW method.
7-5
7 Implementing Block Features
7-6
Creating Run-Time Parameters
An S-function can create run-time parameters all at once or one by one.
Creating Run-Time Parameters All at Once
Use the SimStruct function ssRegAllTunableParamsAsRunTimeParams in
mdlSetWorkWidths to create run-time parameters corresponding to all tunable
parameters. This function requires that you pass it an array of names, one for
each run-time parameter. Real-Time Workshop uses this name as the name of
the parameter during code generation.
This approach to creating run-time parameters assumes that there is a
one-to-one correspondence between an S-function’s run-time parameters and
its tunable dialog parameters. This might not be the case. For example, an
S-function might want to use a computed parameter whose value is a function
of several dialog parameters. In such cases, the S-function might need to create
the run-time parameters individually.
Creating Run-Time Parameters Individually
To create run-time parameters individually, the S-function’s
mdlSetWorkWidths method should
1 Specify the number of run-time parameters it intends to use, using
ssSetNumRunTimeParams.
2 Use ssRegDlgParamAsRunTimeParam to register a run-time parameter that
corresponds to a single, untransformed dialog parameter or
ssSetRunTimeParamInfo to set the attributes of a run-time parameter that
corresponds to more than one dialog parameter or a transformed dialog
parameter.
Note The first four characters of block’s run-time parameter names must be
unique. If they are not, Simulink signals an error. For example, trying to
register a parameter named param2 triggers an error if a parameter named
param1 already exists.
Run-Time Parameters
Updating Run-Time Parameters
Whenever a user changes the values of an S-function’s dialog parameters
during a simulation run, Simulink invokes the S-function’s
mdlCheckParameters method to validate the changes. If the changes are valid,
Simulink invokes the S-function’s mdlProcessParameters method at the
beginning of the next time step. This method should update the S-function’s
run-time parameters to reflect the changes in the dialog parameters.
Updating All Parameters at Once
If there is a one-to-one correspondence between the S-function’s tunable dialog
parameters and the run-time parameters, the S-function can use the
SimStruct function ssUpdateAllTunableParamsAsRunTimeParams to
accomplish this task. This function updates each run-time parameter to have
the same value as the corresponding dialog parameter.
Updating Parameters Individually
If there is not a one-to-one correspondence between the S-function’s dialog and
run-time parameters or the run-time parameters are transformed versions of
the dialog parameters, the mdlProcessParameters method must update each
parameter individually.
If a run-time parameter and its corresponding dialog parameter differ only in
value, the method can use ssUpdateRunTimeParamData to update the run-time
parameter. This function updates the data field in the parameter’s attributes
record, ssParamRec, with a new value. If the run-time parameter and the dialog
parameter differ only in value and data type, the method can use
ssUpdateDlgParamAsRunTimeParam to update the run-time parameter.
Otherwise, the mdlProcessParameters method must update the parameter’s
attributes record itself. To update the attributes record, the method should
1 Get a pointer to the parameter’s attributes record, using
ssGetRunTimeParamInfo.
2 Update the attributes record to reflect the changes in the corresponding
dialog parameters.
3 Register the changes, using ssUpdateRunTimeParamInfo.
7-7
7 Implementing Block Features
7-8
Creating Input and Output Ports
Simulink allows S-functions to create and use any number of block I/O ports.
This section shows how to create and initialize I/O ports and how to change the
characteristics of an S-function block’s ports, such as dimensionality and data
type, based on its connections to other blocks.
Creating Input Ports
To create and configure input ports, the mdlInitializeSizes method should
first specify the number of input ports that the S-function has, using
ssSetNumInputPorts. Then, for each input port, the method should specify
The dimensions of the input port (see “Initializing Input Port Dimensions”
on page 7-9)
If you want your S-function to inherit its dimensionality from the port to
which it is connected, you should specify that the port is dynamically sized
in mdlInitializeSizes (see “Sizing an Input Port Dynamically” on
page 7-9).
Whether the input port allows scalar expansion of inputs (see “Scalar
Expansion of Inputs” on page 7-11)
Whether the input port has direct feedthrough, using
ssSetInputPortDirectFeedThrough
A port has direct feedthrough if the input is used in either the mdlOutputs or
mdlGetTimeOfNextVarHit functions. The direct feedthrough flag for each
input port can be set to either 1=yes or 0=no. It should be set to 1 if the input,
u, is used in the mdlOutputs or mdlGetTimeOfNextVarHit routine. Setting
the direct feedthrough flag to 0 tells Simulink that u is not used in either of
these S-function routines. Violating this leads to unpredictable results.
The data type of the input port, if not the default double
Use ssSetInputPortDataType to set the input port’s data type. If you want
the data type of the port to depend on the data type of the port to which it is
connected, specify the data type as DYNAMICALLY_TYPED. In this case, you
must provide implementations of the mdlSetInputPortDataType and
mdlSetDefaultPortDataTypes methods to enable the data type to be set
correctly during signal propagation.
Creating Input and Output Ports
The numeric type of the input port, if the port accepts complex-valued signals
Use ssSetInputComplexSignal to set the input port’s numeric type. If you
want the numeric type of the port to depend on the numeric type of the port
to which it is connected, specify the data type as inherited. In this case, you
must provide implementations of the mdlSetInputPortComplexSignal and
mdlSetDefaultPortComplexSignal methods to enable the numeric type to
be set correctly during signal propagation.
Note The mdlInitializeSizes method must specify the number of ports
before setting any properties. If it attempts to set a property of a port that
doesn't exist, it is accessing invalid memory and Simulink crashes.
Initializing Input Port Dimensions
The following options exist for setting the input port dimensions:
If the input signal is one-dimensional and the input port width is w, use
ssSetInputPortVectorDimension(S, inputPortIdx, w)
If the input signal is a matrix of dimension m-by-n, use
ssSetInputPortMatrixDimensions(S, inputPortIdx, m, n)
Otherwise use
ssSetInputPortDimensionInfo(S, inputPortIdx, dimsInfo)
You can use this function to fully or partially initialize the port dimensions
(see next section).
Sizing an Input Port Dynamically
If your S-function does not require that an input signal have a specific
dimensionality, you might want to set the dimensionality of the input port to
match the dimensionality of the signal connected to the port. To dimension an
input port dynamically, your S-function should
Specify some or all of the dimensions of the input port as dynamically sized
in mdlInitializeSizes.
If the input port can accept a signal of any dimensionality, use
7-9
7 Implementing Block Features
7-10
ssSetInputPortDimensionInfo(S, inputPortIdx, DYNAMIC_DIMENSION)
to set the dimensionality of the input port.
If the input port can accept only vector (1-D) signals but the signals can be of
any size, use
ssSetInputPortWidth(S, inputPortIdx, DYNAMICALLY_SIZED)
to specify the dimensionality of the input port.
If the input port can accept only matrix signals but can accept any row or
column size, use
ssSetInputPortMatrixDimensions(S, inputPortIdx, m, n)
where m and/or n are DYNAMICALLY_SIZED.
Provide an mdlSetInputPortDimensionInfo method that sets the
dimensions of the input port to the size of the signal connected to it.
Simulink invokes this method during signal propagation when it has
determined the dimensionality of the signal connected to the input port.
Provide an mdlSetDefaultPortDimensionInfo method that sets the
dimensions of the block’s ports to a default value.
Simulink invokes this method during signal propagation when it cannot
determine the dimensionality of the signal connected to some or all of the
block’s input ports. This can happen, for example, if an input port is
unconnected. If the S-function does not provide this method, Simulink sets
the dimension of the block’s ports to 1-D scalar.
Creating Output Ports
To create and configure output ports, the mdlInitializeSizes method should
first specify the number of input ports that the S-function has, using
ssSetNumOutputPorts. Then, for each output port, the method should specify
Dimensions of the output port
Simulink provides the following macros for setting the port’s dimensions.
- ssSetOutputPortDimensionInfo
- ssSetOutputPortMatrixDimensions
- ssSetOutputPortVectorDimensions
Creating Input and Output Ports
- ssSetOutputWidth
If you want the port’s dimensions to depend on block connectivity, set the
dimensions to DYNAMICALLY_SIZED. The S-function must then provide
mdlSetOutputPortDimensionInfo and ssSetDefaultPortDimensionInfo
methods to ensure that output port dimensions are set to the correct values
in code generation.
Data type of the output port
Use ssSetOutputPortDataType to set the output port’s data type. If you want
the data type of the port to depend on block connectivity, specify the data
type as DYNAMICALLY_TYPED. In this case, you must provide implementations
of the mdlSetOutputPortDataType and mdlSetDefaultPortDataTypes
methods to enable the data type to be set correctly during signal propagation.
The numeric type of the input port, if the port outputs complex-valued
signals
Use ssSetOutputComplexSignal to set the output port’s numeric type. If you
want the numeric type of the port to depend on the numeric type of the port
to which it is connected, specify the data type as inherited. In this case, you
must provide implementations of the mdlSetOutputPortComplexSignal and
mdlSetDefaultPortComplexSignal methods to enable the numeric type to
be set correctly during signal propagation.
Scalar Expansion of Inputs
Scalar expansion of inputs refers conceptually to the process of expanding
scalar input signals to have the same dimensions as the ports to which they are
connected. This is done by setting each element of the expanded signal to the
value of the scalar input. An S-function’s mdlInitializeSizes method can
enable scalar expansion of inputs for its input ports by setting the
SS_OPTION_ALLOW_INPUT_SCALAR_EXPANSION option, using ssSetOptions.
The best way to understand the scalar expansion rules is to consider a Sum
block with two input ports, where the first input signal is scalar, the second
input signal is a 1-D vector with w > 1 elements, and the output signal is a 1-D
vector with w elements. In this case, the scalar input is expanded to a 1-D vector
with w elements in the output method, and each element of the expanded signal
is set to the value of the scalar input.
Outputs
7-11
<snip>
7 Implementing Block Features
7-12
u1inc = (u1width > 1);
u2inc = (u2width > 1);
for (i=0;i<w;i++) {
y[i] = *u1 + *u2;
u1 += u1inc;
u2 += u2inc;
}
If the block has more than two inputs, each input signal must be scalar, or the
wide signals must have the same number of elements. In addition, if the wide
inputs are driven by 1-D and 2-D vectors, the output is a 2-D vector signal, and
the scalar inputs are expanded to a 2-D vector signal.
The way scalar expansion actually works depends on whether the S-function
manages the dimensions of its input and output ports using
mdlSetInputPortWidth and mdlSetOutputPortWidth or
mdlSetInputPortDimensionInfo, mdlSetOutputPortDimensionInfo, and
mdlSetDefaultPortDimensionInfo.
If the S-function does not specify/control the dimensions of its input and output
ports using the preceding methods, Simulink uses a default method to set the
input and output ports.
In the mdlInitializeSizes method, the S-function can enable scalar
expansion for its input ports by setting the
SS_OPTION_ALLOW_INPUT_SCALAR_EXPANSION option, using ssSetOptions. The
Simulink default method uses the preceding option to allow or disallow scalar
expansion for a block’s input ports. If the preceding option is not set by an
S-function, Simulink assumes that all ports (input and output ports) must have
the same dimensions, and it sets all port dimensions to the same dimensions
specified by one of the driving blocks.
If the S-function specifies/controls the dimensions of its input and output ports,
Simulink ignores the SCALAR_EXPANSION option.
See matlabroot/simulink/src/sfun_multiport.c for an example.
Masked Multiport S-Functions
If you are developing masked multiport S-function blocks whose number of
ports varies based on some parameter, and if you want to place them in a
Simulink library, you must specify that the mask modifies the appearance of
the block. To do this, execute the command
Creating Input and Output Ports
set_param('block','MaskSelfModifiable','on')
at the MATLAB prompt before saving the library. Failure to specify that the
mask modifies the appearance of the block means that an instance of the block
in a model reverts to the number of ports in the library whenever you load the
model or update the library link.
7-13
7 Implementing Block Features
7-14
Custom Data Types
An S-function can accept and output user-defined as well as built-in Simulink
data types. To use a user-defined data type, the S-function’s
mdlInitializeSizes routine must
1 Register the data type, using ssRegisterDataType.
2 Specify the amount of memory in bytes required to store an instance of the
data type, using ssSetDataTypeSize.
3 Specify the value that represents zero for the data type, using
ssSetDataTypeZero.
Sample Times
Sample Times
Simulink supports blocks that execute at different rates. An S-function block
can specify its rates (i.e., sample times) as
Block-based sample times
Port-based sample times
Hybrid block-based and port-based sample times
With block-based sample times, the S-function specifies a set of operating rates
for the block as a whole during the initialization phase of the simulation.With
port-based sample times, the S-function specifies a sample time for each input
and output port individually during initialization. During the execution phase,
with block-based sample times, the S-function processes all inputs and outputs
each time a sample hit occurs for the block. By contrast, with port-based
sample times, the block processes a particular port only when a sample hit
occurs for that port.
For example, consider two sample rates, 0.5 and 0.25 seconds, respectively:
In the block-based method, selecting 0.5 and 0.25 would direct the block to
execute inputs and outputs at 0.25 second increments.
In the port-based method, you could set the input port to 0.5 and the output
port to 0.25, and the block would process inputs at 2Hz and outputs at 4Hz.
You should use port-based sample times if your application requires unequal
sample rates for input and output execution or if you don’t want the overhead
associated with running input and output ports at the highest sample rate of
your block.
In some applications, an S-Function block might need to operate internally at
one or more sample rates while inputting or outputting signals at other rates.
The hybrid block- and port-based method of specifying sample rates allows you
to create such blocks.
In typical applications, you specify only one block-based sample time.
Advanced S-functions might require the specification of port-based or multiple
block sample times.
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7 Implementing Block Features
7-16
Block-Based Sample Times
The next two sections discuss how to specify block-based sample times. You
must specify information in
mdlInitializeSizes
mdlInitializeSampleTimes
A third section presents a simple example that shows how to specify sample
times in mdlInitializeSampleTimes.
Specifying the Number of Sample Times in mdlInitializeSizes. To configure your
S-function block for block-based sample times, use
ssSetNumSampleTimes(S,numSampleTimes);
where numSampleTimes > 0. This tells Simulink that your S-function has
block-based sample times. Simulink calls mdlInitializeSampleTimes, which
in turn sets the sample times.
Setting Sample Times and Specifying Function Calls in
mdlInitializeSampleTimes
mdlInitializeSampleTimes is used to specify two pieces of execution
information:
Sample and offset times — In mdlInitializeSizes, specify the number of
sample times you’d like your S-function to have by using the
ssSetNumSampleTimes macro. In mdlInitializeSampleTimes, you must
specify the sampling period and offset for each sample time.
Sample times can be a function of the input/output port widths. In
mdlInitializeSampleTimes, you can specify that sample times are a
function of ssGetInputPortWidth and ssGetOutputPortWidth.
Function calls — In ssSetCallSystemOutput, specify the output elements
that are performing function calls. See
matlabroot/simulink/src/sfun_fcncall.c for an example.
You specify the sample times as pairs [sample_time, offset_time], using
these macros
ssSetSampleTime(S, sampleTimePairIndex, sample_time)
ssSetOffsetTime(S, offsetTimePairIndex, offset_time)
where sampleTimePairIndex starts at 0.
Sample Times
The valid sample time pairs are (uppercase values are macros defined in
simstruc.h).
[CONTINUOUS_SAMPLE_TIME, 0.0 ]
[CONTINUOUS_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]
[discrete_sample_period, offset ]
[VARIABLE_SAMPLE_TIME , 0.0 ]
Alternatively, you can specify that the sample time is inherited from the
driving block, in which case the S-function can have only one sample time pair,
[INHERITED_SAMPLE_TIME, 0.0 ]
or
[INHERITED_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]
The following guidelines might help in specifying sample times:
A continuous function that changes during minor integration steps should
register the [CONTINUOUS_SAMPLE_TIME, 0.0] sample time.
A continuous function that does not change during minor integration steps
should register the
[CONTINUOUS_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET] sample time.
A discrete function that changes at a specified rate should register the
discrete sample time pair
[discrete_sample_period, offset]
where
discrete_sample_period > 0.0
and
0.0 <= offset < discrete_sample_period
A discrete function that changes at a variable rate should register the
variable-step discrete [VARIABLE_SAMPLE_TIME, 0.0] sample time. The
mdlGetTimeOfNextVarHit function is called to get the time of the next
sample hit for the variable-step discrete task. The VARIABLE_SAMPLE_TIME
can be used with variable-step solvers only.
If your function has no intrinsic sample time, you must indicate that it is
7-17
inherited according to the following guidelines:
7 Implementing Block Features
7-18
A function that changes as its input changes, even during minor integration
steps, should register the [INHERITED_SAMPLE_TIME, 0.0] sample time.
A function that changes as its input changes, but doesn’t change during
minor integration steps (that is, is held during minor steps), should register
the [INHERITED_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET] sample
time.
To check for a sample hit during execution (in mdlOutputs or mdlUpdate), use
the ssIsSampleHit or ssIsContinuousTask macro. For example, if your first
sample time is continuous, then you used the following code fragment to check
for a sample hit. Note that you get incorrect results if you use
ssIsSampleHit(S,0,tid).
if (ssIsContinuousTask(S,tid)) {
}
If, for example, you wanted to determine whether the third (discrete) task has
a hit, you would use the following code fragment:
if (ssIsSampleHit(S,2,tid) {
}
Example: mdlInitializeSampleTimes
This example specifies that there are two discrete sample times with periods of
0.01 and 0.5 seconds.
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, 0.01);
ssSetOffsetTime(S, 0, 0.0);
ssSetSampleTime(S, 1, 0.5);
ssSetOffsetTime(S, 1, 0.0);
} /* End of mdlInitializeSampleTimes. */
Specifying Port-Based Sample Times
If you want your S-function to use port-based sample times, you must specify
the number of sample times as port-based in the S-function’s
mdlInitializeSizes method:
ssSetNumSampleTimes(S, PORT_BASED_SAMPLE_TIMES)
Sample Times
You must also specify the sample time of each input and output port in the
S-function’s mdlInitializeSizes method, using the following macros
ssSetInputPortSampleTime(S, idx, period)
ssSetInputPortOffsetTime(S, idx, offset)
ssSetOutputPortSampleTime(S, idx, period)
ssSetOutputPortOffsetTime(S, idx, offset)
Note mdlInitializeSizes should not contain any ssSetSampleTime or
ssSetOffsetTime calls when you use port-based sample times.
For any given port, you can specify
A specific sample time and period
For example, the following code sets the sample time of the S-function’s first
input port to every 0.1 s starting with the simulation start time.
ssSetInputPortSampleTime(S, 0, 0.1);
ssSetInputPortOffsetTime(S, 0, 0);
Inherited sample time, i.e., the port inherits its sample time from the port to
which it is connected (see “Specifying Inherited Sample Time for a Port” on
page 7-19)
Constant sample time, i.e., the port’s input or output never changes (see
“Specifying Constant Sample Time for a Port” on page 7-20)
Note To be usable in a triggered subsystem, all of your S-function’s ports
must have either inherited or constant sample time (see “Configuring
Port-Based Sample Times for Use in Triggered Subsystems” on page 7-21).
Specifying Inherited Sample Time for a Port
To specify that a port’s sample time is inherited, the mdlInitializeSizes
method should set its period to -1 and its offset to 0. For example, the following
code specifies inherited sample time for the S-function’s first input port:
ssSetInputPortSampleTime(S, 0, -1);
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7 Implementing Block Features
7-20
ssSetInputPortOffsetTime(S, 0, 0);
When you specify port-based sample times, Simulink calls
mdlSetInputPortSampleTime and mdlSetOutputPortSampleTime to determine
the rates of inherited signals.
Once all rates have been determined, Simulink calls
mdlInitializeSampleTimes. Even though there is no need to initialize
port-based sample times at this point, Simulink invokes this method to give
your S-function an opportunity to configure function-call connections. Your
S-function must thus provide an implementation for this method regardless of
whether it uses port-based sample times or function-call connections. Although
you can provide an empty implementation, you might want to use it to check
the appropriateness of the sample times that the block inherited during sample
time propagation.
Specifying Constant Sample Time for a Port
If your S-function uses port-based sample times, it can specify that any of its
ports has a constant sample time. This means that the signal entering or
leaving the port never changes from its initial value at the start of the
simulation.
Before specifying constant sample time for an output port whose output
depends on the S-function’s parameters, the S-function should use
ssGetInlineParameters to check whether the user has specified the Inline
parameters option on the Advanced pane of the Simulation parameters
dialog box. If the user has not checked this option, it is possible for the user to
change the values the S-function’s parameters and hence its outputs during the
simulation. In this case, the S-function should not specify a constant sample
time for any ports whose outputs depend on the S-function’s parameters.
To specify constant sample time for a port, the S-function must perform the
following tasks
Tell Simulink that it supports constant port sample times in its
mdlInitializeSizes method:
ssSetOptions(S, SS_OPTION_ALLOW_CONSTANT_PORT_SAMPLE_TIME);
Sample Times
Note By setting this option, your S-function is in effect telling Simulink that
all of its ports support a constant sample time including ports that inherit
their sample times from other blocks. If any of the S-function’s inherited
sample time ports cannot have a constant sample time, your S-function’s
mdlSetInputPortSampleTime and mdlSetOutputPortSampleTime methods
must eheck whether that port has inherited a constant sample time. If the
port has inherited a constant sample time, your S-function should throw an
error.
Set the port’s period to inf and its offset to 0, e.g.,
ssSetInputPortSampleTime(S, 0, mxGetInf());
ssSetInputPortOffsetTime(S, 0, 0);
Check in mdlOutputs whether the method’s tid argument equals
CONSTANT_TID and if so, set the value of the port’s output if it is an output
port.
See sfun_port_constant.c, the source file for the sfcndemo_port_constant
demo, for an example of how to create ports with a constant sample time.
Configuring Port-Based Sample Times for Use in Triggered Subsystems
To be usable in a triggered subsystem, your port-based sample time S-function
must perform the following tasks.
Tell Simulink in its mdlInitializeSizes method that it can run in a
triggered subsystem:
ssSetOptions(S,
SS_OPTION_ALLOW_PORT_BASED_SAMPLE_TIME_IN_TRIGSS);
Set all of its ports to have either inherited or constant sample time in its
mdlInitializeSizes method.
Handle inheritance of a triggered sample time in
mdlSetInputPortSampleTime and mdlSetOutputPortSampleTime methods
as follows.
If the S-function resides in a triggered subsystem, Simulink invokes either
mdlSetInputPortSampleTime or mdlSetOutputPortSampleTime once per
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7 Implementing Block Features
7-22
time step. Whichever method is called must set the sample time and offset of
the port for which it is called to INHERITED_SAMPLE_TIME (-1), e.g.,
ssSetInputPortSampleTime(S, 0, INHERITED_SAMPLE_TIME);
ssSetInputPortOffsetTime(S, 0, INHERITED_SAMPLE_TIME);
Setting a port’s sample time and offset both to INHERITED_SAMPLE_TIME
indicates that the sample time of the port is triggered, i.e., it produces an
output or accepts an input only when the subsystem in which it resides is
triggered. The method must also set the sample times and offsets of all of the
S-function’s other input and output ports to have either triggered or constant
sample time, whichever is appropriate.
There is no way for an S-function residing in a triggered subsystem to predict
whether Simulink will call mdlSetInputPortSampleTime or
mdlSetOutputPortSampleTime to set its port sample times. For this reason,
both methods must be able to set the sample times correctly.
In mdlUpdate and mdlOutputs, use
ssGetPortBasedSampleTimeBlockIsTriggered to check whether the
S-function resides in a triggered subsystem and if so, use appropriate
algorithms for computing its states and outputs.
See sfun_port_triggered.c, the source file for the sfcndemo_port_triggered
demo, for an example of how to create ports with a constant sample time.
Hybrid Block-Based and Port-Based Sample Times
The hybrid method of assigning sample times combines the block-based and
port-based methods. You first specify, in mdlInitializeSizes, the total
number of rates at which your block operates, including both internal and
input and output rates, using ssSetNumSampleTimes. You then set the
SS_OPTION_PORT_SAMPLE_TIMES_ASSIGNED, using ssSetOptions, to tell the
simulation engine that you are going to use the port-based method to specify
the rates of the input and output ports individually. Next, as in the block-based
method, you specify the periods and offsets of all of the block’s rates, both
internal and external, using
ssSetSampleTime
ssSetOffsetTime
Finally, as in the port-based method, you specify the rates for each port, using
ssSetInputPortSampleTime(S, idx, period)
Sample Times
ssSetInputPortOffsetTime(S, idx, offset)
ssSetOutputPortSampleTime(S, idx, period)
ssSetOutputPortOffsetTime(S, idx, offset)
Note that each of the assigned port rates must be the same as one of the
previously declared block rates.
Multirate S-Function Blocks
In a multirate S-Function block, you can encapsulate the code that defines each
behavior in the mdlOutputs and mdlUpdate functions with a statement that
determines whether a sample hit has occurred. The ssIsSampleHit macro
determines whether the current time is a sample hit for a specified sample
time. The macro has this syntax:
ssIsSampleHit(S, st_index, tid)
where S is the SimStruct, st_index identifies a specific sample time index, and
tid is the task ID (tid is an argument to the mdlOutputs and mdlUpdate
functions).
For example, these statements specify three sample times: one for continuous
behavior and two for discrete behavior.
ssSetSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
ssSetSampleTime(S, 1, 0.75);
ssSetSampleTime(S, 2, 1.0);
In the mdlUpdate function, the following statement encapsulates the code that
defines the behavior for the sample time of 0.75 second.
if (ssIsSampleHit(S, 1, tid)) {
}
The second argument, 1, corresponds to the second sample time, 0.75 second.
Example of Defining a Sample Time for a Continuous Block
This example defines a sample time for a block that is continuous.
/* Initialize the sample time and offset. */
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
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7 Implementing Block Features
7-24
ssSetOffsetTime(S, 0, 0.0);
}
You must add this statement to the mdlInitializeSizes function.
ssSetNumSampleTimes(S, 1);
Example of Defining a Sample Time for a Hybrid Block
This example defines sample times for a hybrid S-Function block.
/* Initialize the sample time and offset. */
static void mdlInitializeSampleTimes(SimStruct *S)
{
/* Continuous state sample time and offset. */
ssSetSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
ssSetOffsetTime(S, 0, 0.0);
/* Discrete state sample time and offset. */
ssSetSampleTime(S, 1, 0.1);
ssSetOffsetTime(S, 1, 0.025);
}
In the second sample time, the offset causes Simulink to call the mdlUpdate
function at these times: 0.025 second, 0.125 second, 0.225 second, and so on, in
increments of 0.1 second.
The following statement, which indicates how many sample times are defined,
also appears in the mdlInitializeSizes function.
ssSetNumSampleTimes(S, 2);
Synchronizing Multirate S-Function Blocks
If tasks running at different rates need to share data, you must ensure that
data generated by one task is valid when accessed by another task running at
a different rate. You can use the ssIsSpecialSampleHit macro in the
mdlUpdate or mdlOutputs routine of a multirate S-function to ensure that the
shared data is valid. This macro returns true if a sample hit has occurred at
one rate and a sample hit has also occurred at another rate in the same time
step. It thus permits a higher rate task to provide data needed by a slower rate
task at a rate the slower task can accommodate.
Sample Times
Suppose, for example, that your model has an input port operating at one rate,
0, and an output port operating at a slower rate, 1. Further, suppose that you
want the output port to output the value currently on the input. The following
example illustrates usage of this macro.
if (ssISampleHit(S, 0, tid) {
if (ssIsSpecialSampleHit(S, 0, 1, tid) {
/* Transfer input to output memory. */
...
}
}
if (ssIsSampleHit(S, 1, tid) {
/* Emit output. */
...
}
In this example, the first block runs when a sample hit occurs at the input rate.
If the hit also occurs at the output rate, the block transfers the input to the
output memory. The second block runs when a sample hit occurs at the output
rate. It transfers the output in its memory area to the block’s output.
Note that higher-rate tasks always run before slower-rate tasks. Thus, the
input task in the preceding example always runs before the output task,
ensuring that valid data is always present at the output port.
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7 Implementing Block Features
7-26
Work Vectors
If your S-function needs persistent memory storage, use S-function work
vectors instead of static or global variables. If you use static or global variables,
they are used by multiple instances of your S-function. This occurs when you
have multiple S-Function blocks in a Simulink model and the same S-function
C MEX-file has been specified. The ability to keep track of multiple instances
of an S-function is called reentrancy.
You can create an S-function that is reentrant by using work vectors. These are
persistent storage locations that Simulink manages for an S-function. Integer,
floating-point (real), pointer, and general data types are supported. The
number of elements in each vector can be specified dynamically as a function
of the number of inputs to the S-function.
Work vectors have several advantages:
Instance-specific storage for block variables
Integer, real, pointer, and general data types
Elimination of static and global variables and the associated multiple
instance problems
For example, suppose you’d like to track the previous value of each input signal
element entering input port 1 of your S-function. Either the discrete-state
vector or the real-work vector could be used for this, depending upon whether
the previous value is considered a discrete state (that is, compare the unit delay
and the memory block). If you do not want the previous value to be logged when
states are saved, use the real-work vector, rwork. To do this, in
mdlInitializeSizes specify the length of this vector by using ssSetNumRWork.
Then in either mdlStart or mdlInitializeConditions, initialize the rwork
vector ssGetRWork. In mdlOutputs, you can retrieve the previous inputs by
using ssGetRWork. In mdlUpdate, update the previous value of the rwork vector
by using ssGetInputPortRealSignalPtrs.
Work Vectors
Use the macros in this table to specify the length of the work vectors for each
instance of your S-function in mdlInitializeSizes.
Specify vector widths in mdlInitializeSizes. There are three choices:
0 (the default). This indicates that the vector is not used by your S-function.
A positive nonzero integer. This is the width of the vector that is available
for use by mdlStart, mdlInitializeConditions, and S-function routines
called in the simulation loop.
The DYNAMICALLY_SIZED define. The default behavior for dynamically sized
vectors is to set them to the overall block width. Simulink does this after
propagating line widths and sample times. The block width is the width of
the signal passing through your block. In general this is equal to the output
port width.
If the default behavior of dynamically sized vectors does not meet your needs,
use mdlSetWorkWidths and the macros listed in Table 7-1, Macros Used in
Specifying Vector Widths, to set the sizes of the work vectors explicitly.
mdlSetWorkWidths also allows you to set your work vector lengths as functions
of the block sample time and/or port widths.
Table 7-1: Macros Used in Specifying Vector Widths
Macro Description
ssSetNumContStates Width of the continuous-state vector
ssSetNumDiscStates Width of the discrete-state vector
ssSetNumDWork Width of the data type work vector
ssSetNumRWork Width of the real-work vector
ssSetNumIWork Width of the integer-work vector
ssSetNumPWork Width of the pointer-work vector
ssSetNumModes Width of the mode-work vector
ssSetNumNonsampledZCs Width of the nonsampled zero-crossing
vector
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7 Implementing Block Features
7-28
The continuous states are used when you have a state that needs to be
integrated by one of Simulink’s solvers. When you specify continuous states,
you must return the states’ derivatives in mdlDerivatives. The discrete state
vector is used to maintain state information that changes at fixed intervals.
Typically the discrete state vector is updated in place in mdlUpdate.
The integer, real, and pointer work vectors are storage locations that are not
logged by Simulink during simulations. They maintain persistent data
between calls to your S-function.
Work Vectors and Zero Crossings
The mode-work vector and the nonsampled zero-crossing vector are typically
used with zero crossings. Elements of the mode vector are integer values. You
specify the number of mode-vector elements in mdlInitializeSizes, using
ssSetNumModes(S,num). You can then access the mode vector using
ssGetModeVector. The mode vector is used to determine how the mdlOutputs
routine should operate when the solvers are homing in on zero crossings. The
zero crossings or state events (i.e., discontinuities in the first derivatives) of
some signal, usually a function of an input to your S-function, are tracked by
the solver by looking at the nonsampled zero crossings. To register nonsampled
zero crossings, set the number of nonsampled zero crossings in
mdlInitializeSizes, using ssSetNumNonsampledZCs(S, num). Then define
the mdlZeroCrossings routine to return the nonsampled zero crossings. See
matlabroot/simulink/src/sfun_zc.c for an example.
Example Involving a Pointer Work Vector
This example opens a file and stores the FILE pointer in the pointer-work
vector.
The following statement, included in the mdlInitializeSizes function,
indicates that the pointer-work vector is to contain one element.
ssSetNumPWork(S, 1) /* pointer-work vector */
The following code uses the pointer-work vector to store a FILE pointer,
returned from the standard I/O function fopen.
#define MDL_START /* Change to #undef to remove function. */
#if defined(MDL_START)
static void mdlStart(real_T *x0, SimStruct *S)
Work Vectors
{
FILE *fPtr;
void **PWork = ssGetPWork(S);
fPtr = fopen("file.data", "r");
PWork[0] = fPtr;
}
#endif /* MDL_START */
This code retrieves the FILE pointer from the pointer-work vector and passes it
to fclose to close the file.
static void mdlTerminate(SimStruct *S)
{
if (ssGetPWork(S) != NULL) {
FILE *fPtr;
fPtr = (FILE *) ssGetPWorkValue(S,0);
if (fPtr != NULL) {
fclose(fPtr);
}
ssSetPWorkValue(S,0,NULL);
}
}
Note If you are using mdlSetWorkWidths, any work vectors you use in your
S-function should be set to DYNAMICALLY_SIZED in mdlInitializeSizes, even
if the exact value is known before mdlInitializeSizes is called. The size to
be used by the S-function should be specified in mdlSetWorkWidths.
The synopsis is
#define MDL_SET_WORK_WIDTHS /* Change to #undef to remove function. */
#if defined(MDL_SET_WORK_WIDTHS) && defined(MATLAB_MEX_FILE)
static void mdlSetWorkWidths(SimStruct *S)
{
}
#endif /* MDL_SET_WORK_WIDTHS */
For an example, see matlabroot/simulink/src/sfun_dynsize.c.
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7 Implementing Block Features
7-30
Memory Allocation
When you are creating an S-function, the available work vectors might not
provide enough capability. In this case, you need to allocate memory for each
instance of your S-function. The standard MATLAB API memory allocation
routines mxCalloc and mxFree should not be used with C MEX S-functions,
because these routines are designed to be used with MEX-files that are called
from MATLAB and not Simulink. The correct approach for allocating memory
is to use the stdlib.h library routines calloc and free. In mdlStart, allocate
and initialize the memory and place the pointer to it either in pointer-work
vector elements
ssGetPWork(S)[i] = ptr;
or attach it as user data.
ssSetUserData(S,ptr);
In mdlTerminate, free the allocated memory.
Function-Call Subsystems
Function-Call Subsystems
You can create a triggered subsystem whose execution is determined by logic
internal to an S-function instead of by the value of a signal. A subsystem so
configured is called a function-call subsystem. To implement a function-call
subsystem:
In the Trigger block, select function-call as the Trigger type parameter.
In the S-function, use the ssCallSystemWithTid macro to call the triggered
subsystem.
In the model, connect the S-Function block output directly to the trigger port.
Note Function-call connections can only be performed on the first output
port.
Function-call subsystems are not executed directly by Simulink; rather, the
S-function determines when to execute the subsystem. When the subsystem
completes execution, control returns to the S-function. This figure illustrates
the interaction between a function-call subsystem and an S-function.
In this figure, ssCallSystemWithTid executes the function-call subsystem that
is connected to the first output port element. ssCallSystemWithTid returns 0
if an error occurs while executing the function-call subsystem or if the output
is unconnected. After the function-call subsystem executes, control is returned
to your S-function.
Function-call subsystems can only be connected to S-functions that have been
properly configured to accept them.
f()
Function-call
subsystem
void mdlOutputs(SimStruct *S, int_T tid)
{
...
if (!ssCallSystemWithTid(S,outputElement,tid)) {
return; /* error or output is unconnected */
}
<next statement>
...
}
7-31
7 Implementing Block Features
7-32
To configure an S-function to call a function-call subsystem:
1 Specify the elements that are to execute the function-call system in
mdlInitializeSampleTimes. For example:
ssSetCallSystemOutput(S,0); /* call on 1st element */
ssSetCallSystemOutput(S,2); /* call on 3rd element */
2 Execute the subsystem in the appropriate mdlOutputs or mdlUpdate
S-function routine. For example:
static void mdlOutputs(...)
{
if (((int)*uPtrs[0]) % 2 == 1) {
if (!ssCallSystemWithTid(S,0,tid)) {
/* Error occurred, which will be reported by Simulink */
return;
}
} else {
if (!ssCallSystemWithTid(S,2,tid)) {
/* Error occurred, which will be reported by Simulink */
return;
}
}
...
}
See simulink/src/sfun_fcncall.c for an example.
Function-call subsystems are a powerful modeling construct. You can configure
Stateflow? blocks to execute function-call subsystems, thereby extending the
capabilities of the blocks. For more information on their use in Stateflow, see
the Stateflow documentation.
Handling Errors
Handling Errors
When working with S-functions, it is important to handle unexpected events
such as invalid parameter values correctly.
If your S-function has parameters whose contents you need to validate, use the
following technique to report errors encountered.
ssSetErrorStatus(S,"error encountered due to ...");
return;
Note that the second argument to ssSetErrorStatus must be persistent
memory. It cannot be a local variable in your procedure. For example, the
following causes unpredictable errors.
mdlOutputs()
{
char msg[256]; /* ILLEGAL: should be "static char msg[256];" */
sprintf(msg,"Error due to %s", string);
ssSetErrorStatus(S,msg);
return;
}
The ssSetErrorStatus error-handling approach is the suggested alternative to
using the mexErrMsgTxt function. The function mexErrMsgTxt uses exception
handling to immediately terminate S-function execution and return control to
Simulink. In order to support exception handling inside S-functions, Simulink
must set up exception handlers prior to each S-function invocation. This
introduces overhead into simulation.
Exception Free Code
You can avoid this overhead by ensuring that your S-function contains entirely
exception free code. Exception free code refers to code that never long-jumps.
Your S-function is not exception free if it contains any routine that, when
called, has the potential of long-jumping. For example, mexErrMsgTxt throws
an exception (i.e., long-jumps) when called, thus ending execution of your
S-function. Using mxCalloc can cause unpredictable results in the event of a
memory allocation error, because mxCalloc long-jumps. If memory allocation is
needed, use the stdlib.h calloc routine directly and perform your own error
handling.
7-33
7 Implementing Block Features
7-34
If you do not call mexErrMsgTxt or other API routines that cause exceptions, use
the SS_OPTION_EXCEPTION_FREE_CODE S-function option. You do this by issuing
the following command in the mdlInitializeSizes function.
ssSetOptions(S, SS_OPTION_EXCEPTION_FREE_CODE);
Setting this option increases the performance of your S-function by allowing
Simulink to bypass the exception-handling setup that is usually performed
prior to each S-function invocation. You must take extreme care to verify that
your code is exception free when using SS_OPTION_EXCEPTION_FREE_CODE. If
your S-function generates an exception when this option is set, unpredictable
results occur.
All mex* routines have the potential of long-jumping. Several mx* routines also
have the potential of long-jumping. To avoid any difficulties, use only the API
routines that retrieve a pointer or determine the size of parameters. For
example, the following never throw an exception: mxGetPr, mxGetData,
mxGetNumberOfDimensions, mxGetM, mxGetN, and mxGetNumberOfElements.
Code in run-time routines can also throw exceptions. Run-time routines refer
to certain S-function routines that Simulink calls during the simulation loop
(see “How Simulink Interacts with C S-Functions” on page 3-35). The run-time
routines include
mdlGetTimeOfNextVarHit
mdlOutputs
mdlUpdate
mdlDerivatives
If all run-time routines within your S-function are exception free, you can use
this option:
ssSetOptions(S, SS_OPTION_RUNTIME_EXCEPTION_FREE_CODE);
The other routines in your S-function do not have to be exception free.
ssSetErrorStatus Termination Criteria
When you call ssSetErrorStatus and return from your S-function, Simulink
stops the simulation and posts the error. To determine how the simulation
shuts down, refer to the flow chart figure on “How Simulink Interacts with C
S-Functions” on page 3-35. If ssSetErrorStatus is called prior to mdlStart, no
Handling Errors
other S-function routine is called. If ssSetErrorStatus is called in mdlStart or
later, mdlTerminate is called.
Checking Array Bounds
If your S-function causes otherwise inexplicable errors, the reason might be
that the S-function is writing beyond its assigned areas in memory. You can
verify this possibility by enabling Simulink’s array bounds checking feature.
This feature detects any attempt by an S-Function block to write beyond the
areas assigned to it for the following types of block data:
Work vectors (R, I, P, D, and mode)
States (continuous and discrete)
Outputs
To enable array bounds checking, select warning or error from the Bounds
checking options list on the Simulation Parameters dialog box or enter the
following command at the MATLAB command line.
set_param(modelName, 'ArrayBoundsChecking', 'none' | 'warning' |
'error')
7-35
7 Implementing Block Features
7-36
S-Function Examples
Most S-Function blocks require the handling of states, continuous or discrete.
The following sections discuss common types of systems that you can model in
Simulink with S-functions:
Continuous state
Discrete state
Hybrid
Variable step sample time
Zero crossings
Time-varying continuous transfer function
All examples are based on the C MEX-file S-function template
sfuntmpl_basic.c and on sfuntmpl_doc.c, which contains a discussion of the
S-function template.
Example of a Continuous State S-Function
The matlabroot/simulink/src/csfunc.c example shows how to model a
continuous system with states in a C MEX S-function. In continuous state
integration, there is a set of states that Simulink’s solvers integrate using the
following equations.
S-functions that contain continuous states implement a state-space equation.
The output portion is placed in mdlOutputs and the derivative portion in
mdlDerivatives. To visualize how the integration works, refer to the flowchart
in “How Simulink Interacts with C S-Functions” on page 3-35. The output
equation above corresponds to the mdlOutputs in the major time step. Next, the
(output)
(derivative)
yf
0
tx
c
u,,()=
x
·
c
f
d
tx
c
u,,()=
x
c
(states)
uy
(input) (output)
S-Function Examples
example enters the integration section of the flowchart. Here Simulink
performs a number of minor time steps during which it calls mdlOutputs and
mdlDerivatives. Each of these pairs of calls is referred to as an integration
stage. The integration returns with the continuous states updated and the
simulation time moved forward. Time is moved forward as far as possible,
providing that error tolerances in the state are met. The maximum time step
is subject to constraints of discrete events such as the actual simulation stop
time and the user-imposed limit.
Note that csfunc.c specifies that the input port has direct feedthrough. This
is because matrix D is initialized to a nonzero matrix. If D is set equal to a zero
matrix in the state-space representation, the input signal isn’t used in
mdlOutputs. In this case, the direct feedthrough can be set to 0, which indicates
that csfunc.c does not require the input signal when executing mdlOutputs.
7-37
7 Implementing Block Features
7-38
matlabroot/simulink/src/csfunc.c
/* File : csfunc.c
* Abstract:
*
* Example C-file S-function for defining a continuous system.
*
* x' = Ax + Bu
* y = Cx + Du
*
* For more details about S-functions, see simulink/src/sfuntmpl_doc.c.
*
* Copyright 1990-2000 The MathWorks, Inc.
*/
#define S_FUNCTION_NAME csfunc
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
#define U(element) (*uPtrs[element]) /* Pointer to Input Port0 */
static real_T A[2][2]={ { -0.09, -0.01 } ,
{ 1 , 0 }
};
static real_T B[2][2]={ { 1 , -7 } ,
{ 0 , -2 }
};
static real_T C[2][2]={ { 0 , 2 } ,
{ 1 , -5 }
};
static real_T D[2][2]={ { -3 , 0 } ,
{ 1 , 0 }
};
/*====================*
* S-function methods *
*====================*/
/* Function: mdlInitializeSizes ===============================================
* Abstract:
* The sizes information is used by Simulink to determine the S-function
* block's characteristics (number of inputs, outputs, states, etc.).
*/
static void mdlInitializeSizes(SimStruct *S)
{
ssSetNumSFcnParams(S, 0); /* Number of expected parameters */
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
return; /* Parameter mismatch will be reported by Simulink */
}
S-Function Examples
ssSetNumContStates(S, 2);
ssSetNumDiscStates(S, 0);
if (!ssSetNumInputPorts(S, 1)) return;
ssSetInputPortWidth(S, 0, 2);
ssSetInputPortDirectFeedThrough(S, 0, 1);
if (!ssSetNumOutputPorts(S, 1)) return;
ssSetOutputPortWidth(S, 0, 2);
ssSetNumSampleTimes(S, 1);
ssSetNumRWork(S, 0);
ssSetNumIWork(S, 0);
ssSetNumPWork(S, 0);
ssSetNumModes(S, 0);
ssSetNumNonsampledZCs(S, 0);
/* Take care when specifying exception free code - see sfuntmpl_doc.c */
ssSetOptions(S, SS_OPTION_EXCEPTION_FREE_CODE);
}
/* Function: mdlInitializeSampleTimes =========================================
* Abstract:
* Specifiy that we have a continuous sample time.
*/
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
ssSetOffsetTime(S, 0, 0.0);
}
#define MDL_INITIALIZE_CONDITIONS
/* Function: mdlInitializeConditions ========================================
* Abstract:
* Initialize both continuous states to zero.
*/
static void mdlInitializeConditions(SimStruct *S)
{
real_T *x0 = ssGetContStates(S);
int_T lp;
for (lp=0;lp<2;lp++) {
*x0++=0.0;
}
}
7-39
7 Implementing Block Features
7-40
/* Function: mdlOutputs =======================================================
* Abstract:
* y = Cx + Du
*/
static void mdlOutputs(SimStruct *S, int_T tid)
{
real_T *y = ssGetOutputPortRealSignal(S,0);
real_T *x = ssGetContStates(S);
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
UNUSED_ARG(tid); /* not used in single tasking mode */
/* y=Cx+Du */
y[0]=C[0][0]*x[0]+C[0][1]*x[1]+D[0][0]*U(0)+D[0][1]*U(1);
y[1]=C[1][0]*x[0]+C[1][1]*x[1]+D[1][0]*U(0)+D[1][1]*U(1);
}
#define MDL_DERIVATIVES
/* Function: mdlDerivatives =================================================
* Abstract:
* xdot = Ax + Bu
*/
static void mdlDerivatives(SimStruct *S)
{
real_T *dx = ssGetdX(S);
real_T *x = ssGetContStates(S);
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
/* xdot=Ax+Bu */
dx[0]=A[0][0]*x[0]+A[0][1]*x[1]+B[0][0]*U(0)+B[0][1]*U(1);
dx[1]=A[1][0]*x[0]+A[1][1]*x[1]+B[1][0]*U(0)+B[1][1]*U(1);
}
/* Function: mdlTerminate =====================================================
* Abstract:
* No termination needed, but we are required to have this routine.
*/
static void mdlTerminate(SimStruct *S)
{
UNUSED_ARG(S); /* unused input argument */
}
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration function */
#endif
S-Function Examples
Example of a Discrete State S-Function
The matlabroot/simulink/src/dsfunc.c example shows how to model a
discrete system in a C MEX S-function. Discrete systems can be modeled by the
following set of equations.
dsfunc.c implements a discrete state-space equation. The output portion is
placed in mdlOutputs and the update portion in mdlUpdate. To visualize how
the simulation works, refer to the flowchart in “How Simulink Interacts with
C S-Functions” on page 3-35. The output equation above corresponds to the
mdlOutputs in the major time step. The preceding update equation corresponds
to the mdlUpdate in the major time step. If your model does not contain
continuous elements, the integration phase is skipped and time is moved
forward to the next discrete sample hit.
(Output)
(Update)
yf
0
tx
d
u,,()=
x
d 1+
f
u
tx
d
u,,()=
x
d
(states)
uy
(Input) (Output)
7-41
7 Implementing Block Features
7-42
matlabroot/simulink/src/dsfunc.c
/* File : dsfunc.c
* Abstract:
*
* Example C-file S-function for defining a discrete system.
*
* x(n+1) = Ax(n) + Bu(n)
* y(n) = Cx(n) + Du(n)
*
* For more details about S-functions, see simulink/src/sfuntmpl_doc.c.
*
* Copyright 1990-2000 The MathWorks, Inc.
*/
#define S_FUNCTION_NAME dsfunc
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
#define U(element) (*uPtrs[element]) /* Pointer to Input Port0 */
static real_T A[2][2]={ { -1.3839, -0.5097 } ,
{ 1 , 0 }
};
static real_T B[2][2]={ { -2.5559, 0 } ,
{ 0 , 4.2382 }
};
static real_T C[2][2]={ { 0 , 2.0761 } ,
{ 0 , 7.7891 }
};
static real_T D[2][2]={ { -0.8141, -2.9334 } ,
{ 1.2426, 0 }
};
/*====================*
* S-function methods *
*====================*/
/* Function: mdlInitializeSizes ===============================================
* Abstract:
* The sizes information is used by Simulink to determine the S-function
* block's characteristics (number of inputs, outputs, states, etc.).
*/
static void mdlInitializeSizes(SimStruct *S)
{
ssSetNumSFcnParams(S, 0); /* Number of expected parameters */
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
return; /* Parameter mismatch will be reported by Simulink */
S-Function Examples
}
ssSetNumContStates(S, 0);
ssSetNumDiscStates(S, 2);
if (!ssSetNumInputPorts(S, 1)) return;
ssSetInputPortWidth(S, 0, 2);
ssSetInputPortDirectFeedThrough(S, 0, 1);
if (!ssSetNumOutputPorts(S, 1)) return;
ssSetOutputPortWidth(S, 0, 2);
ssSetNumSampleTimes(S, 1);
ssSetNumRWork(S, 0);
ssSetNumIWork(S, 0);
ssSetNumPWork(S, 0);
ssSetNumModes(S, 0);
ssSetNumNonsampledZCs(S, 0);
/* Take care when specifying exception free code - see sfuntmpl_doc.c */
ssSetOptions(S, SS_OPTION_EXCEPTION_FREE_CODE);
}
/* Function: mdlInitializeSampleTimes =========================================
* Abstract:
* Specifiy that we inherit our sample time from the driving block.
*/
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, 1.0);
ssSetOffsetTime(S, 0, 0.0);
}
#define MDL_INITIALIZE_CONDITIONS
/* Function: mdlInitializeConditions ========================================
* Abstract:
* Initialize both discrete states to one.
*/
static void mdlInitializeConditions(SimStruct *S)
{
real_T *x0 = ssGetRealDiscStates(S);
int_T lp;
for (lp=0;lp<2;lp++) {
*x0++=1.0;
}
}
7-43
7 Implementing Block Features
7-44
/* Function: mdlOutputs =======================================================
* Abstract:
* y = Cx + Du
*/
static void mdlOutputs(SimStruct *S, int_T tid)
{
real_T *y = ssGetOutputPortRealSignal(S,0);
real_T *x = ssGetRealDiscStates(S);
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
UNUSED_ARG(tid); /* not used in single tasking mode */
/* y=Cx+Du */
y[0]=C[0][0]*x[0]+C[0][1]*x[1]+D[0][0]*U(0)+D[0][1]*U(1);
y[1]=C[1][0]*x[0]+C[1][1]*x[1]+D[1][0]*U(0)+D[1][1]*U(1);
}
#define MDL_UPDATE
/* Function: mdlUpdate ======================================================
* Abstract:
* xdot = Ax + Bu
*/
static void mdlUpdate(SimStruct *S, int_T tid)
{
real_T tempX[2] = {0.0, 0.0};
real_T *x = ssGetRealDiscStates(S);
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
UNUSED_ARG(tid); /* not used in single tasking mode */
/* xdot=Ax+Bu */
tempX[0]=A[0][0]*x[0]+A[0][1]*x[1]+B[0][0]*U(0)+B[0][1]*U(1);
tempX[1]=A[1][0]*x[0]+A[1][1]*x[1]+B[1][0]*U(0)+B[1][1]*U(1);
x[0]=tempX[0];
x[1]=tempX[1];
}
/* Function: mdlTerminate =====================================================
* Abstract:
* No termination needed, but we are required to have this routine.
*/
static void mdlTerminate(SimStruct *S)
{
UNUSED_ARG(S); /* unused input argument */
}
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
S-Function Examples
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration function */
#endif
Example of a Hybrid System S-Function
The S-function matlabroot/simulink/src/mixedm.c is an example of a hybrid
(a combination of continuous and discrete states) system. mixedm.c combines
elements of csfunc.c and dsfunc.c. If you have a hybrid system, place your
continuous equations in mdlDerivatives and your discrete equations in
mdlUpdate. In addition, you need to check for sample hits to determine at what
point your S-function is being called.
In Simulink block diagram form, the S-function mixedm.c looks like
which implements a continuous integrator followed by a discrete unit delay.
Because there are no tasks to complete at termination, mdlTerminate is an
empty function. mdlDerivatives calculates the derivatives of the continuous
states of the state vector, x, and mdlUpdate contains the equations used to
update the discrete state vector, x.
7-45
7 Implementing Block Features
7-46
matlabroot/simulink/src/mixedm.c
/* File : mixedm.c
* Abstract:
*
* An example S-function illustrating multiple sample times by implementing
* integrator -> ZOH(Ts=1second) -> UnitDelay(Ts=1second)
* with an initial condition of 1.
* (e.g. an integrator followed by unit delay operation).
*
* For more details about S-functions, see simulink/src/sfuntmpl_doc.c
*
* Copyright 1990-2000 The MathWorks, Inc.
*/
#define S_FUNCTION_NAME mixedm
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
#define U(element) (*uPtrs[element]) /* Pointer to Input Port0 */
/*====================*
* S-function methods *
*====================*/
/* Function: mdlInitializeSizes ===============================================
* Abstract:
* The sizes information is used by Simulink to determine the S-function
* block's characteristics (number of inputs, outputs, states, etc.).
*/
static void mdlInitializeSizes(SimStruct *S)
{
ssSetNumSFcnParams(S, 0); /* Number of expected parameters */
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
return; /* Parameter mismatch will be reported by Simulink */
}
ssSetNumContStates(S, 1);
ssSetNumDiscStates(S, 1);
ssSetNumRWork(S, 1); /* for zoh output feeding the delay operator */
if (!ssSetNumInputPorts(S, 1)) return;
ssSetInputPortWidth(S, 0, 1);
ssSetInputPortDirectFeedThrough(S, 0, 1);
ssSetInputPortSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
ssSetInputPortOffsetTime(S, 0, 0.0);
if (!ssSetNumOutputPorts(S, 1)) return;
ssSetOutputPortWidth(S, 0, 1);
ssSetOutputPortSampleTime(S, 0, 1.0);
ssSetOutputPortOffsetTime(S, 0, 0.0);
S-Function Examples
ssSetNumSampleTimes(S, 2);
/* Take care when specifying exception free code - see sfuntmpl_doc.c. */
ssSetOptions(S, (SS_OPTION_EXCEPTION_FREE_CODE |
SS_OPTION_PORT_SAMPLE_TIMES_ASSIGNED));
} /* end mdlInitializeSizes */
/* Function: mdlInitializeSampleTimes =========================================
* Abstract:
* Two tasks: One continuous, one with discrete sample time of 1.0.
*/
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
ssSetOffsetTime(S, 0, 0.0);
ssSetSampleTime(S, 1, 1.0);
ssSetOffsetTime(S, 1, 0.0);
} /* end mdlInitializeSampleTimes */
#define MDL_INITIALIZE_CONDITIONS
/* Function: mdlInitializeConditions ==========================================
* Abstract:
* Initialize both continuous states to one.
*/
static void mdlInitializeConditions(SimStruct *S)
{
real_T *xC0 = ssGetContStates(S);
real_T *xD0 = ssGetRealDiscStates(S);
xC0[0] = 1.0;
xD0[0] = 1.0;
} /* end mdlInitializeConditions */
/* Function: mdlOutputs =======================================================
* Abstract:
* y = xD, and update the zoh internal output.
*/
static void mdlOutputs(SimStruct *S, int_T tid)
{
/* update the internal "zoh" output */
if (ssIsContinuousTask(S, tid)) {
if (ssIsSpecialSampleHit(S, 1, 0, tid)) {
7-47
real_T *zoh = ssGetRWork(S);
7 Implementing Block Features
7-48
real_T *xC = ssGetContStates(S);
*zoh = *xC;
}
}
/* y=xD */
if (ssIsSampleHit(S, 1, tid)) {
real_T *y = ssGetOutputPortRealSignal(S,0);
real_T *xD = ssGetRealDiscStates(S);
y[0]=xD[0];
}
} /* end mdlOutputs */
#define MDL_UPDATE
/* Function: mdlUpdate ======================================================
* Abstract:
* xD = xC
*/
static void mdlUpdate(SimStruct *S, int_T tid)
{
UNUSED_ARG(tid); /* not used in single tasking mode */
/* xD=xC */
if (ssIsSampleHit(S, 1, tid)) {
real_T *xD = ssGetRealDiscStates(S);
real_T *zoh = ssGetRWork(S);
xD[0]=*zoh;
}
} /* end mdlUpdate */
#define MDL_DERIVATIVES
/* Function: mdlDerivatives =================================================
* Abstract:
* xdot = U
*/
static void mdlDerivatives(SimStruct *S)
{
real_T *dx = ssGetdX(S);
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
/* xdot=U */
dx[0]=U(0);
} /* end mdlDerivatives */
S-Function Examples
/* Function: mdlTerminate =====================================================
* Abstract:
* No termination needed, but we are required to have this routine.
*/
static void mdlTerminate(SimStruct *S)
{
UNUSED_ARG(S); /* unused input argument */
}
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration function */
#endif
Example of a Variable-Step S-Function
The example S-function vsfunc.c uses a variable-step sample time. Variable
step-size functions require a call to mdlGetTimeOfNextVarHit, which is an
S-function routine that calculates the time of the next sample hit. S-functions
that use the variable-step sample time can only be used with variable-step
solvers. vsfunc is a discrete S-function that delays its first input by an amount
of time determined by the second input.
The output of vsfunc is simply the input u delayed by a variable amount of
time. mdlOutputs sets the output y equal to state x. mdlUpdate sets the state
vector x equal to u, the input vector. This example calls
mdlGetTimeOfNextVarHit, an S-function routine that calculates and sets the
time of the next hit, that is, the time when vsfunc is next called. In
mdlGetTimeOfNextVarHit, the macro ssGetU is used to get a pointer to the
input u. Then this call is made.
ssSetTNext(S, ssGetT(S)(*u[1]));
The macro ssGetT gets the simulation time t. The second input to the block,
(*u[1]), is added to t, and the macro ssSetTNext sets the time of the next hit
equal to t+(*u[1]), delaying the output by the amount of time set in (*u[1]).
matlabroot/simulink/src/vsfunc.c
/* File : vsfunc.c
* Abstract:
*
* Example C-file S-function for defining a continuous system.
*
7-49
* Variable step S-function example.
7 Implementing Block Features
7-50
* This example S-function illustrates how to create a variable step
* block in Simulink. This block implements a variable step delay
* in which the first input is delayed by an amount of time determined
* by the second input:
*
* dt = u(2)
* y(t+dt) = u(t)
*
* For more details about S-functions, see simulink/src/sfuntmpl_doc.c.
*
* Copyright 1990-2000 The MathWorks, Inc.
*/
#define S_FUNCTION_NAME vsfunc
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
#define U(element) (*uPtrs[element]) /* Pointer to Input Port0 */
/* Function: mdlInitializeSizes ===============================================
* Abstract:
* The sizes information is used by Simulink to determine the S-function
* block's characteristics (number of inputs, outputs, states, etc.).
*/
static void mdlInitializeSizes(SimStruct *S)
{
ssSetNumSFcnParams(S, 0); /* Number of expected parameters */
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
return; /* Parameter mismatch will be reported by Simulink */
}
ssSetNumContStates(S, 0);
ssSetNumDiscStates(S, 1);
if (!ssSetNumInputPorts(S, 1)) return;
ssSetInputPortWidth(S, 0, 2);
ssSetInputPortDirectFeedThrough(S, 0, 1);
if (!ssSetNumOutputPorts(S, 1)) return;
ssSetOutputPortWidth(S, 0, 1);
ssSetNumSampleTimes(S, 1);
ssSetNumRWork(S, 0);
ssSetNumIWork(S, 0);
ssSetNumPWork(S, 0);
ssSetNumModes(S, 0);
ssSetNumNonsampledZCs(S, 0);
if (ssGetSimMode(S) == SS_SIMMODE_RTWGEN && !ssIsVariableStepSolver(S)) {
ssSetErrorStatus(S, "S-function vsfunc.c cannot be used with RTW "
S-Function Examples
"and Fixed-Step Solvers because it contains variable"
" sample time");
}
/* Take care when specifying exception free code - see sfuntmpl_doc.c */
ssSetOptions(S, SS_OPTION_EXCEPTION_FREE_CODE);
}
/* Function: mdlInitializeSampleTimes =========================================
* Abstract:
* Variable-Step S-function
*/
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, VARIABLE_SAMPLE_TIME);
ssSetOffsetTime(S, 0, 0.0);
}
#define MDL_INITIALIZE_CONDITIONS
/* Function: mdlInitializeConditions ========================================
* Abstract:
* Initialize discrete state to zero.
*/
static void mdlInitializeConditions(SimStruct *S)
{
real_T *x0 = ssGetRealDiscStates(S);
x0[0] = 0.0;
}
#define MDL_GET_TIME_OF_NEXT_VAR_HIT
static void mdlGetTimeOfNextVarHit(SimStruct *S)
{
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
/* Make sure input will increase time */
if (U(1) <= 0.0) {
/* If not, abort simulation */
ssSetErrorStatus(S,"Variable step control input must be "
"greater than zero");
return;
}
ssSetTNext(S, ssGetT(S)+U(1));
}
7-51
7 Implementing Block Features
7-52
/* Function: mdlOutputs =======================================================
* Abstract:
* y = x
*/
static void mdlOutputs(SimStruct *S, int_T tid)
{
real_T *y = ssGetOutputPortRealSignal(S,0);
real_T *x = ssGetRealDiscStates(S);
/* Return the current state as the output */
y[0] = x[0];
}
#define MDL_UPDATE
/* Function: mdlUpdate ========================================================
* Abstract:
* This function is called once for every major integration time step.
* Discrete states are typically updated here, but this function is useful
* for performing any tasks that should only take place once per integration
* step.
*/
static void mdlUpdate(SimStruct *S, int_T tid)
{
real_T *x = ssGetRealDiscStates(S);
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
x[0]=U(0);
}
/* Function: mdlTerminate =====================================================
* Abstract:
* No termination needed, but we are required to have this routine.
*/
static void mdlTerminate(SimStruct *S)
{
}
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration function */
#endif
Example of a Zero Crossing S-Function
The example S-function sfun_zc_sat demonstrates how to implement a
Saturation block. This S-function is designed to work with either fixed- or
S-Function Examples
variable-step solvers. When this S-function inherits a continuous sample
time and a variable-step solver is being used, a zero-crossings algorithm is
used to locate the exact points at which the saturation occurs.
matlabroot/simulink/src/sfun_zc_sat.c
/* File : sfun_zc_sat.c
* Abstract:
*
* Example of an S-function which has nonsampled zero crossings to
* implement a saturation function. This S-function is designed to be
* used with a variable or fixed step solver.
*
* A saturation is described by three equations
*
* (1) y = UpperLimit
* (2) y = u
* (3) y = LowerLimit
*
* and a set of inequalities that specify which equation to use
*
* if UpperLimit < u then use (1)
* if LowerLimit <= u <= UpperLimit then use (2)
* if u < LowerLimit then use (3)
*
* A key fact is that the valid equation 1, 2, or 3, can change at
* any instant. Nonsampled zero crossing support helps the variable step
* solvers locate the exact instants when behavior switches from one equation
* to another.
*
* Copyright 1990-2000 The MathWorks, Inc.
*/
#define S_FUNCTION_NAME sfun_zc_sat
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
/*========================*
* General Defines/macros *
*========================*/
/* index to Upper Limit */
#define I_PAR_UPPER_LIMIT 0
/* index to Lower Limit */
#define I_PAR_LOWER_LIMIT 1
/* total number of block parameters */
#define N_PAR 2
7-53
7 Implementing Block Features
7-54
/*
* Make access to mxArray pointers for parameters more readable.
*/
#define P_PAR_UPPER_LIMIT ( ssGetSFcnParam(S,I_PAR_UPPER_LIMIT) )
#define P_PAR_LOWER_LIMIT ( ssGetSFcnParam(S,I_PAR_LOWER_LIMIT) )
#define MDL_CHECK_PARAMETERS
#if defined(MDL_CHECK_PARAMETERS) && defined(MATLAB_MEX_FILE)
/* Function: mdlCheckParameters =============================================
* Abstract:
* Check that parameter choices are allowable.
*/
static void mdlCheckParameters(SimStruct *S)
{
int_T i;
int_T numUpperLimit;
int_T numLowerLimit;
const char *msg = NULL;
/*
* check parameter basics
*/
for ( i = 0; i < N_PAR; i++ ) {
if ( mxIsEmpty( ssGetSFcnParam(S,i) ) ||
mxIsSparse( ssGetSFcnParam(S,i) ) ||
mxIsComplex( ssGetSFcnParam(S,i) ) ||
!mxIsNumeric( ssGetSFcnParam(S,i) ) ) {
msg = "Parameters must be real vectors.";
goto EXIT_POINT;
}
}
/*
* Check sizes of parameters.
*/
numUpperLimit = mxGetNumberOfElements( P_PAR_UPPER_LIMIT );
numLowerLimit = mxGetNumberOfElements( P_PAR_LOWER_LIMIT );
if ( ( numUpperLimit != 1 ) &&
( numLowerLimit != 1 ) &&
( numUpperLimit != numLowerLimit ) ) {
msg = "Number of input and output values must be equal.";
goto EXIT_POINT;
}
/*
* Error exit point
*/
EXIT_POINT:
if (msg != NULL) {
S-Function Examples
ssSetErrorStatus(S, msg);
}
}
#endif /* MDL_CHECK_PARAMETERS */
/* Function: mdlInitializeSizes ===============================================
* Abstract:
* Initialize the sizes array.
*/
static void mdlInitializeSizes(SimStruct *S)
{
int_T numUpperLimit, numLowerLimit, maxNumLimit;
/*
* Set and Check parameter count
*/
ssSetNumSFcnParams(S, N_PAR);
#if defined(MATLAB_MEX_FILE)
if (ssGetNumSFcnParams(S) == ssGetSFcnParamsCount(S)) {
mdlCheckParameters(S);
if (ssGetErrorStatus(S) != NULL) {
return;
}
} else {
return; /* Parameter mismatch will be reported by Simulink */
}
#endif
/*
* Get parameter size info.
*/
numUpperLimit = mxGetNumberOfElements( P_PAR_UPPER_LIMIT );
numLowerLimit = mxGetNumberOfElements( P_PAR_LOWER_LIMIT );
if (numUpperLimit > numLowerLimit) {
maxNumLimit = numUpperLimit;
} else {
maxNumLimit = numLowerLimit;
}
/*
* states
*/
ssSetNumContStates(S, 0);
ssSetNumDiscStates(S, 0);
/*
* outputs
* The upper and lower limits are scalar expanded
7-55
* so their size determines the size of the output
7 Implementing Block Features
7-56
* only if at least one of them is not scalar.
*/
if (!ssSetNumOutputPorts(S, 1)) return;
if ( maxNumLimit > 1 ) {
ssSetOutputPortWidth(S, 0, maxNumLimit);
} else {
ssSetOutputPortWidth(S, 0, DYNAMICALLY_SIZED);
}
/*
* inputs
* If the upper or lower limits are not scalar then
* the input is set to the same size. However, the
* ssSetOptions below allows the actual width to
* be reduced to 1 if needed for scalar expansion.
*/
if (!ssSetNumInputPorts(S, 1)) return;
ssSetInputPortDirectFeedThrough(S, 0, 1 );
if ( maxNumLimit > 1 ) {
ssSetInputPortWidth(S, 0, maxNumLimit);
} else {
ssSetInputPortWidth(S, 0, DYNAMICALLY_SIZED);
}
/*
* sample times
*/
ssSetNumSampleTimes(S, 1);
/*
* work
*/
ssSetNumRWork(S, 0);
ssSetNumIWork(S, 0);
ssSetNumPWork(S, 0);
/*
* Modes and zero crossings:
* If we have a variable-step solver and this block has a continuous
* sample time, then
* o One mode element will be needed for each scalar output
* in order to specify which equation is valid (1), (2), or (3).
* o Two ZC elements will be needed for each scalar output
* in order to help the solver find the exact instants
* at which either of the two possible "equation switches"
* One will be for the switch from eq. (1) to (2);
* the other will be for eq. (2) to (3) and vice versa.
* otherwise
* o No modes and nonsampled zero crossings will be used.
S-Function Examples
*
*/
ssSetNumModes(S, DYNAMICALLY_SIZED);
ssSetNumNonsampledZCs(S, DYNAMICALLY_SIZED);
/*
* options
* o No mexFunctions and no problematic mxFunctions are called
* so the exception free code option safely gives faster simulations.
* o Scalar expansion of the inputs is desired. The option provides
* this without the need to write mdlSetOutputPortWidth and
* mdlSetInputPortWidth functions.
*/
ssSetOptions(S, ( SS_OPTION_EXCEPTION_FREE_CODE |
SS_OPTION_ALLOW_INPUT_SCALAR_EXPANSION));
} /* end mdlInitializeSizes */
/* Function: mdlInitializeSampleTimes =========================================
* Abstract:
* Specify that the block is continuous.
*/
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, INHERITED_SAMPLE_TIME);
ssSetOffsetTime(S, 0, 0);
}
#define MDL_SET_WORK_WIDTHS
#if defined(MDL_SET_WORK_WIDTHS) && defined(MATLAB_MEX_FILE)
/* Function: mdlSetWorkWidths ===============================================
* The width of the Modes and the ZCs depends on the width of the output.
* This width is not always known in mdlInitializeSizes so it is handled
* here.
*/
static void mdlSetWorkWidths(SimStruct *S)
{
int nModes;
int nNonsampledZCs;
if (ssIsVariableStepSolver(S) &&
ssGetSampleTime(S,0) == CONTINUOUS_SAMPLE_TIME &&
ssGetOffsetTime(S,0) == 0.0) {
int numOutput = ssGetOutputPortWidth(S, 0);
/*
* modes and zero crossings
7-57
* o One mode element will be needed for each scalar output
7 Implementing Block Features
7-58
* in order to specify which equation is valid (1), (2), or (3).
* o Two ZC elements will be needed for each scalar output
* in order to help the solver find the exact instants
* at which either of the two possible "equation switches"
* One will be for the switch from eq. (1) to (2);
* the other will be for eq. (2) to (3) and vice versa.
*/
nModes = numOutput;
nNonsampledZCs = 2 * numOutput;
} else {
nModes = 0;
nNonsampledZCs = 0;
}
ssSetNumModes(S,nModes);
ssSetNumNonsampledZCs(S,nNonsampledZCs);
}
#endif /* MDL_SET_WORK_WIDTHS */
/* Function: mdlOutputs =======================================================
* Abstract:
*
* A saturation is described by three equations
*
* (1) y = UpperLimit
* (2) y = u
* (3) y = LowerLimit
*
* When this block is used with a fixed-step solver or it has a noncontinuous
* sample time, the equations are used as it
*
* Now consider the case of this block being used with a variable-step solver
* and it has a continusous sample time. Solvers work best on smooth problems.
* In order for the solver to work without chattering, limit cycles, or
* similar problems, it is absolutely crucial that the same equation be used
* throughout the duration of a MajorTimeStep. To visualize this, consider
* the case of the Saturation block feeding an Integrator block.
*
* To implement this rule, the mode vector is used to specify the
* valid equation based on the following:
*
* if UpperLimit < u then use (1)
* if LowerLimit <= u <= UpperLimit then use (2)
* if u < LowerLimit then use (3)
*
* The mode vector is changed only at the beginning of a MajorTimeStep.
*
* During a minor time step, the equation specified by the mode vector
* is used without question. Most of the time, the value of u will agree
* with the equation specified by the mode vector. However, sometimes u's
* value will indicate a different equation. Nonetheless, the equation
* specified by the mode vector must be used.
S-Function Examples
*
* When the mode and u indicate different equations, the corresponding
* calculations are not correct. However, this is not a problem. From
* the ZC function, the solver will know that an equation switch occurred
* in the middle of the last MajorTimeStep. The calculations for that
* time step will be discarded. The ZC function will help the solver
* find the exact instant at which the switch occurred. Using this knowledge,
* the length of the MajorTimeStep will be reduced so that only one equation
* is valid throughout the entire time step.
*/
static void mdlOutputs(SimStruct *S, int_T tid)
{
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
real_T *y = ssGetOutputPortRealSignal(S,0);
int_T numOutput = ssGetOutputPortWidth(S,0);
int_T iOutput;
/*
* Set index and increment for input signal, upper limit, and lower limit
* parameters so that each gives scalar expansion if needed.
*/
int_T uIdx = 0;
int_T uInc = ( ssGetInputPortWidth(S,0) > 1 );
const real_T *upperLimit = mxGetPr( P_PAR_UPPER_LIMIT );
int_T upperLimitInc = ( mxGetNumberOfElements( P_PAR_UPPER_LIMIT ) > 1 );
const real_T *lowerLimit = mxGetPr( P_PAR_LOWER_LIMIT );
int_T lowerLimitInc = ( mxGetNumberOfElements( P_PAR_LOWER_LIMIT ) > 1 );
UNUSED_ARG(tid); /* not used in single tasking mode */
if (ssGetNumNonsampledZCs(S) == 0) {
/*
* This block is being used with a fixed-step solver or it has
* a noncontinuous sample time, so we always saturate.
*/
for (iOutput = 0; iOutput < numOutput; iOutput++) {
if (*uPtrs[uIdx] >= *upperLimit) {
*y++ = *upperLimit;
} else if (*uPtrs[uIdx] > *lowerLimit) {
*y++ = *uPtrs[uIdx];
} else {
*y++ = *lowerLimit;
}
upperLimit += upperLimitInc;
lowerLimit += lowerLimitInc;
uIdx += uInc;
}
} else {
/*
* This block is being used with a variable-step solver.
7-59
*/
7 Implementing Block Features
7-60
int_T *mode = ssGetModeVector(S);
/*
* Specify indices for each equation.
*/
enum { UpperLimitEquation, NonLimitEquation, LowerLimitEquation };
/*
* Update the Mode Vector ONLY at the beginning of a MajorTimeStep
*/
if ( ssIsMajorTimeStep(S) ) {
/*
* Specify the mode, ie the valid equation for each output scalar.
*/
for ( iOutput = 0; iOutput < numOutput; iOutput++ ) {
if ( *uPtrs[uIdx] > *upperLimit ) {
/*
* Upper limit eq is valid.
*/
mode[iOutput] = UpperLimitEquation;
} else if ( *uPtrs[uIdx] < *lowerLimit ) {
/*
* Lower limit eq is valid.
*/
mode[iOutput] = LowerLimitEquation;
} else {
/*
* Nonlimit eq is valid.
*/
mode[iOutput] = NonLimitEquation;
}
/*
* Adjust indices to give scalar expansion if needed.
*/
uIdx += uInc;
upperLimit += upperLimitInc;
lowerLimit += lowerLimitInc;
}
/*
* Reset index to input and limits.
*/
uIdx = 0;
upperLimit = mxGetPr( P_PAR_UPPER_LIMIT );
lowerLimit = mxGetPr( P_PAR_LOWER_LIMIT );
} /* end IsMajorTimeStep */
/*
* For both MinorTimeSteps and MajorTimeSteps calculate each scalar
* output using the equation specified by the mode vector.
*/
for ( iOutput = 0; iOutput < numOutput; iOutput++ ) {
S-Function Examples
if ( mode[iOutput] == UpperLimitEquation ) {
/*
* Upper limit eq.
*/
*y++ = *upperLimit;
} else if ( mode[iOutput] == LowerLimitEquation ) {
/*
* Lower limit eq.
*/
*y++ = *lowerLimit;
} else {
/*
* Nonlimit eq.
*/
*y++ = *uPtrs[uIdx];
}
/*
* Adjust indices to give scalar expansion if needed.
*/
uIdx += uInc;
upperLimit += upperLimitInc;
lowerLimit += lowerLimitInc;
}
}
} /* end mdlOutputs */
#define MDL_ZERO_CROSSINGS
#if defined(MDL_ZERO_CROSSINGS) && (defined(MATLAB_MEX_FILE) || defined(NRT))
/* Function: mdlZeroCrossings =================================================
* Abstract:
* This will only be called if the number of nonsampled zero crossings is
* greater than 0 which means this block has a continuous sample time and the
* model is using a variable-step solver.
*
* Calculate zero crossing (ZC) signals that help the solver find the
* exact instants at which equation switches occur:
*
* if UpperLimit < u then use (1)
* if LowerLimit <= u <= UpperLimit then use (2)
* if u < LowerLimit then use (3)
*
* The key words are help find. There is no choice of a function that will
* direct the solver to the exact instant of the change. The solver will
* track the zero crossing signal and do a bisection style search for the
* exact instant of equation switch.
*
* There is generally one ZC signal for each pair of signals that can
* switch. The three equations above would break into two pairs (1)&(2)
7-61
* and (2)&(3). The possibility of a "long jump" from (1) to (3) does
7 Implementing Block Features
7-62
* not need to be handled as a separate case. It is implicitly handled.
*
* When ZCs are calculated, the value is normally used twice. When it is
* first calculated, it is used as the end of the current time step. Later,
* it will be used as the beginning of the following step.
*
* The sign of the ZC signal always indicates an equation from the pair. For
* S-functions, which equation is associated with a positive ZC and which is
* associated with a negative ZC doesn't really matter. If the ZC is positive
* at the beginning and at the end of the time step, this implies that the
* "positive" equation was valid throughout the time step. Likewise, if the
* ZC is negative at the beginning and at the end of the time step, this
* implies that the "negative" equation was valid throughout the time step.
* Like any other nonlinear solver, this is not foolproof, but it is an
* excellent indicator. If the ZC has a different sign at the beginning and
* at the end of the time step, then a equation switch definitely occurred
* during the time step.
*
* Ideally, the ZC signal gives an estimate of when an equation switch
* occurred. For example, if the ZC signal is -2 at the beginning and +6 at
* the end, then this suggests that the switch occurred
* 25% = 100%*(-2)/(-2-(+6)) of the way into the time step. It will almost
* never be true that 25% is perfectly correct. There is no perfect choice
* for a ZC signal, but there are some good rules. First, choose the ZC
* signal to be continuous. Second, choose the ZC signal to give a monotonic
* measure of the "distance" to a signal switch; strictly monotonic is ideal.
*/
static void mdlZeroCrossings(SimStruct *S)
{
int_T iOutput;
int_T numOutput = ssGetOutputPortWidth(S,0);
real_T *zcSignals = ssGetNonsampledZCs(S);
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
/*
* Set index and increment for the input signal, upper limit, and lower
* limit parameters so that each gives scalar expansion if needed.
*/
int_T uIdx = 0;
int_T uInc = ( ssGetInputPortWidth(S,0) > 1 );
real_T *upperLimit = mxGetPr( P_PAR_UPPER_LIMIT );
int_T upperLimitInc = ( mxGetNumberOfElements( P_PAR_UPPER_LIMIT ) > 1 );
real_T *lowerLimit = mxGetPr( P_PAR_LOWER_LIMIT );
int_T lowerLimitInc = ( mxGetNumberOfElements( P_PAR_LOWER_LIMIT ) > 1 );
/*
* For each output scalar, give the solver a measure of "how close things
* are" to an equation switch.
*/
for ( iOutput = 0; iOutput < numOutput; iOutput++ ) {
/* The switch from eq (1) to eq (2)
*
S-Function Examples
* if UpperLimit < u then use (1)
* if LowerLimit <= u <= UpperLimit then use (2)
*
* is related to how close u is to UpperLimit. A ZC choice
* that is continuous, strictly monotonic, and is
* u - UpperLimit
* or it is negative.
*/
zcSignals[2*iOutput] = *uPtrs[uIdx] - *upperLimit;
/* The switch from eq (2) to eq (3)
*
* if LowerLimit <= u <= UpperLimit then use (2)
* if u < LowerLimit then use (3)
*
* is related to how close u is to LowerLimit. A ZC choice
* that is continuous, strictly monotonic, and is
* u - LowerLimit.
*/
zcSignals[2*iOutput+1] = *uPtrs[uIdx] - *lowerLimit;
/*
* Adjust indices to give scalar expansion if needed.
*/
uIdx += uInc;
upperLimit += upperLimitInc;
lowerLimit += lowerLimitInc;
}
}
#endif /* end mdlZeroCrossings */
/* Function: mdlTerminate =====================================================
* Abstract:
* No termination needed, but we are required to have this routine.
*/
static void mdlTerminate(SimStruct *S)
{
UNUSED_ARG(S); /* unused input argument */
}
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration function */
#endif
7-63
7 Implementing Block Features
7-64
Example of a Time-Varying Continuous Transfer
Function
The S-function stvctf is an example of a time-varying continuous transfer
function. It demonstrates how to work with the solvers so that the simulation
maintains consistency, which means that the block maintains smooth and
consistent signals for the integrators although the equations that are being
integrated are changing.
matlabroot/simulink/src/stvctf.c
/*
* File : stvctf.c
* Abstract:
* Time Varying Continuous Transfer Function block
*
* This S-function implements a continuous time transfer function
* whose transfer function polynomials are passed in via the input
* vector. This is useful for continuous time adaptive control
* applications.
*
* This S-function is also an example of how to use banks to avoid
* problems with computing derivatives when a continuous output has
* discontinuities. The consistency checker can be used to verify that
* your S-function is correct with respect to always maintaining smooth
* and consistent signals for the integrators. By consistent we mean that
* two mdlOutputs calls at major time t and minor time t are always the
* same. The consistency checker is enabled on the diagnostics page of the
* simulation parameters dialog box. The update method of this S-function
* modifies the coefficients of the transfer function, which cause the
* output to "jump." To have the simulation work properly, we need to let
* the solver know of these discontinuities by setting
* ssSetSolverNeedsReset and then we need to use multiple banks of
* coefficients so the coefficients used in the major time step output
* and the minor time step outputs are the same. In the simulation loop
* we have:
* Loop:
* o Output in major time step at time t
* o Update in major time step at time t
* o Integrate (minor time step):
* o Consistency check: recompute outputs at time t and compare
* with current outputs.
* o Derivatives at time t
* o One or more Output,Derivative evaluations at time t+k
* where k <= step_size to be taken.
* o Compute state, x
* o t = t + step_size
* End_Integrate
* End_Loop
* Another purpose of the consistency checker is to verify that when
S-Function Examples
* the solver needs to try a smaller step_size, the recomputing of
* the output and derivatives at time t doesn't change. Step size
* reduction occurs when tolerances aren't met for the current step size.
* The ideal ordering would be to update after integrate. To achieve
* this we have two banks of coefficients. And the use of the new
* coefficients, which were computed in update, is delayed until after
* the integrate phase is complete.
*
* This block has multiple sample times and will not work correctly
* in a multitasking environment. It is designed to be used in
* a single tasking (or variable step) simulation environment.
* Because this block accesses the input signal in both tasks,
* it cannot specify the sample times of the input and output ports
* (SS_OPTION_PORT_SAMPLE_TIMES_ASSIGNED).
*
* See simulink/src/sfuntmpl_doc.c.
*
* Copyright 1990-2000 The MathWorks, Inc.
*/
#define S_FUNCTION_NAME stvctf
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
/*
* Defines for easy access to the numerator and denominator polynomials
* parameters
*/
#define NUM(S) ssGetSFcnParam(S, 0)
#define DEN(S) ssGetSFcnParam(S, 1)
#define TS(S) ssGetSFcnParam(S, 2)
#define NPARAMS 3
#define MDL_CHECK_PARAMETERS
#if defined(MDL_CHECK_PARAMETERS) && defined(MATLAB_MEX_FILE)
/* Function: mdlCheckParameters =============================================
* Abstract:
* Validate our parameters to verify:
* o The numerator must be of a lower order than the denominator.
* o The sample time must be a real positive nonzero value.
*/
static void mdlCheckParameters(SimStruct *S)
{
int_T i;
for (i = 0; i < NPARAMS; i++) {
real_T *pr;
int_T el;
int_T nEls;
if (mxIsEmpty( ssGetSFcnParam(S,i)) ||
7-65
mxIsSparse( ssGetSFcnParam(S,i)) ||
7 Implementing Block Features
7-66
mxIsComplex( ssGetSFcnParam(S,i)) ||
!mxIsNumeric( ssGetSFcnParam(S,i)) ) {
ssSetErrorStatus(S,"Parameters must be real finite vectors");
return;
}
pr = mxGetPr(ssGetSFcnParam(S,i));
nEls = mxGetNumberOfElements(ssGetSFcnParam(S,i));
for (el = 0; el < nEls; el++) {
if (!mxIsFinite(pr[el])) {
ssSetErrorStatus(S,"Parameters must be real finite vectors");
return;
}
}
}
if (mxGetNumberOfElements(NUM(S)) > mxGetNumberOfElements(DEN(S)) &&
mxGetNumberOfElements(DEN(S)) > 0 && *mxGetPr(DEN(S)) != 0.0) {
ssSetErrorStatus(S,"The denominator must be of higher order than "
"the numerator, nonempty and with first "
"element nonzero");
return;
}
/* xxx verify finite */
if (mxGetNumberOfElements(TS(S)) != 1 || mxGetPr(TS(S))[0] <= 0.0) {
ssSetErrorStatus(S,"Invalid sample time specified");
return;
}
}
#endif /* MDL_CHECK_PARAMETERS */
/* Function: mdlInitializeSizes ===============================================
* Abstract:
* The sizes information is used by Simulink to determine the S-function
* block's characteristics (number of inputs, outputs, states, etc.).
*/
static void mdlInitializeSizes(SimStruct *S)
{
int_T nContStates;
int_T nCoeffs;
/* See sfuntmpl_doc.c for more details on the macros below. */
ssSetNumSFcnParams(S, NPARAMS); /* Number of expected parameters. */
#if defined(MATLAB_MEX_FILE)
if (ssGetNumSFcnParams(S) == ssGetSFcnParamsCount(S)) {
mdlCheckParameters(S);
if (ssGetErrorStatus(S) != NULL) {
return;
}
} else {
return; /* Parameter mismatch will be reported by Simulink. */
S-Function Examples
}
#endif
/*
* Define the characteristics of the block:
*
* Number of continuous states: length of denominator - 1
* Inputs port width 2 * (NumContStates+1) + 1
* Output port width 1
* DirectFeedThrough: 0 (Although this should be computed.
* We'll assume coefficients entered
* are strictly proper).
* Number of sample times: 2 (continuous and discrete)
* Number of Real work elements: 4*NumCoeffs
* (Two banks for num and den coeff's:
* NumBank0Coeffs
* DenBank0Coeffs
* NumBank1Coeffs
* DenBank1Coeffs)
* Number of Integer work elements: 2 (indicator of active bank 0 or 1
* and flag to indicate when banks
* have been updated).
*
* The number of inputs arises from the following:
* o 1 input (u)
* o the numerator and denominator polynomials each have NumContStates+1
* coefficients
*/
nCoeffs = mxGetNumberOfElements(DEN(S));
nContStates = nCoeffs - 1;
ssSetNumContStates(S, nContStates);
ssSetNumDiscStates(S, 0);
if (!ssSetNumInputPorts(S, 1)) return;
ssSetInputPortWidth(S, 0, 1 + (2*nCoeffs));
ssSetInputPortDirectFeedThrough(S, 0, 0);
ssSetInputPortSampleTime(S, 0, mxGetPr(TS(S))[0]);
ssSetInputPortOffsetTime(S, 0, 0);
if (!ssSetNumOutputPorts(S,1)) return;
ssSetOutputPortWidth(S, 0, 1);
ssSetOutputPortSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
ssSetOutputPortOffsetTime(S, 0, 0);
ssSetNumSampleTimes(S, 2);
ssSetNumRWork(S, 4 * nCoeffs);
ssSetNumIWork(S, 2);
ssSetNumPWork(S, 0);
7-67
ssSetNumModes(S, 0);
7 Implementing Block Features
7-68
ssSetNumNonsampledZCs(S, 0);
/* Take care when specifying exception free code - see sfuntmpl_doc.c */
ssSetOptions(S, (SS_OPTION_EXCEPTION_FREE_CODE));
} /* end mdlInitializeSizes */
/* Function: mdlInitializeSampleTimes =========================================
* Abstract:
* This function is used to specify the sample time(s) for the
* S-function. This S-function has two sample times. The
* first, a continous sample time, is used for the input to the
* transfer function, u. The second, a discrete sample time
* provided by the user, defines the rate at which the transfer
* function coefficients are updated.
*/
static void mdlInitializeSampleTimes(SimStruct *S)
{
/*
* the first sample time, continuous
*/
ssSetSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
ssSetOffsetTime(S, 0, 0.0);
/*
* the second, discrete sample time, is user provided
*/
ssSetSampleTime(S, 1, mxGetPr(TS(S))[0]);
ssSetOffsetTime(S, 1, 0.0);
} /* end mdlInitializeSampleTimes */
#define MDL_INITIALIZE_CONDITIONS
/* Function: mdlInitializeConditions ==========================================
* Abstract:
* Initalize the states, numerator and denominator coefficients.
*/
static void mdlInitializeConditions(SimStruct *S)
{
int_T i;
int_T nContStates = ssGetNumContStates(S);
real_T *x0 = ssGetContStates(S);
int_T nCoeffs = nContStates + 1;
real_T *numBank0 = ssGetRWork(S);
real_T *denBank0 = numBank0 + nCoeffs;
int_T *activeBank = ssGetIWork(S);
/*
* The continuous states are all initialized to zero.
S-Function Examples
*/
for (i = 0; i < nContStates; i++) {
x0[i] = 0.0;
numBank0[i] = 0.0;
denBank0[i] = 0.0;
}
numBank0[nContStates] = 0.0;
denBank0[nContStates] = 0.0;
/*
* Set up the initial numerator and denominator.
*/
{
const real_T *numParam = mxGetPr(NUM(S));
int numParamLen = mxGetNumberOfElements(NUM(S));
const real_T *denParam = mxGetPr(DEN(S));
int denParamLen = mxGetNumberOfElements(DEN(S));
real_T den0 = denParam[0];
for (i = 0; i < denParamLen; i++) {
denBank0[i] = denParam[i] / den0;
}
for (i = 0; i < numParamLen; i++) {
numBank0[i] = numParam[i] / den0;
}
}
/*
* Normalize if this transfer function has direct feedthrough.
*/
for (i = 1; i < nCoeffs; i++) {
numBank0[i] -= denBank0[i]*numBank0[0];
}
/*
* Indicate bank0 is active (i.e. bank1 is oldest).
*/
*activeBank = 0;
} /* end mdlInitializeConditions */
/* Function: mdlOutputs =======================================================
* Abstract:
* The outputs for this block are computed by using a controllable state-
* space representation of the transfer function.
*/
static void mdlOutputs(SimStruct *S, int_T tid)
{
7-69
if (ssIsContinuousTask(S,tid)) {
7 Implementing Block Features
7-70
int i;
real_T *num;
int nContStates = ssGetNumContStates(S);
real_T *x = ssGetContStates(S);
int_T nCoeffs = nContStates + 1;
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
real_T *y = ssGetOutputPortRealSignal(S,0);
int_T *activeBank = ssGetIWork(S);
/*
* Switch banks because we've updated them in mdlUpdate and we're no
* longer in a minor time step.
*/
if (ssIsMajorTimeStep(S)) {
int_T *banksUpdated = ssGetIWork(S) + 1;
if (*banksUpdated) {
*activeBank = !(*activeBank);
*banksUpdated = 0;
/*
* Need to tell the solvers that the derivatives are no
* longer valid.
*/
ssSetSolverNeedsReset(S);
}
}
num = ssGetRWork(S) + (*activeBank) * (2*nCoeffs);
/*
* The continuous system is evaluated using a controllable state space
* representation of the transfer function. This implies that the
* output of the system is equal to:
*
* y(t) = Cx(t) + Du(t)
* = [ b1 b2 ... bn]x(t) + b0u(t)
*
* where b0, b1, b2, ... are the coefficients of the numerator
* polynomial:
*
* B(s) = b0 s^n + b1 s^n-1 + b2 s^n-2 + ... + bn-1 s + bn
*/
*y = *num++ * (*uPtrs[0]);
for (i = 0; i < nContStates; i++) {
*y += *num++ * *x++;
}
}
} /* end mdlOutputs */
#define MDL_UPDATE
/* Function: mdlUpdate ========================================================
* Abstract:
* Every time through the simulation loop, update the
S-Function Examples
* transfer function coefficients. Here we update the oldest bank.
*/
static void mdlUpdate(SimStruct *S, int_T tid)
{
UNUSED_ARG(tid); /* not used in single tasking mode */
if (ssIsSampleHit(S, 1, tid)) {
int_T i;
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
int_T uIdx = 1;/*1st coeff is after signal input*/
int_T nContStates = ssGetNumContStates(S);
int_T nCoeffs = nContStates + 1;
int_T bankToUpdate = !ssGetIWork(S)[0];
real_T *num = ssGetRWork(S)+bankToUpdate*2*nCoeffs;
real_T *den = num + nCoeffs;
real_T den0;
int_T allZero;
/*
* Get the first denominator coefficient. It will be used
* for normalizing the numerator and denominator coefficients.
*
* If all inputs are zero, we probably could have unconnected
* inputs, so use the parameter as the first denominator coefficient.
*/
den0 = *uPtrs[uIdx+nCoeffs];
if (den0 == 0.0) {
den0 = mxGetPr(DEN(S))[0];
}
/*
* Grab the numerator.
*/
allZero = 1;
for (i = 0; (i < nCoeffs) && allZero; i++) {
allZero &= *uPtrs[uIdx+i] == 0.0;
}
if (allZero) { /* if numerator is all zero */
const real_T *numParam = mxGetPr(NUM(S));
int_T numParamLen = mxGetNumberOfElements(NUM(S));
/*
* Move the input to the denominator input and
* get the denominator from the input parameter.
*/
uIdx += nCoeffs;
num += nCoeffs - numParamLen;
for (i = 0; i < numParamLen; i++) {
*num++ = *numParam++ / den0;
}
7-71
} else {
7 Implementing Block Features
7-72
for (i = 0; i < nCoeffs; i++) {
*num++ = *uPtrs[uIdx++] / den0;
}
}
/*
* Grab the denominator.
*/
allZero = 1;
for (i = 0; (i < nCoeffs) && allZero; i++) {
allZero &= *uPtrs[uIdx+i] == 0.0;
}
if (allZero) { /* If denominator is all zero. */
const real_T *denParam = mxGetPr(DEN(S));
int_T denParamLen = mxGetNumberOfElements(DEN(S));
den0 = denParam[0];
for (i = 0; i < denParamLen; i++) {
*den++ = *denParam++ / den0;
}
} else {
for (i = 0; i < nCoeffs; i++) {
*den++ = *uPtrs[uIdx++] / den0;
}
}
/*
* Normalize if this transfer function has direct feedthrough.
*/
num = ssGetRWork(S) + bankToUpdate*2*nCoeffs;
den = num + nCoeffs;
for (i = 1; i < nCoeffs; i++) {
num[i] -= den[i]*num[0];
}
/*
* Indicate oldest bank has been updated.
*/
ssGetIWork(S)[1] = 1;
}
} /* end mdlUpdate */
#define MDL_DERIVATIVES
/* Function: mdlDerivatives ===================================================
* Abstract:
* The derivatives for this block are computed by using a controllable
* state-space representation of the transfer function.
*/
static void mdlDerivatives(SimStruct *S)
S-Function Examples
{
int_T i;
int_T nContStates = ssGetNumContStates(S);
real_T *x = ssGetContStates(S);
real_T *dx = ssGetdX(S);
int_T nCoeffs = nContStates + 1;
int_T activeBank = ssGetIWork(S)[0];
const real_T *num = ssGetRWork(S) + activeBank*(2*nCoeffs);
const real_T *den = num + nCoeffs;
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
/*
* The continuous system is evaluated using a controllable state-space
* representation of the transfer function. This implies that the
* next continuous states are computed using:
*
* dx = Ax(t) + Bu(t)
* = [-a1 -a2 ... -an] [x1(t)] + [u(t)]
* [ 1 0 ... 0] [x2(t)] + [0]
* [ 0 1 ... 0] [x3(t)] + [0]
* [ . . ... .] . + .
* [ . . ... .] . + .
* [ . . ... .] . + .
* [ 0 0 ... 1 0] [xn(t)] + [0]
*
* where a1, a2, ... are the coefficients of the numerator polynomial:
*
* A(s) = s^n + a1 s^n-1 + a2 s^n-2 + ... + an-1 s + an
*/
dx[0] = -den[1] * x[0] + *uPtrs[0];
for (i = 1; i < nContStates; i++) {
dx[i] = x[i-1];
dx[0] -= den[i+1] * x[i];
}
} /* end mdlDerivatives */
/* Function: mdlTerminate =====================================================
* Abstract:
* Called when the simulation is terminated.
* For this block, there are no end of simulation tasks.
*/
static void mdlTerminate(SimStruct *S)
{
UNUSED_ARG(S); /* unused input argument */
} /* end mdlTerminate */
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
7-73
#else
7 Implementing Block Features
7-74
#include "cg_sfun.h" /* Code generation registration function */
#endif
8
Writing S-Functions for
Real-Time Workshop
The following sections explain how to write S-functions that work with the Real-Time Workshop.
Introduction (p. 8-2) Describes various approaches to writing S-functions for
the Real-Time Workshop.
Noninlined S-Functions (p. 8-7) Explains the noninlined approach to writing S-functions
for the Real-Time Workshop.
Writing Wrapper S-Functions (p. 8-9) Creating S-functions that serve as wrappers for existing
code.
Fully Inlined S-Functions (p. 8-19) Explains the inlined approach to writing S-functions for
the Real-Time Workshop.
Fully Inlined S-Function with the
mdlRTW Routine (p. 8-21)
How to use the mdlRTW callback method in an inlined
S-function.
Creating Code-Reuse-Compatible
S-Functions (p. 8-42)
How to create S-functions that are compatible with the
Real-Time Workshop’s subsystem code reuse feature.
8 Writing S-Functions for Real-Time Workshop
8-2
Introduction
This chapter describes how to create S-functions that work seamlessly with the
Real-Time Workshop. It begins with basic concepts and concludes with an
example of how to create a highly optimized direct-index lookup table
S-Function block.
This chapter assumes that you understand these concepts:
Level 2 S-functions
Target Language Compiler (TLC)
The basics of how the Real-Time Workshop creates generated code
See the Target Language Compiler Reference Guide and the Real-Time
Workshop User’s Guide for more information about these subjects.
A note on terminology: when this chapter refers to actions performed by the
Target Language Compiler, including parsing, caching, creating buffers, etc.,
the name Target Language Compiler is spelled out fully. When referring to
code written in the Target Language Compiler syntax, this chapter uses the
abbreviation TLC.
Note The guidelines presented in this chapter are for Real-Time Workshop
users. Even if you do not currently use the Real-Time Workshop, we
recommend that you follow the guidelines presented in this chapter when
writing S-functions, especially if you are creating general-purpose S-functions.
Classes of Problems Solved by S-Functions
S-functions help solve various kinds of problems you might face when working
with Simulink and the Real-Time Workshop (Real-Time Workshop). These
problems include
Extending the set of algorithms (blocks) provided by Simulink and
Real-Time Workshop
Interfacing legacy (hand-written) C-code with Simulink and Real-Time
Workshop
Generating highly optimized C-code for embedded systems
Introduction
S-functions and S-function routines form an application program interface
(API) that allows you to implement generic algorithms in the Simulink
environment with a great deal of flexibility. This flexibility cannot always be
maintained when you use S-functions with the Real-Time Workshop. For
example, it is not possible to access the MATLAB workspace from an S-function
that is used with the Real-Time Workshop. However, using the techniques
presented in this chapter, you can create S-functions for most applications that
work with the generated code from the Real-Time Workshop.
Although S-functions provide a generic and flexible solution for implementing
complex algorithms in Simulink, they require significant memory and
computation resources. Most often the additional resources are acceptable for
real-time rapid prototyping systems. In many cases, though, additional
resources are unavailable in real-time embedded applications. You can
minimize memory and computational requirements by using the Target
Language Compiler technology provided with the Real-Time Workshop to
inline your S-functions.
Types of S-Functions
The implementation of S-functions changes based on your requirements. This
chapter discusses the typical problems that you may face and how to create
S-functions for applications that need to work with Simulink and the
Real-Time Workshop. These are some (informally defined) common situations:
1 “I’m not concerned with efficiency. I just want to write one version of my
algorithm and have it work in Simulink and the Real-Time Workshop
automatically.”
2 “I have a lot of hand-written code that I need to interface. I want to call my
function from Simulink and the Real-Time Workshop in an efficient
manner.”
or said another way:
“I want to create a block for my blockset that will be distributed throughout
my organization. I’d like it to be very maintainable with efficient code. I’d
like my algorithm to exist in one place but work with both Simulink and the
Real-Time Workshop.”
8-3
8 Writing S-Functions for Real-Time Workshop
8-4
3 “I want to implement a highly optimized algorithm in Simulink and the
Real-Time Workshop that looks like a built-in block and generates very
efficient code.”
The MathWorks has adopted terminology for these different requirements.
Respectively, the situations described above map to this terminology:
1 Noninlined S-function
2 Wrapper S-function
3 Fully inlined S-function
Noninlined S-Functions
A noninlined S-function is a C-MEX S-function that is treated identically by
Simulink and the Real-Time Workshop. In general, you implement your
algorithm once according to the S-function API. Simulink and the Real-Time
Workshop call the S-function routines (e.g., mdlOutputs) at the appropriate
points during model execution.
Significant memory and computation resources are required for each instance
of a noninlined S-Function block. However, this routine of incorporating
algorithms into Simulink and the Real-Time Workshop is typical during the
prototyping phase of a project where efficiency is not important. The advantage
gained by forgoing efficiency is the ability to change model parameters and/or
structures rapidly.
Note that writing a noninlined S-function does not involve any TLC coding.
Noninlined S-functions are the default case for the Real-Time Workshop in the
sense that once you’ve built a C-MEX S-function in your model, there is no
additional preparation prior to clicking Build in the Real-Time Workshop
Page of the Simulation Parameters dialog box for your model.
Wrapper S-Functions
A wrapper S-function is ideal for interfacing hand-written code or a large
algorithm that is encapsulated within a few procedures. In this situation,
usually the procedures reside in modules that are separate from the C-MEX
S-function. The S-function module typically contains a few calls to your
procedures. Because the S-function module does not contain any parts of your
algorithm, but only calls your code, it is referred to as a wrapper S-function.
Introduction
In addition to the C-MEX S-function wrapper, you need to create a TLC
wrapper that complements your S-function. The TLC wrapper is similar to the
S-function wrapper in that it contains calls to your algorithm.
Fully Inlined S-Functions
A fully inlined S-function builds your algorithm (block) into Simulink and the
Real-Time Workshop in a manner that is indistinguishable from a built-in
block. Typically, a fully inlined S-function requires you to implement your
algorithm twice: once for Simulink (C-MEX S-function) and once for the
Real-Time Workshop (TLC file). The complexity of the TLC file depends on the
complexity of your algorithm and the level of efficiency you’re trying to achieve
in the generated code. TLC files vary from simple to complex in structure.
Basic Files Required for Implementation
This section briefly describes what files and functions you’ll need to create
noninlined, wrapper, and fully inlined S-functions.
Noninlined S-functions require the C-MEX S-function source code
sfunction.c.
Wrapper S-functions that inline a call to your algorithm (your C function)
require an sfunction.tlc file.
Fully inlined S-functions require an sfunction.tlc file. Fully inlined
S-functions produce the optimal code for a parameterized S-function. This is
an S-function that operates in a specific mode dependent upon fixed
S-function parameters that do not change during model execution. For a
given operating mode, the sfunction.tlc file specifies the exact code that is
generated to implement the algorithm for that mode. For example, the
direct-index lookup table S-function at the end of this chapter contains two
operating modes — one for evenly spaced x-data and one for unevenly
spaced x-data.
- Fully inlined S-functions might require the placement of the mdlRTW
routine in your S-function MEX-file sfunction.c. The mdlRTW routine lets
you place information in model.rtw, which is the file that is processed by
the Target Language Compiler prior to executing sfunction.tlc when
generating code. This is useful when you want to introduce nontunable
parameters into your TLC file.
8-5
8 Writing S-Functions for Real-Time Workshop
8-6
For S-functions to work correctly in the Simulink environment, a certain
amount of overhead code is necessary. When the Real-Time Workshop
generates code from models that contain S-functions (without sfunction.tlc
files), it embeds some of this overhead code in the generated C code. If you want
to optimize your real-time code and eliminate some of the overhead code, you
must inline (or embed) your S-functions. This involves writing a TLC
(sfunction.tlc) file that directs the Real-Time Workshop to eliminate all
overhead code from the generated code. The Target Language Compiler, which
is part of the Real-Time Workshop, processes sfunction.tlc files to define
how to inline your S-function algorithm in the generated code.
Note The term inline should not be confused with the C++ inline keyword. In
MathWorks terminology, inline means to specify a textual string in place of
the call to the general S-function API routines (e.g., mdlOutputs). For example,
when we say that a TLC file is used to inline an S-function, we mean that the
generated code contains the appropriate C code that would normally appear
within the S-function routines and the S-function itself has been removed
from the build process.
Noninlined S-Functions
Noninlined S-Functions
Noninlined S-functions are identified by the absence of an sfunction.tlc file
for your S-function (sfunction.mex). When placing a noninlined S-function in
a model that is to be used with the Real-Time Workshop, the following
MATLAB API functions are supported:
mxGetEps
mxGetInf
mxGetM
mxGetN
mxGetNaN
mxGetPr — Note that using mxGetPr on an empty matrix does not return
NULL; rather, it returns a random value. Therefore, you should protect calls
to mxGetPr with mxIsEmpty.
mxGetScalar
mxGetString
mxIsEmpty
mxIsFinite
mxIsInf
In addition, parameters to S-functions can only be of type double precision or
characters contained in scalars, vectors, or 2-D matrices. To obtain more
flexibility in the type of parameters you can supply to S-functions or the
operations in the S-function, you need to inline your S-function and (possibly)
use an mdlRTW S-function routine.
S-Function Module Names for Real-Time Workshop
Builds
If your S-function is built with multiple modules, you must provide the build
process names of additional modules. You can do this through the Real-Time
Workshop template makefile technology, or more conveniently by using the
set_param MATLAB command. For example, if your S-function is built with
multiple modules, as in
mex sfun_main.c sfun_module1.c sfun_module2.c
specify the names of the modules without the extension, using the command
8-7
8 Writing S-Functions for Real-Time Workshop
8-8
set_param(sfun_block,'SFunctionModules','sfun_module1 sfun_module2')
The parameter can also be a variable, as in
modules = 'sfun_module1 sfun_module2'
set_param(sfun_block,'SFunctionModules','modules')
or a string to be evaluated (this is needed when the modules are valid
identifiers).
set_param(sfun_block,'SFunctionModules','''sfun_module1 sfun_module2''')
Writing Wrapper S-Functions
Writing Wrapper S-Functions
This section describes how to create S-functions that work seamlessly with
Simulink and the Real-Time Workshop using the wrapper concept. This section
begins by describing how to interface your algorithms in Simulink by writing
MEX S-function wrappers (sfunction.mex). It finishes with a description of
how to direct the Real-Time Workshop to insert your algorithm into the
generated code by creating a TLC S-function wrapper (sfunction.tlc).
MEX S-Function Wrapper
Creating S-functions using an S-function wrapper allows you to insert your C
code algorithms in Simulink and the Real-Time Workshop with little or no
change to your original C code function. A MEX S-function wrapper is an
S-function that calls code that resides in another module. In effect, the wrapper
binds your code to Simulink. A TLC S-function wrapper is a TLC file that
specifies how the Real-Time Workshop should call your code (the same code
that was called from the C-MEX S-function wrapper).
Suppose you have an algorithm (i.e., a C function) called my_alg that resides in
the file my_alg.c. You can integrate my_alg into Simulink by creating a MEX
S-function wrapper (e.g., wrapsfcn.c). Once this is done, Simulink can call
my_alg from an S-Function block. However, the Simulink S-function contains
a set of empty functions that Simulink requires for various API-related
purposes. For example, although only mdlOutputs calls my_alg, Simulink calls
mdlTerminate as well, even though this S-function routine performs no action.
You can integrate my_alg into the Real-Time Workshop generated code (i.e.,
embed the call to my_alg in the generated code) by creating a TLC S-function
wrapper (e.g., wrapsfcn.tlc). The advantage of creating a TLC S-function
wrapper is that the empty function calls can be eliminated and the overhead of
executing the mdlOutputs function and then the my_alg function can be
eliminated.
Wrapper S-functions are useful when you are creating new algorithms that are
procedural in nature or when you are integrating legacy code into Simulink.
However, if you want to create code that is
Interpretive in nature in Simulink (i.e., highly parameterized by operating
modes)
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8 Writing S-Functions for Real-Time Workshop
8-10
Heavily optimized in the Real-Time Workshop (i.e., no extra tests to decide
what mode the code is operating in)
then you must create a fully inlined TLC file for your S-function.
Writing Wrapper S-Functions
This figure illustrates the wrapper S-function concept.
Figure 8-1: How S-Functions Interface with Hand-Written Code
wrapsfcn
wrapsfcn.c
...
mdlOutputs(...)
{
...
my_alg();
}
Simulink
Place the name of your S-function
in the S-Function block’s dialog box.
S-function
mdlOutputs in
wrapsfcn.mex
calls external
function my_alg.
my_alg.c
...
real_T my_alg(real_T u)
{
...
y=f(u);
}
In Simulink, the S-function
calls mdlOutputs, which
in turn calls my_alg.
Real-Time Workshop
wrapper.c, the generated
code, calls mdlOutputs,
which then calls my_alg.
wrapper.mdl
wrapper.c
...
mdlOutputs(...)
{
...
my_alg();
}
In the TLC wrapper
version of the S-function,
mdlOutputs in
wrapper.exe calls
my_alg.
*The dotted line above is the path taken if the S-function does not have a
TLC wrapper file. If there is no TLC wrapper file, the generated code calls
mdlOutputs.
*See note below
8-11
8 Writing S-Functions for Real-Time Workshop
8-12
Using an S-function wrapper to import algorithms in your Simulink model
means that the S-function serves as an interface that calls your C code
algorithms from mdlOutputs. S-function wrappers have the advantage that you
can quickly integrate large stand-alone C code into your model without having
to make changes to the code.
This is an example of a model that includes an S-function wrapper.
Figure 8-1: An Example Model That Includes an S-Function Wrapper
There are two files associated with the wrapsfcn block, the S-function wrapper
and the C code that contains the algorithm. This is the S-function wrapper code
for this example, called wrapsfcn.c.
#define S_FUNCTION_NAME wrapsfcn
#define S_FUNCTION_LEVEL 2
#include "simstruc.h"
extern real_T my_alg(real_T u);
/*
* mdlInitializeSizes - initialize the sizes array
*/
static void mdlInitializeSizes(SimStruct *S)
{
ssSetNumSFcnParams( S, 0); /*number of input arguments*/
if (!ssSetNumInputPorts(S, 1)) return;
ssSetInputPortWidth(S, 0, 1);
ssSetInputPortDirectFeedThrough(S, 0, 1);
if (!ssSetNumOutputPorts(S,1)) return;
ssSetOutputPortWidth(S, 0, 1);
ssSetNumSampleTimes( S, 1);
Declare my_alg as
extern.
}
Writing Wrapper S-Functions
/*
* mdlInitializeSampleTimes - indicate that this S-function runs
* at the rate of the source (driving block)
*/
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, INHERITED_SAMPLE_TIME);
ssSetOffsetTime(S, 0, 0.0);
}
/*
* mdlOutputs - compute the outputs by calling my_alg, which
* resides in another module, my_alg.c
*/
static void mdlOutputs(SimStruct *S, int_T tid)
{
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
real_T *y = ssGetOutputPortRealSignal(S,0);
*y = my_alg(*uPtrs[0]);
}
/*
* mdlTerminate - called when the simulation is terminated.
*/
static void mdlTerminate(SimStruct *S)
{
}
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration function */
#endif
The S-function routine mdlOutputs contains a function call to my_alg, which is
the C function that contains the algorithm that the S-function performs. This
is the code for my_alg.c:
#include "tmwtypes.h"
real_T my_alg(real_T u)
{
return(u * 2.0);
}
The wrapper S-function wrapsfcn calls my_alg, which computes u * 2.0. To
build wrapsfcn.mex, use the following command:
mex wrapsfcn.c my_alg.c
Place the call to
my_alg in
mdlOutputs.
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8 Writing S-Functions for Real-Time Workshop
8-14
TLC S-Function Wrapper
This section describes how to inline the call to my_alg in the mdlOutputs
section of the generated code. In the above example, the call to my_alg is
embedded in the mdlOutputs section as
*y = my_alg(*uPtrs[0]);
When you are creating a TLC S-function wrapper, the goal is to have the
Real-Time Workshop embed the same type of call in the generated code.
It is instructive to look at how the Real-Time Workshop executes S-functions
that are not inlined. A noninlined S-function is identified by the absence of the
file sfunction.tlc and the existence of sfunction.mex. When generating code
for a noninlined S-function, the Real-Time Workshop generates a call to
mdlOutputs through a function pointer that, in this example, then calls my_alg.
The wrapper example contains one S-function, wrapsfcn.mex. You must
compile and link an additional module, my_alg, with the generated code. To do
this, specify
set_param('wrapper/S-Function','SFunctionModules','my_alg')
The code generated when using grt.tlc as the system target file without
wrapsfcn.tlc is
<Generated code comments for wrapper model with noninlined wrapsfcn S-function>
#include <math.h>
#include <string.h>
#include "wrapper.h"
#include "wrapper.prm"
/* Start the model */
void mdlStart(void)
{
/* (no start code required) */
}
/* Compute block outputs */
void mdlOutputs(int_T tid)
{
/* Sin Block: <Root>/Sin */
rtB.Sin = rtP.Sin.Amplitude *
sin(rtP.Sin.Frequency * ssGetT(rtS) + rtP.Sin.Phase);
Writing Wrapper S-Functions
/* Level2 S-Function Block: <Root>/S-Function (wrapsfcn) */
{
SimStruct *rts = ssGetSFunction(rtS, 0);
sfcnOutputs(rts, tid);
}
/* Outport Block: <Root>/Out */
rtY.Out = rtB.S_Function;
}
/* Perform model update */
void mdlUpdate(int_T tid)
{
/* (no update code required) */
}
/* Terminate function */
void mdlTerminate(void)
{
/* Level2 S-Function Block: <Root>/S-Function (wrapsfcn) */
{
SimStruct *rts = ssGetSFunction(rtS, 0);
sfcnTerminate(rts);
}
}
#include "wrapper.reg"
/* [EOF] wrapper.c */
In addition to the overhead outlined above, the wrapper.reg generated file
contains the initialization of the SimStruct for the wrapper S-Function block.
There is one child SimStruct for each S-Function block in your model. You can
significantly reduce this overhead by creating a TLC wrapper for the
S-function.
How to Inline
The generated code makes the call to your S-function, wrapsfcn.c, in
mdlOutputs by using this code:
SimStruct *rts = ssGetSFunction(rtS, 0);
sfcnOutputs(rts, tid);
This call has a significant amount of computational overhead associated with
it. First, Simulink creates a SimStruct data structure for the S-Function block.
Second, the Real-Time Workshop constructs a call through a function pointer
Noninlined
S-functions create a
SimStruct object and
generate a call to the
S-function routine
Noninlined
S-functions require a
SimStruct object and
the call to the
S-function routine
mdlTerminate.
8-15
to execute mdlOutputs, then mdlOutputs calls my_alg. By inlining the call to
8 Writing S-Functions for Real-Time Workshop
8-16
your C algorithm, my_alg, you can eliminate both the SimStruct and the extra
function call, thereby improving the efficiency and reducing the size of the
generated code.
Inlining a wrapper S-function requires an sfunction.tlc file for the
S-function; this file must contain the function call to my_alg. This picture
shows the relationships between the algorithm, the wrapper S-function, and
the sfunction.tlc file.
Figure 8-2: Inlining an Algorithm by Using a TLC File
To inline this call, you have to place your function call in an sfunction.tlc file
with the same name as the S-function (in this example, wrapsfcn.tlc). This
causes the Target Language Compiler to override the default method of placing
calls to your S-function in the generated code.
my_alg.c
myalg()
{
<C code here>
}
wrapper.c
...
mdlOutputs
{
...
y = my_alg();
...
}
...
wrapsfcn.tlc
...
%<y> = my_alg(%<u>);
...
The wrapsfcn.tlc file tells the
Real-Time Workshop how to inline the
call to my_alg using this statement:
Writing Wrapper S-Functions
This is the wrapsfcn.tlc file that inlines wrapsfcn.c.
%% File : wrapsfcn.tlc
%% Abstract:
%% Example inlined tlc file for S-function wrapsfcn.c
%%
%implements "wrapsfcn" "C"
%% Function: BlockTypeSetup ====================================================
%% Abstract:
%% Create function prototype in model.h as:
%% "extern real_T my_alg(real_T u);"
%%
%function BlockTypeSetup(block, system) void
%openfile buffer
extern real_T my_alg(real_T u);
%closefile buffer
%<LibCacheFunctionPrototype(buffer)>
%endfunction %% BlockTypeSetup
%% Function: Outputs ===========================================================
%% Abstract:
%% y = my_alg( u );
%%
%function Outputs(block, system) Output
/* %<Type> Block: %<Name> */
%assign u = LibBlockInputSignal(0, "", "", 0)
%assign y = LibBlockOutputSignal(0, "", "", 0)
%% PROVIDE THE CALLING STATEMENT FOR "algorithm"
%<y> = my_alg(%<u>);
%endfunction %% Outputs
The first section of this code directs the Real-Time Workshop to inline the
wrapsfcn S-Function block and generate the code in C:
%implements "wrapsfcn" "C"
The next task is to tell the Real-Time Workshop that the routine my_alg needs
to be declared external in the generated wrapper.h file for any wrapsfcn
S-Function blocks in the model. You only need to do this once for all wrapsfcn
S-Function blocks, so use the BlockTypeSetup function. In this function, you
tell the Target Language Compiler to create a buffer and cache the my_alg as
extern in the wrapper.h generated header file.
The final step is the inlining of the call to the function my_alg. This is done by
the Outputs function. In this function, you load the input and output and place
a direct call to my_alg. The call is embedded in wrapper.c.
This line is placed in
wrapper.h.
This line is expanded
and placed in
mdlOutputs within
wrapper.c.
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8 Writing S-Functions for Real-Time Workshop
8-18
The Inlined Code
The code generated when you inline your wrapper S-function is similar to the
default generated code. The mdlTerminate function no longer contains a call to
an empty function and the mdlOutputs function now directly calls my_alg.
void mdlOutputs(int_T tid)
{
/* Sin Block: <Root>/Sin */
rtB.Sin = rtP.Sin.Amplitude *
sin(rtP.Sin.Frequency * ssGetT(rtS) + rtP.Sin.Phase);
/* S-Function Block: <Root>/S-Function */
rtB.S_Function = my_alg(rtB.Sin);
/* Outport Block: <Root>/Out */
rtY.Out = rtB.S_Function;
}
In addition, wrapper.reg no longer creates a child SimStruct for the S-function
because the generated code is calling my_alg directly. This eliminates over 1K
of memory usage.
Inlined call to the
function my_alg.
Fully Inlined S-Functions
Fully Inlined S-Functions
Continuing the example of the previous section, you could eliminate the call to
my_alg entirely by specifying the explicit code (i.e., 2.0 * u) in wrapsfcn.tlc.
This is referred to as a fully inlined S-function. While this can improve
performance, if your C code is large this can be a lengthy task. In addition, you
now have to maintain your algorithm in two places, the C S-function itself and
the corresponding TLC file. However, the performance gains might outweigh
the disadvantages. To inline the algorithm used in this example, in the Outputs
section of your wrapsfcn.tlc file, instead of writing
%<y> = my_alg(%<u>);
use
%<y> = 2.0 * %<u>;
This is the code produced in mdlOutputs:
void mdlOutputs(int_T tid)
{
/* Sin Block: <Root>/Sin */
rtB.Sin = rtP.Sin.Amplitude *
sin(rtP.Sin.Frequency * ssGetT(rtS) + rtP.Sin.Phase);
/* S-Function Block: <Root>/S-Function */
rtB.S_Function = 2.0 * rtB.Sin;
/* Outport Block: <Root>/Out */
rtY.Out = rtB.S_Function;
}
The Target Language Compiler has replaced the call to my_alg with the
algorithm itself.
Multiport S-Function Example
A more advanced multiport inlined S-function example exists in
matlabroot/simulink/src/sfun_multiport.c and
matlabroot/toolbox/simulink/blocks/tlc_c/sfun_multiport.tlc. This
S-function demonstrates how to create a fully inlined TLC file for an S-function
This is the explicit
embedding of the
algorithm.
8-19
8 Writing S-Functions for Real-Time Workshop
8-20
that contains multiple ports. You might find that looking at this example aids
in the understanding of fully inlined TLC files.
Fully Inlined S-Function with the mdlRTW Routine
Fully Inlined S-Function with the mdlRTW Routine
You can make a more fully inlined S-function that uses the S-function mdlRTW
routine. The purpose of the mdlRTW routine is to provide the code generation
process with more information about how the S-function is to be inlined,
including
Renaming of tunable parameters in the generated code. This improves
readability of the code by replacing p1, p2, etc., by names of your choice.
Creating a parameter record of a nontunable parameter for use with a TLC
file.
mdlRTW does this by placing information into the model.rtw file. The mdlRTW
routine is described in the text file
matlabroot/simulink/src/sfuntmpl_doc.c.
As an example of how to use the mdlRTW function, this section discusses the
steps you must take to create a direct-index lookup S-function. Lookup tables
are collections of ordered data points of a function. Typically, these tables use
some interpolation scheme to approximate values of the associated function
between known data points. To incorporate the example lookup table algorithm
in Simulink, the first step is to write an S-function that executes the algorithm
in mdlOutputs. To produce the most efficient C code, the next step is to create
a corresponding TLC file to eliminate computational overhead and improve the
performance of the lookup computations.
For your convenience, Simulink provides support for two general purpose
lookup 1-D and 2-D algorithms. You can use these algorithms as they are or
create a custom lookup table S-function to fit your requirements. This section
demonstrates how to create a 1-D lookup S-function, sfun_directlook.c, and
its corresponding inlined sfun_directlook.tlc file. (See the Real-Time
Workshop User’s Guide and the Target Language Compiler Reference Guide for
more details on the Target Language Compiler.) This 1-D direct-index lookup
table example demonstrates the following concepts that you need to know to
create your own custom lookup tables:
Error checking of S-function parameters
Caching of information for the S-function that doesn’t change during model
execution
8-21
8 Writing S-Functions for Real-Time Workshop
8-22
How to use the mdlRTW routine to customize the Real-Time Workshop
generated code to produce the optimal code for a given set of block
parameters
How to generate an inlined TLC file for an S-function in a combination of the
fully inlined form and/or the wrapper form
S-Function RTWdata
There is a property of blocks called RTWdata, which can be used by the Target
Language Compiler when inlining an S-function. RTWdata is a structure of
strings that you can attach to a block. It is saved with the model and placed in
the model.rtw file when generating code. For example, this set of MATLAB
commands,
mydata.field1 = 'information for field1';
mydata.field2 = 'information for field2';
set_param(gcb,'RTWdata',mydata)
get_param(gcb,'RTWdata')
produces this result:
ans =
field1: 'information for field1'
field2: 'information for field2'
Inside the model.rtw file for the associated S-Function block is this
information.
Block {
Type "S-Function"
RTWdata {
field1 "information for field1"
field2 "information for field2"
}
Fully Inlined S-Function with the mdlRTW Routine
The Direct-Index Lookup Table Algorithm
The 1-D lookup table block provided in the Simulink library uses interpolation
or extrapolation when computing outputs. This extra accuracy is not needed in
all situations. In this example, you create a lookup table that directly indexes
the output vector (y-data vector) based on the current input (x-data) point.
This direct 1-D lookup example computes an approximate solution p(x) to a
partially known function f(x) at x=x0, given data point pairs (x,y) in the form of
an x-data vector and a y-data vector. For a given data pair (e.g., the ith pair),
y_i = f(x_i). It is assumed that the x-data values are monotonically increasing.
If x0 is outside the range of the x-data vector, the first or last point is returned.
The parameters to the S-function are
XData, YData, XEvenlySpaced
XData and YData are double vectors of equal length representing the values of
the unknown function. XDataEvenlySpaced is a scalar, 0.0 for false and 1.0 for
true. If the XData vector is evenly spaced, more efficient code is generated.
8-23
8 Writing S-Functions for Real-Time Workshop
8-24
The following graph illustrates how the parameters XData=[1:6]and
YData=[1,2,7,4,5,9] are handled. For example, if the input (x-value) to the
S-Function block is 3, the output (y-value) is 7.
Figure 8-3: Typical Output from a Lookup Table Example
The Direct-Index Lookup Table Example
This section shows how to improve the lookup table by inlining a direct-index
S-function with a TLC file. Note that this direct-index lookup table S-function
doesn’t require a TLC file to work with the Real-Time Workshop. Here the
example uses a TLC file for the direct-index lookup table S-function to reduce
the code size and increase efficiency of the generated code.
Implementation of the direct-index algorithm with inlined TLC file requires
the S-function main module, sfun_directlook.c, and a corresponding
lookup_index.c module. The lookup_index.c module contains the
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
1
2
3
4
5
6
7
8
9
GetDirectLookupIndex routine that is used to locate the index in the XData for
Fully Inlined S-Function with the mdlRTW Routine
the current x input value when the XData is unevenly spaced. The
GetDirectLookupIndex routine is called from both the S-function and the
generated code. Here the example uses the wrapper concept for sharing C code
between Simulink MEX-files and the generated code.
If the XData is evenly spaced, then both the S-function main module and the
generated code contain the lookup algorithm (not a call to the algorithm) to
compute the y-value of a given x-value, because the algorithm is short. This
demonstrates the use of a fully inlined S-function for generating optimal code.
The inlined TLC file, which performs either a wrapper call or embeds the
optimal C code, is sfun_directlook.tlc (see page -39).
Error Handling
In this example, the mdlCheckParameters routine on page -31 verifies that
The new parameter settings are correct.
XData and YData are vectors of the same length containing real finite
numbers.
XDataEvenlySpaced is a scalar.
The XData vector is a monotonically increasing vector and evenly spaced if
needed.
Note that the mdlInitializeSizes routine explicitly calls
mdlCheckParameters after it verifies that the number of parameters passed to
the S-function is correct. After Simulink calls mdlInitializeSizes, it then
calls mdlCheckParameters whenever you change the parameters or there is a
need to reevaluate them.
User Data Caching
The mdlStart routine on page -34 illustrates how to cache information that
does not change during the simulation (or while the generated code is
executing). The example caches the value of the XDataEvenlySpaced parameter
in UserData, a field of the SimStruct. The line
ssSetSFcnParamTunable(S, XDATAEVENLYSPACED_PIDX, 0);
in mdlInitializeSizes tells Simulink to disallow changes to the
XDataEvenlySpaced parameter. During execution, mdlOutputs accesses the
value of XDataEvenlySpaced from UserData rather than calling the mxGetPr
8-25
MATLAB API function. This results in a slight increase in performance.
8 Writing S-Functions for Real-Time Workshop
8-26
mdlRTW Usage
The Real-Time Workshop calls the mdlRTW routine while it (the Real-Time
Workshop) generates the model.rtw file. You can add information to the
model.rtw file about the mode in which your S-Function block is operating to
produce optimal code for your Simulink model.
This example adds the following information to the model.rtw file:
Parameters — These can be modified during execution by external mode. In
this example, the XData and YData S-function parameters can change during
execution and are written using the function ssWriteRTWParameters.
Parameter settings — These do not change during execution. In this case the
XDataEvenlySpaced S-function parameter cannot change during execution
(ssSetSFcnParamTunable was specified as false (0) for it in
mdlInitializeSizes). This example writes it out as a parameter setting
(XSpacing) using the function ssWriteRTWParamSettings.
Example Model
Before examining the S-function and the inlined TLC file, consider the
generated code for the following model.
When creating this model, you need to specify the following for each S-Function
block.
set_param(‘sfun_directlook_ex/S-Function’,’SFunctionModules’,’lookup_index’)
set_param(‘sfun_directlook_ex/S-Function1’,’SFunctionModules’,’lookup_index’)
This informs the Real-Time Workshop build process that the module
lookup_index.c is needed when creating the executable.
Fully Inlined S-Function with the mdlRTW Routine
The generated code for the lookup table example model is
<Generated header for sfun_directlook_ex model>
#include <math.h>
#include <string.h>
#include "sfun_directlook_ex.h"
#include "sfun_directlook_ex.prm"
/* Start the model */
void mdlStart(void)
{
/* (no start code required) */
}
/* Compute block outputs */
void mdlOutputs(int_T tid)
{
/* local block i/o variables */
real_T rtb_Sine_Wave;
real_T rtb_buffer2;
/* Sin Block: <Root>/Sine Wave */
rtb_Sine_Wave = rtP.Sine_Wave.Amplitude *
sin(rtP.Sine_Wave.Frequency * ssGetT(rtS) + rtP.Sine_Wave.Phase);
/* S-Function Block: <Root>/S-Function */
{
real_T *xData = &rtP.S_Function.XData[0];
real_T *yData = &rtP.S_Function.YData[0];
real_T spacing = xData[1] - xData[0];
if ( rtb_Sine_Wave <= xData[0] ) {
rtb_buffer2 = yData[0];
} else if ( rtb_Sine_Wave >= yData[20] ) {
rtb_buffer2 = yData[20];
} else {
int_T idx = (int_T)( ( rtb_Sine_Wave - xData[0] ) / spacing );
rtb_buffer2 = yData[idx];
}
}
/* Outport Block: <Root>/Out1 */
rtY.Out1 = rtb_buffer2;
This is the code that is
inlined for the top
S-Function block in the
sfun_directlook_ex.
model.
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8 Writing S-Functions for Real-Time Workshop
8-28
/* S-Function Block: <Root>/S-Function1 */
{
real_T *xData = &rtP.S_Function1.XData[0];
real_T *yData = &rtP.S_Function1.YData[0];
int_T idx;
idx = GetDirectLookupIndex(xData, 5, rtb_Sine_Wave);
rtb_buffer2 = yData[idx];
}
/* Outport Block: <Root>/Out2 */
rtY.Out2 = rtb_buffer2;
}
/* Perform model update */
void mdlUpdate(int_T tid)
{
/* (no update code required) */
}
/* Terminate function */
void mdlTerminate(void)
{
/* (no terminate code required) */
}
#include "sfun_directlook_ex.reg"
/* [EOF] sfun_directlook_ex.c */
matlabroot/simulink/src/sfun_directlook.c
/*
* File : sfun_directlook.c
* Abstract:
*
* Direct 1-D lookup. Here we are trying to compute an approximate
* solution p(x) to an unknown function f(x) at x=x0, given data point
* pairs (x,y) in the form of an x data vector and a y data vector. For a
* given data pair (say the ith pair), we have y_i = f(x_i). It is
* assumed that the x data values are monotonically increasing. If the
* x0 is outside of the range of the x data vector, then the first or
* last point will be returned.
*
* This function returns the "nearest" y0 point for a given x0. No
* interpolation is performed.
*
* The S-function parameters are:
* XData - double vector
* YData - double vector
* XDataEvenlySpacing - double scalar 0 (false) or 1 (true)
* The third parameter cannot be changed during simulation.
This is the code that is
inlined for the bottom
S-Function block in the
sfun_directlook_ex
model.
Fully Inlined S-Function with the mdlRTW Routine
*
* To build:
* mex sfun_directlook.c lookup_index.c
*
* Copyright (c) 1990-1998 by The MathWorks, Inc. All Rights Reserved.
*
*/
#define S_FUNCTION_NAME sfun_directlook
#define S_FUNCTION_LEVEL 2
#include <math.h>
#include "simstruc.h"
#include <float.h>
/*=========*
* Defines *
*=========*/
#define XVECT_PIDX 0
#define YVECT_PIDX 1
#define XDATAEVENLYSPACED_PIDX 2
#define NUM_PARAMS 3
#define XVECT(S) ssGetSFcnParam(S,XVECT_PIDX)
#define YVECT(S) ssGetSFcnParam(S,YVECT_PIDX)
#define XDATAEVENLYSPACED(S) ssGetSFcnParam(S,XDATAEVENLYSPACED_PIDX)
/*==============*
* misc defines *
*==============*/
#if !defined(TRUE)
#define TRUE 1
#endif
#if !defined(FALSE)
#define FALSE 0
#endif
/*===========*
* typedef’s *
*===========*/
typedef struct SFcnCache_tag {
boolean_T evenlySpaced;
} SFcnCache;
/*===================================================================*
* Prototype define for the function in separate file lookup_index.c *
*===================================================================*/
extern int_T GetDirectLookupIndex(const real_T *x, int_T xlen, real_T u);
8-29
8 Writing S-Functions for Real-Time Workshop
8-30
/*=========================*
* Local Utility Functions *
*=========================*/
/* Function: IsRealVect ========================================================
* Abstract:
* Verify that the mxArray is a real vector.
*/
static boolean_T IsRealVect(const mxArray *m)
{
if (mxIsNumeric(m) &&
mxIsDouble(m) &&
!mxIsLogical(m) &&
!mxIsComplex(m) &&
!mxIsSparse(m) &&
!mxIsEmpty(m) &&
mxGetNumberOfDimensions(m) == 2 &&
(mxGetM(m) == 1 || mxGetN(m) == 1))
{
real_T *data = mxGetPr(m);
int_T numEl = mxGetNumberOfElements(m);
int_T i;
for (i = 0; i < numEl; i++) {
if (!mxIsFinite(data[i])) {
return(FALSE);
}
}
return(TRUE);
} else {
return(FALSE);
}
}
/* end IsRealVect */
/*====================*
* S-function routines *
*====================*/
#define MDL_CHECK_PARAMETERS /* Change to #undef to remove function */
#if defined(MDL_CHECK_PARAMETERS) && defined(MATLAB_MEX_FILE)
/* Function: mdlCheckParameters ================================================
* Abstract:
* This routine will be called after mdlInitializeSizes, whenever
* parameters change or get reevaluated. The purpose of this routine is
* to verify that the new parameter settings are correct.
*
Fully Inlined S-Function with the mdlRTW Routine
* You should add a call to this routine from mdlInitializeSizes
* to check the parameters. After setting your sizes elements, you should:
* if (ssGetSFcnParamsCount(S) == ssGetNumSFcnParams(S)) {
* mdlCheckParameters(S);
* }
*/
static void mdlCheckParameters(SimStruct *S)
{
if (!IsRealVect(XVECT(S))) {
ssSetErrorStatus(S,"1st, X-vector parameter must be a real finite vector");
return;
}
if (!IsRealVect(YVECT(S))) {
ssSetErrorStatus(S,"2nd, Y-vector parameter must be a real finite "
"vector");
return;
}
/*
* Verify that the dimensions of X and Y are the same.
*/
if (mxGetNumberOfElements(XVECT(S)) != mxGetNumberOfElements(YVECT(S)) ||
mxGetNumberOfElements(XVECT(S)) == 1) {
ssSetErrorStatus(S,"X and Y-vectors must be of the same dimension "
"and have at least two elements");
return;
}
/*
* Verify we have a valid XDataEvenlySpaced parameter.
*/
if (!mxIsNumeric(XDATAEVENLYSPACED(S)) ||
!(mxIsDouble(XDATAEVENLYSPACED(S)) ||
mxIsLogical(XDATAEVENLYSPACED(S))) ||
mxIsComplex(XDATAEVENLYSPACED(S)) ||
mxGetNumberOfElements(XDATAEVENLYSPACED(S)) != 1) {
ssSetErrorStatus(S,"3rd, X-evenly-spaced parameter must be scalar "
"(0.0=false, 1.0=true)");
return;
}
/*
* Verify x-data is correctly spaced.
*/
{
int_T i;
boolean_T spacingEqual;
real_T *xData = mxGetPr(XVECT(S));
int_T numEl = mxGetNumberOfElements(XVECT(S));
8-31
/*
8 Writing S-Functions for Real-Time Workshop
8-32
* spacingEqual is TRUE if user XDataEvenlySpaced
*/
spacingEqual = (mxGetScalar(XDATAEVENLYSPACED(S)) != 0.0);
if (spacingEqual) { /* XData is 'evenly-spaced' */
boolean_T badSpacing = FALSE;
real_T spacing = xData[1] - xData[0];
real_T space;
if (spacing <= 0.0) {
badSpacing = TRUE;
} else {
real_T eps = DBL_EPSILON;
for (i = 2; i < numEl; i++) {
space = xData[i] - xData[i-1];
if (space <= 0.0 ||
fabs(space-spacing) >= 128.0*eps*spacing ){
badSpacing = TRUE;
break;
}
}
}
if (badSpacing) {
ssSetErrorStatus(S,"X-vector must be an evenly spaced "
"strictly monotonically increasing vector");
return;
}
} else { /* XData is 'unevenly-spaced' */
for (i = 1; i < numEl; i++) {
if (xData[i] <= xData[i-1]) {
ssSetErrorStatus(S,"X-vector must be a strictly "
"monotonically increasing vector");
return;
}
}
}
}
}
#endif /* MDL_CHECK_PARAMETERS */
/* Function: mdlInitializeSizes ================================================
* Abstract:
* The sizes information is used by Simulink to determine the S-function
* block’s characteristics (number of inputs, outputs, states, etc.).
*/
static void mdlInitializeSizes(SimStruct *S)
{
ssSetNumSFcnParams(S, NUM_PARAMS); /* Number of expected parameters */
Fully Inlined S-Function with the mdlRTW Routine
/*
* Check parameters passed in, providing the correct number was specified
* in the S-function dialog box. If an incorrect number of parameters
* was specified, Simulink will detect the error since ssGetNumSFcnParams
* and ssGetSFcnParamsCount will differ.
* ssGetNumSFcnParams - This sets the number of parameters your
* S-function expects.
* ssGetSFcnParamsCount - This is the number of parameters entered by
* the user in the Simulink S-function dialog box.
*/
#if defined(MATLAB_MEX_FILE)
if (ssGetNumSFcnParams(S) == ssGetSFcnParamsCount(S)) {
mdlCheckParameters(S);
if (ssGetErrorStatus(S) != NULL) {
return;
}
} else {
return; /* Parameter mismatch will be reported by Simulink */
}
#endif
ssSetNumContStates(S, 0);
ssSetNumDiscStates(S, 0);
if (!ssSetNumInputPorts(S, 1)) return;
ssSetInputPortWidth(S, 0, DYNAMICALLY_SIZED);
ssSetInputPortDirectFeedThrough(S, 0, 1);
ssSetInputPortTestPoint(S, 0, FALSE);
ssSetInputPortOverWritable(S, 0, TRUE);
if (!ssSetNumOutputPorts(S, 1)) return;
ssSetOutputPortWidth(S, 0, DYNAMICALLY_SIZED);
ssSetOutputPortTestPoint(S, 0, FALSE);
ssSetNumSampleTimes(S, 1);
ssSetSFcnParamTunable(S, XDATAEVENLYSPACED_PIDX, 0);
ssSetOptions(S, SS_OPTION_EXCEPTION_FREE_CODE);
} /* mdlInitializeSizes */
/* Function: mdlInitializeSampleTimes ==========================================
* Abstract:
* The lookup inherits its sample time from the driving block.
*/
static void mdlInitializeSampleTimes(SimStruct *S)
{
ssSetSampleTime(S, 0, INHERITED_SAMPLE_TIME);
8-33
ssSetOffsetTime(S, 0, 0.0);
8 Writing S-Functions for Real-Time Workshop
8-34
} /* end mdlInitializeSampleTimes */
#define MDL_START /* Change to #undef to remove function */
#if defined(MDL_START)
/* Function: mdlStart ==========================================================
* Abstract:
* Here we cache the state (true/false) of the XDATAEVENLYSPACED parameter.
* We do this primarily to illustrate how to "cache" parameter values (or
* information that is computed from parameter values) that do not change
* for the duration of the simulation (or in the generated code). In this
* case, rather than repeated calls to mxGetPr, we save the state once.
* This results in a slight increase in performance.
*/
static void mdlStart(SimStruct *S)
{
SFcnCache *cache = malloc(sizeof(SFcnCache));
if (cache == NULL) {
ssSetErrorStatus(S,"memory allocation error");
return;
}
ssSetUserData(S, cache);
if (mxGetScalar(XDATAEVENLYSPACED(S)) != 0.0){
cache->evenlySpaced = TRUE;
}else{
cache->evenlySpaced = FALSE;
}
}
#endif /* MDL_START */
/* Function: mdlOutputs ========================================================
* Abstract:
* In this function, we compute the outputs of our S-function
* block. Generally outputs are placed in the output vector, ssGetY(S).
*/
static void mdlOutputs(SimStruct *S, int_T tid)
{
SFcnCache *cache = ssGetUserData(S);
real_T *xData = mxGetPr(XVECT(S));
real_T *yData = mxGetPr(YVECT(S));
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
real_T *y = ssGetOutputPortRealSignal(S,0);
int_T ny = ssGetOutputPortWidth(S,0);
int_T xLen = mxGetNumberOfElements(XVECT(S));
int_T i;
Fully Inlined S-Function with the mdlRTW Routine
/*
* When the XData is evenly spaced, we use the direct lookup algorithm
* to calculate the lookup
*/
if (cache->evenlySpaced) {
real_T spacing = xData[1] - xData[0];
for (i = 0; i < ny; i++) {
real_T u = *uPtrs[i];
if (u <= xData[0]) {
y[i] = yData[0];
} else if (u >= xData[xLen-1]) {
y[i] = yData[xLen-1];
} else {
int_T idx = (int_T)((u - xData[0])/spacing);
y[i] = yData[idx];
}
}
} else {
/*
* When the XData is unevenly spaced, we use a bisection search to
* locate the lookup index.
*/
for (i = 0; i < ny; i++) {
int_T idx = GetDirectLookupIndex(xData,xLen,*uPtrs[i]);
y[i] = yData[idx];
}
}
} /* end mdlOutputs */
/* Function: mdlTerminate ======================================================
* Abstract:
* Free the cache that was allocated in mdlStart.
*/
static void mdlTerminate(SimStruct *S)
{
SFcnCache *cache = ssGetUserData(S);
if (cache != NULL) {
free(cache);
}
} /* end mdlTerminate */
#define MDL_RTW /* Change to #undef to remove function */
#if defined(MDL_RTW) && (defined(MATLAB_MEX_FILE) || defined(NRT))
/* Function: mdlRTW ============================================================
* Abstract:
* This function is called when the Real-Time Workshop is generating the
8-35
* model.rtw file. In this routine, you can call the following functions
8 Writing S-Functions for Real-Time Workshop
8-36
* which add fields to the model.rtw file.
*
* Important! Since this S-function has this mdlRTW routine, it must have
* a corresponding .tlc file to work with the Real-Time Workshop. You will find
* the sfun_directlook.tlc in the same directory as sfun_directlook.dll.
*/
static void mdlRTW(SimStruct *S)
{
/*
* Write out the [X,Y] data as parameters, i.e., these values can be
* changed during execution.
*/
{
real_T *xData = mxGetPr(XVECT(S));
int_T xLen = mxGetNumberOfElements(XVECT(S));
real_T *yData = mxGetPr(YVECT(S));
int_T yLen = mxGetNumberOfElements(YVECT(S));
if (!ssWriteRTWParameters(S,2,
SSWRITE_VALUE_VECT,"XData","",xData,xLen,
SSWRITE_VALUE_VECT,"YData","",yData,yLen)) {
return; /* An error occurred which will be reported by Simulink */
}
}
/*
* Write out the spacing setting as a param setting, i.e., this cannot be
* changed during execution.
*/
{
boolean_T even = (mxGetScalar(XDATAEVENLYSPACED(S)) != 0.0);
if (!ssWriteRTWParamSettings(S, 1,
SSWRITE_VALUE_QSTR,
"XSpacing",
even ? "EvenlySpaced" : "UnEvenlySpaced")){
return;/* An error occurred which will be reported by Simulink */
}
}
}
#endif /* MDL_RTW */
/*=============================*
* Required S-function trailer *
*=============================*/
#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration function */
#endif
Fully Inlined S-Function with the mdlRTW Routine
/* [EOF] sfun_directlook.c */
matlabroot/simulink/src/lookup_index.c
/* File : lookup_index.c
* Abstract:
*
* Contains a routine used by the S-function sfun_directlookup.c to
* compute the index in a vector for a given data value.
*
* Copyright (c) 1990-1998 by The MathWorks, Inc. All Rights Reserved.
*
*/
#include "tmwtypes.h"
/*
* Function: GetDirectLookupIndex ==============================================
* Abstract:
* Using a bisection search to locate the lookup index when the x-vector
* isn’t evenly spaced.
*
* Inputs:
* *x : Pointer to table, x[0] ....x[xlen-1]
* xlen : Number of values in xtable
* u : input value to look up
*
* Output:
* idx : the index into the table such that:
* if u is negative
* x[idx] <= u < x[idx+1]
* else
* x[idx] < u <= x[idx+1]
*/
int_T GetDirectLookupIndex(const real_T *x, int_T xlen, real_T u)
{
int_T idx = 0;
int_T bottom = 0;
int_T top = xlen-1;
/*
* Deal with the extreme cases first:
*
* i] u <= x[bottom] then idx = bottom
* ii] u >= x[top] then idx = top-1
*
*/
if (u <= x[bottom]) {
return(bottom);
} else if (u >= x[top]) {
return(top);
}
8-37
8 Writing S-Functions for Real-Time Workshop
8-38
/*
* We have: x[bottom] < u < x[top], onward
* with search for the appropriate index ...
*/
for (;;) {
idx = (bottom + top)/2;
if (u < x[idx]) {
top = idx;
} else if (u > x[idx+1]) {
bottom = idx + 1;
} else {
/*
* We have: x[idx] <= u <= x[idx+1], only need
* to do two more checks and we have the answer.
*/
if (u < 0) {
/*
* We want right continuity, i.e.,
* if u == x[idx+1]
* then x[idx+1] <= u < x[idx+2]
* else x[idx ] <= u < x[idx+1]
*/
return( (u == x[idx+1]) ? (idx+1) : idx);
} else {
/*
* We want left continuity, i.e.,
* if u == x[idx]
* then x[idx-1] < u <= x[idx ]
* else x[idx ] < u <= x[idx+1]
*/
return( (u == x[idx]) ? (idx-1) : idx);
}
}
}
} /* end GetDirectLookupIndex */
/* [EOF] lookup_index.c */
Fully Inlined S-Function with the mdlRTW Routine
matlabroot/toolbox/simulink/blocks/tlc_c/sfun_directlook.tlc
%% File : sfun_directlook.tlc
%% Abstract:
%% Level-2 S-function sfun_directlook block target file.
%% It is using direct lookup algorithm without interpolation.
%%
%% Copyright (c) 1994-1998 by The MathWorks, Inc. All Rights Reserved.
%%
%implements "sfun_directlook" "C"
%% Function: BlockTypeSetup ====================================================
%% Abstract:
%% Place include and function prototype in the model’s header file.
%%
%function BlockTypeSetup(block, system) void
%% Add this external function’s prototype in the header of the generated
%% file.
%%
%openfile buffer
extern int_T GetDirectLookupIndex(const real_T *x, int_T xlen, real_T u);
%closefile buffer
%<LibCacheFunctionPrototype(buffer)>
%endfunction
%% Function: mdlOutputs ========================================================
%% Abstract:
%% Direct 1-D lookup table S-function example.
%% Here we are trying to compute an approximate solution p(x) to an
%% unknown function f(x) at x=x0, given data point pairs (x,y) in the
%% form of an x-data vector and a y-data vector. For a given data pair
%% (say the ith pair), we have y_i = f(x_i). It is assumed that the x
%% data values are monotonically increasing. If the first or last x is
%% outside of the range of the x data vector, then the first or last
%% point will be returned.
%%
%% This function returns the "nearest" y0 point for a given x0.
%% No interpolation is performed.
%%
%% The S-function parameters are:
%% XData
%% YData
%% XEvenlySpaced: 0 or 1
%% The third parameter cannot be changed during execution and is
%% written to the model.rtw file in XSpacing field of the SFcnParamSettings
%% record as "EvenlySpaced" or "UnEvenlySpaced". The first two parameters
%% can change during execution and show up in the parameter vector.
8-39
%%
8 Writing S-Functions for Real-Time Workshop
8-40
%function Outputs(block, system) Output
/* %<Type> Block: %<Name> */
{
%assign rollVars = ["U", "Y"]
%%
%% Load XData and YData as local variables
%%
real_T *xData = %<LibBlockParameterAddr(XData, "", "", 0)>;
real_T *yData = %<LibBlockParameterAddr(YData, "", "", 0)>;
%assign xDataLen = SIZE(XData.Value, 1)
%%
%% When the XData is evenly spaced, we use the direct lookup algorithm
%% to locate the lookup index.
%%
%if SFcnParamSettings.XSpacing == "EvenlySpaced"
real_T spacing = xData[1] - xData[0];
%roll idx = RollRegions, lcv = RollThreshold, block, "Roller", rollVars
%assign u = LibBlockInputSignal(0, "", lcv, idx)
%assign y = LibBlockOutputSignal(0, "", lcv, idx)
if ( %<u> <= xData[0] ) {
%<y> = yData[0];
} else if ( %<u> >= yData[%<xDataLen-1>] ) {
%<y> = yData[%<xDataLen-1>];
} else {
int_T idx = (int_T)( ( %<u> - xData[0] ) / spacing );
%<y> = yData[idx];
}
%%
%% Generate an empty line if we are not rolling,
%% so that it looks nice in the generated code.
%%
%if lcv == ""
%endif
%endroll
%else
%% When the XData is unevenly spaced, we use a bisection search to
%% locate the lookup index.
int_T idx;
%assign xDataAddr = LibBlockParameterAddr(XData, "", "", 0)
%roll idx = RollRegions, lcv = RollThreshold, block, "Roller", rollVars
%assign u = LibBlockInputSignal(0, "", lcv, idx)
idx = GetDirectLookupIndex(xData, %<xDataLen>, %<u>);
%assign y = LibBlockOutputSignal(0, "", lcv, idx)
%<y> = yData[idx];
%%
%% Generate an empty line if we are not rolling,
%% so that it looks nice in the generated code.
%%
%if lcv == ""
Fully Inlined S-Function with the mdlRTW Routine
%endif
%endroll
%endif
}
%endfunction
%% EOF: sfun_directlook.tlc
8-41
8 Writing S-Functions for Real-Time Workshop
8-42
Creating Code-Reuse-Compatible S-Functions
The code reuse feature of the Real-Time Workshop generates code for a
subsystem in the form of a function that is invoked wherever the subsystem
occurs in the model (see “Nonvirtual Subsystem Code Generation Options” in
the online Real-Time Workshop documentation). If a subsystem contains
S-functions, the S-functions must be compatible with the code reuse feature.
Otherwise, the Real-Time Workshop may not generate reusable code from the
subsystem or may generate incorrect code.
If you want your S-function to support the subsystem code reuse feature, you
must ensure that the S-function meets the following requirements:
The S-function must be inlined.
Code generated from the S-function must not use static variables.
The TLC code that generates the inlined S-function code must not use the
BlockInstanceData function.
The S-function must initialize its pointer work vector in mdlStart and not
before.
The S-function must not be a sink that logs data to the workspace.
The S-function must register its parameters as run time parameters in
mdlSetWorkWidths. (It must not use ssWriteRTWParameters in its mdlRTW
function for this purpose.)
In addition to meeting the preceding requirements, your S-function must set
the SS_OPTION_WORKS_WITH_CODE_REUSE flag (see ssSetOptions). This flag
assures RTW that your S-function meets the requirements for subsystem code
reuse.
9
S-Function Callback
Methods
Every user-written S-function must implement a set of methods, called callback methods or simply
callbacks, that Simulink invokes when simulating a model that contains the S-function. Some
callback methods are optional. Simulink invokes an optional callback only if the S-function defines
the callback. This section describes the purpose and syntax of all callback methods that an S-function
can implement. In each case, the documentation for a callback method indicates whether it is
required or optional.
mdlCheckParameters
9mdlCheckParameters
Purpose Check the validity of an S-function’s parameters.
Syntax void mdlCheckParameters(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Verifies new parameter settings whenever parameters change or are
reevaluated during a simulation.
When a simulation is running, changes to S-function parameters can occur at
any time during the simulation loop, that is, either at the start of a simulation
step or during a simulation step. When the change occurs during a simulation
step, Simulink calls this routine twice to handle the parameter change. The
first call during the simulation step is used to verify that the parameters are
correct. After verifying the new parameters, the simulation continues using the
original parameter values until the next simulation step, at which time the
new parameter values are used. Redundant calls are needed to maintain
simulation consistency.
Note You cannot access the work, state, input, output, and other vectors in
this routine. Use this routine only to validate the parameters. Additional
processing of the parameters should be done in mdlProcessParameters.
Example This example checks the first S-function parameter to verify that it is a real
nonnegative scalar.
#define PARAM1(S) ssGetSFcnParam(S,0)
#define MDL_CHECK_PARAMETERS /* Change to #undef to remove function */
#if defined(MDL_CHECK_PARAMETERS) && defined(MATLAB_MEX_FILE)
static void mdlCheckParameters(SimStruct *S)
{
if (mxGetNumberOfElements(PARAM1(S)) != 1) {
ssSetErrorStatus(S,"Parameter to S-function must be a scalar");
return;
} else if (mxGetPr(PARAM1(S))[0] < 0) {
ssSetErrorStatus(S, "Parameter to S-function must be nonnegative");
return;
}
}
#endif /* MDL_CHECK_PARAMETERS */
9-2
mdlCheckParameters
In addition to the preceding routine, you must add a call to this routine from
mdlInitializeSizes to check parameters during initialization, because
mdlCheckParameters is only called while the simulation is running. To do this,
after setting the number of parameters you expect in your S-function by using
ssSetNumSFcnParams, use this code in mdlInitializeSizes:
static void mdlInitializeSizes(SimStruct *S)
{
ssSetNumSFcnParams(S, 1); /* Number of expected parameters */
#if defined(MATLAB_MEX_FILE)
if(ssGetNumSFcnParams(s) == ssGetSFcnParamsCount(s) {
mdlCheckParameters(S);
if(ssGetErrorStates(S) != NULL) return;
} else {
return; /* Simulink will report a mismatch error. */
}
#endif
...
}
Note The macro ssGetSFcnParamsCount returns the actual number of
parameters entered in the dialog box.
See matlabroot/simulink/src/sfun_errhdl.c for an example.
Languages Ada, C
See Also mdlProcessParameters, ssGetSFcnParamsCount
9-3
mdlDerivatives
9mdlDerivatives
Purpose Compute the S-function’s derivatives.
Syntax void mdlDerivatives(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Simulink invokes this optional method at each time step to compute the
derivatives of the S-function’s continuous states. This method should store the
derivatives in the S-function’s state derivatives vector. This method can use
ssGetdX to get a pointer to the derivatives vector.
Each time the mdlDerivatives routine is called, it must explicitly set the
values of all derivatives. The derivative vector does not maintain the values
from the last call to this routine. The memory allocated to the derivative vector
changes during execution.
Example For an example, see matlabroot/simulink/src/csfunc.c.
Languages Ada, C, M
See Also ssGetdx
9-4
mdlGetTimeOfNextVarHit
9mdlGetTimeOfNextVarHit
Purpose Initialize the state vectors of this S-function.
Syntax void mdlGetTimeOfNextVarHit(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Simulink invokes this optional method at every major integration step to get
the time of the next sample time hit. This method should set the time of next
hit, using ssSetTNext. The time of the next hit must be greater than the
current simulation time as returned by ssGetT. The S-function must
implement this method if it operates at a discrete, variable-step sample time.
Note The time of the next hit can be a function of the input signals.
Languages C, M
Example static void mdlGetTimeOfNextVarHit(SimStruct *S)
{
time_T offset = getOffset();
time_T timeOfNextHit = ssGetT(S) + offset;
ssSetTNext(S, timeOfNextHit);
}
See Also mdlInitializeSampleTimes, ssSetTNext, ssGetT
9-5
mdlInitializeConditions
9mdlInitializeConditions
Purpose Initialize the state vectors of this S-function.
Syntax void mdlInitializeConditions(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Simulink invokes this optional method at the beginning of a simulation. It
should initialize the continuous and discrete states, if any, of this S-Function
block. Use ssGetContStates and/or ssGetDiscStates to get the states. This
method can also perform any other initialization activities that this S-function
requires.
If this S-function resides in an enabled subsystem configured to reset states,
Simulink also calls this method when the enabled subsystem restarts
execution. This method can use ssIsFirstInitCond macro to determine
whether it is being called for the first time.
Example This example is an S-function with both continuous and discrete states. It
initializes both sets of states to 1.0:
#define MDL_INITIALIZE_CONDITIONS /* Change to #undef to remove function */
#if defined(MDL_INITIALIZE_CONDITIONS)
static void mdlInitializeConditions(SimStruct *S)
{
int i;
real_T *xcont = ssGetContStates(S);
int_T nCStates = ssGetNumContStates(S);
real_T *xdisc = ssGetRealDiscStates(S);
int_T nDStates = ssGetNumDiscStates(S);
for (i = 0; i < nCStates; i++) {
*xcont++ = 1.0;
}
for (i = 0; i < nDStates; i++) {
*xdisc++ = 1.0;
}
}
#endif /* MDL_INITIALIZE_CONDITIONS */
For another example that initializes only the continuous states, see
matlabroot/simulink/src/resetint.c.
9-6
mdlInitializeConditions
Languages C
See Also mdlStart, ssIsFirstInitCond, ssGetContStates, ssGetDiscStates
9-7
mdlInitializeSampleTimes
9mdlInitializeSampleTimes
Purpose Specify the sample rates at which this S-function operates.
Syntax void mdlInitializeSampleTimes(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description This method should specify the sample time and offset time for each sample
rate at which this S-function operates via the following paired macros
ssSetSampleTime(S, sampleTimeIndex, sample_time)
ssSetOffsetTime(S, offsetTimeIndex, offset_time)
where sampleTimeIndex runs from 0 to one less than the number of sample
times specified in mdlInitializeSizes via ssSetNumSampleTimes.
If the S-function operates at one or more sample rates, this method can specify
any of the following sample time and offset values for a given sample time:
[CONTINUOUS_SAMPLE_TIME, 0.0]
[CONTINUOUS_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]
[discrete_sample_period, offset]
[VARIABLE_SAMPLE_TIME, 0.0]
The uppercase values are macros defined in simstruc.h.
If the S-function operates at one rate, this method can alternatively set the
sample time to one of the following sample/offset time pairs.
[INHERITED_SAMPLE_TIME, 0.0]
[INHERITED_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]
If the number of sample times is 0, Simulink assumes that the S-function
inherits its sample time from the block to which it is connected, i.e., that the
sample time is
[INHERITED_SAMPLE_TIME, 0.0]
This method can therefore return without doing anything.
Use the following guidelines when specifying sample times.
A continuous function that changes during minor integration steps should
set the sample time to
9-8
mdlInitializeSampleTimes
[CONTINUOUS_SAMPLE_TIME, 0.0]
A continuous function that does not change during minor integration steps
should set the sample time to
[CONTINUOUS_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]
A discrete function that changes at a specified rate should set the sample
time to
[discrete_sample_period, offset]
where
discrete_sample_period > 0.0
and
0.0 <= offset < discrete_sample_period
A discrete function that changes at a variable rate should set the sample
time to
[VARIABLE_SAMPLE_TIME, 0.0]
Simulink invokes the mdlGetTimeOfNextVarHit function to get the time of
the next sample hit for the variable-step discrete task.
Note that VARIABLE_SAMPLE_TIME requires a variable-step solver.
To operate correctly in a triggered subsystem or a periodic system, a discrete
S-function should
- Specify a single sample time set to
[INHERITED_SAMPLE_TIME, 0.0]
- Use ssSetOptions to set the
SS_OPTION_DISALLOW_CONSTANT_SAMPLE_TIME simulation option in
mdlInitializeSizes
- Verify that it was assigned a discrete or triggered sample time in
mdlSetWorkWidths:
if (ssGetSampleTime(S, 0) == CONTINUOUS_SAMPLE_TIME) {
ssSetErrorStatus(S,
"This block cannot be assigned a continuous sample time");
9-9
mdlInitializeSampleTimes
}
After propagating sample times throughout the block diagram, Simulink
assigns the sample time
[INHERITED_SAMPLE_TIME, INHERITED_SAMPLE_TIME]
to discrete blocks residing in triggered subsystems.
If this function has no intrinsic sample time, it should set its sample time to
inherited according to the following guidelines:
A function that changes as its input changes, even during minor integration
steps, should set its sample time to
[INHERITED_SAMPLE_TIME, 0.0]
A function that changes as its input changes, but doesn’t change during
minor integration steps (i.e., is held during minor steps) should set its
sample time to
[INHERITED_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]
The S-function should use the ssIsSampleHit or ssIsContinuousTask macros
to check for a sample hit during execution (in mdlOutputs or mdlUpdate). For
example, if the block’s first sample time is continuous, the function can use the
following code fragment to check for a sample hit.
if (ssIsContinuousTask(S,tid)) {
}
Note The function receives incorrect results if it uses
ssIsSampleHit(S,0,tid).
If the function wants to determine whether the third (discrete) task has a hit,
it can use the following code fragment.
if (ssIsSampleHit(S,2,tid) {
}
Languages C
9-10
mdlInitializeSampleTimes
See Also mdlSetInputPortSampleTime, mdlSetOutputPortSampleTime
9-11
mdlInitializeSizes
9mdlInitializeSizes
Purpose Specify the number of inputs, outputs, states, parameters, and other
characteristics of the S-function.
Syntax void mdlInitializeSizes(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description This is the first of the S-function’s callback methods that Simulink calls. This
method should perform the following tasks:
Specify the number of parameters that this S-function supports, using
ssSetNumSFcnParams.
Use ssSetSFcnParamTunable(S,paramIdx, 0) when a parameter cannot
change during simulation, where paramIdx starts at 0. When a parameter
has been specified as not tunable, Simulink issues an error during
simulation (or the Real-Time Workshop external mode) if an attempt is made
to change the parameter.
Specify the number of states that this function has, using
ssSetNumContStates and ssSetNumDiscStates.
Configure the block’s input ports.
This entails the following tasks:
- Specify the number of input ports that this S-function has, using
ssSetNumInputPorts.
- Specify the dimensions of the input ports.
See“Dynamically Sized Block Features” on page 9-13 for more
information.
- For each input port, specify whether it has direct feedthrough, using
ssSetInputPortDirectFeedThrough.
A port has direct feedthrough if the input is used in either the mdlOutputs
or mdlGetTimeOfNextVarHit function. The direct feedthrough flag for each
input port can be set to either 1=yes or 0=no. It should be set to 1 if the
input, u, is used in the mdlOutputs or mdlGetTimeOfNextVarHit routine.
Setting the direct feedthrough flag to 0 tells Simulink that u is not used in
either of these S-function routines. Violating this leads to unpredictable
results.
9-12
mdlInitializeSizes
Configure the block’s output ports.
This entails the following tasks:
- Specify the number of output ports that the block has, using
ssSetNumOutputPorts.
- Specify the dimensions of the output ports.
See mdlSetOutputPortDimensionInfo for more information.
If your S-function outputs are discrete (e.g., can only take the values 1 and
2), specify SS_OPTION_DISCRETE_VALUED_OUTPUT.
Set the number of sample times (i.e., sample rates) at which the block
operates.
There are two ways of specifying sample times:
- Port-based sample times
- Block-based sample times
See “Sample Times” on page 7-15 for a complete discussion of sample time
issues.
For multirate S-functions, the suggested approach to setting sample times is
via the port-based sample times method. When you create a multirate
S-function, you must take care to verify that, when slower tasks are
preempted, your S-function correctly manages data so as to avoid race
conditions. When port-based sample times are specified, the block cannot
inherit a constant sample time at any port.
Set the size of the block’s work vectors, using ssSetNumRWork,
ssSetNumIWork, ssSetNumPWork, ssSetNumModes, ssSetNumNonsampledZCs.
Set the simulation options that this block implements, using ssSetOptions.
All options have the form SS_OPTION_<name>. See ssSetOptions for
information on each option. The options should be bitwise OR’d together, as
in
ssSetOptions(S, (SS_OPTION_name1 | SS_OPTION_name2))
Dynamically Sized Block Features
You can set the parameters NumContStates, NumDiscStates, NumInputs,
NumOutputs, NumRWork, NumIWork, NumPWork, NumModes, and NumNonsampledZCs
to a fixed nonnegative integer or tell Simulink to size them dynamically:
9-13
mdlInitializeSizes
DYNAMICALLY_SIZED — Sets lengths of states, work vectors, and so on to
values inherited from the driving block. It sets widths to the actual input
widths, according to the scalar expansion rules unless you use
mdlSetWorkWidths to set the widths.
0 or positive number — Sets lengths (or widths) to the specified values. The
default is 0.
Languages Ada, C, M
Example static void mdlInitializeSizes(SimStruct *S)
{
int_T nInputPorts = 1; /* number of input ports */
int_T nOutputPorts = 1; /* number of output ports */
int_T needsInput = 1; /* direct feed through */
int_T inputPortIdx = 0;
int_T outputPortIdx = 0;
ssSetNumSFcnParams(S, 0); /* Number of expected parameters */
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
/*
* If the the number of expected input parameters is not
* equal to the number of parameters entered in the
* dialog box, return. Simulink will generate an error
* indicating that there is aparameter mismatch.
*/
return;
}else {
mdlCheckParameters(S);
if (ssGetErrorStatus(s) != NULL)
return;
}
ssSetNumContStates( S, 0);
ssSetNumDiscStates( S, 0);
/*
* Configure the input ports. First set the number of input
* ports.
*/
if (!ssSetNumInputPorts(S, nInputPorts)) return;
/*
* Set input port dimensions for each input port index
* starting at 0.
9-14
*/
mdlInitializeSizes
if(!ssSetInputPortDimensionInfo(S, inputPortIdx,
DYNAMIC_DIMENSION)) return;
/*
* Set direct feedthrough flag (1=yes, 0=no).
*/
ssSetInputPortDirectFeedThrough(S, inputPortIdx, needsInput);
/*
* Configure the output ports. First set the number of
* output ports.
*/
if (!ssSetNumOutputPorts(S, nOutputPorts)) return;
/*
* Set output port dimensions for each output port index
* starting at 0.
*/
if(!ssSetOutputPortDimensionInfo(S,outputPortIdx,
DYNAMIC_DIMENSION)) return;
/*
* Set the number of sample times. */
ssSetNumSampleTimes(S, 1);
/*
* Set size of the work vectors.
*/
ssSetNumRWork(S, 0); /* real vector */
ssSetNumIWork(S, 0); /* integer vector */
ssSetNumPWork(S, 0); /* pointer vector */
ssSetNumModes(S, 0); /* mode vector */
ssSetNumNonsampledZCs(S, 0); /* zero crossings */
ssSetOptions(S, 0);
} /* end mdlInitializeSizes */
9-15
mdlOutputs
9mdlOutputs
Purpose Compute the signals that this block emits.
Syntax void mdlOutputs(SimStruct *S, int_T tid)
Arguments S
SimStruct representing an S-Function block.
tid
Task ID.
Description Simulink invokes this required method at each simulation time step. The
method should compute the S-function’s outputs at the current time step and
store the results in the S-function’s output signal arrays.
The tid (task ID) argument specifies the task running when the mdlOutputs
routine is invoked. You can use this argument in the mdlOutports routine of a
multirate S-Function block to encapsulate task-specific blocks of code (see
“Multirate S-Function Blocks” on page 7-23).
For an example of an mdlOutputs routine that works with multiple input and
output ports, see matlabroot/simulink/src/sfun_multiport.c.
Languages A, C, M
See Also ssGetOutputPortSignal, ssGetOutputPortRealSignal,
ssGetOutputPortComplexSignal
9-16
mdlProcessParameters
9mdlProcessParameters
Purpose Process the S-function’s parameters.
Syntax void mdlProcessParameters(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description This is an optional routine that Simulink calls after mdlCheckParameters
changes and verifies parameters. The processing is done at the top of the
simulation loop when it is safe to process the changed parameters. This routine
can only be used in a C MEX S-function.
The purpose of this routine is to process newly changed parameters. An
example is to cache parameter changes in work vectors. Simulink does not call
this routine when it is used with the Real-Time Workshop. Therefore, if you use
this routine in an S-function designed for use with the Real-Time Workshop,
you must write your S-function so that it doesn’t rely on this routine. To do this,
you must inline your S-function by using the Target Language Compiler. See
The Target Language Compiler Reference Guide for information on inlining
S-functions.
The synopsis is
#define MDL_PROCESS_PARAMETERS /* Change to #undef to remove function */
#if defined(MDL_PROCESS_PARAMETERS) && defined(MATLAB_MEX_FILE)
static void mdlProcessParameters(SimStruct *S)
{
}
#endif /* MDL_PROCESS_PARAMETERS */
Example This example processes a string parameter that mdlCheckParameters has
verified to be of the form '+++' (where there could be any number of '+' or '-'
characters).
#define MDL_PROCESS_PARAMETERS /* Change to #undef to remove function */
9-17
mdlProcessParameters
#if defined(MDL_PROCESS_PARAMETERS) && defined(MATLAB_MEX_FILE)
static void mdlProcessParameters(SimStruct *S)
{
int_T i;
char_T *plusMinusStr;
int_T nInputPorts = ssGetNumInputPorts(S);
int_T *iwork = ssGetIWork(S);
if ((plusMinusStr=(char_T*)malloc(nInputPorts+1)) == NULL) {
ssSetErrorStatus(S,"Memory allocation error in mdlStart");
return;
}
if (mxGetString(SIGNS_PARAM(S),plusMinusStr,nInputPorts+1) != 0) {
free(plusMinusStr);
ssSetErrorStatus(S,"mxGetString error in mdlStart");
return;
}
for (i = 0; i < nInputPorts; i++) {
iwork[i] = plusMinusStr[i] == '+'? 1: -1;
}
free(plusMinusStr);
}
#endif /* MDL_PROCESS_PARAMETERS */
mdlProcessParameters is called from mdlStart to load the signs string prior to
the start of the simulation loop.
#define MDL_START
#if defined(MDL_START)
static void mdlStart(SimStruct *S)
{
mdlProcessParameters(S);
}
#endif /* MDL_START */
For more details on this example, see matlabroot/simulink/src/
sfun_multiport.c.
Languages Ada, C, M
See Also mdlCheckParameters
9-18
mdlRTW
9mdlRTW
Purpose Generate code generation data.
Syntax void mdlRTW(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description This function is called when the Real-Time Workshop is generating the
model.rtw file. In this method, you can call the following functions that add
fields to the model.rtw file:
ssWriteRTWParameters
ssWriteRTWParamSettings
ssWriteRTWWorkVect
ssWriteRTWStr
ssWriteRTWStrParam
ssWriteRTWScalarParam
ssWriteRTWStrVectParam
ssWriteRTWVectParam
ssWriteRTW2dMatParam
ssWriteRTWMxVectParam
ssWriteRTWMx2dMatParam
Languages C
See Also ssSetInputPortFrameData, ssSetOutputPortFrameData, ssSetErrorStatus
9-19
mdlSetDefaultPortComplexSignals
9mdlSetDefaultPortComplexSignals
Purpose Set the numeric types (real, complex, or inherited) of ports whose numeric
types cannot be determined from block connectivity.
Syntax void mdlSetDefaultPortComplexSignals(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Simulink invokes this method if the block has ports whose numeric types
cannot be determined from connectivity. (This usually happens when the block
is unconnected or is part of a feedback loop.) This method must set the data
types of all ports whose data types are not set.
If the block does not implement this method and Simulink cannot determine
the data types of any of its ports, Simulink sets the data types of all the ports
to double. If the block does not implement this method and Simulink cannot
determine the data types of some, but not all, of its ports, Simulink sets the
unknown ports to the data type of the port whose data type has the largest size.
Languages C
See Also ssSetOutputPortDataType, ssSetInputPortDataType
9-20
mdlSetDefaultPortDataTypes
9mdlSetDefaultPortDataTypes
Purpose Set the data types of ports whose data types cannot be determined from block
connectivity.
Syntax void mdlSetDefaultPortDataTypes(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Simulink invokes this method if the block has ports whose numeric types
cannot be determined from connectivity. (This usually happens when the block
is unconnected or is part of a feedback loop.) This method must set the numeric
types of all ports whose numeric types are not set.
If the block does not implement this method and at least one port is known to
be complex, Simulink sets the unknown ports to COMPLEX_YES; otherwise, it
sets the unknown ports to COMPLEX_NO.
Languages C
See Also ssSetOutputPortComplexSignal, ssSetInputPortComplexSignal
9-21
mdlSetDefaultPortDimensionInfo
9mdlSetDefaultPortDimensionInfo
Purpose Set the default dimensions of the signals accepted or emitted by an S-function’s
ports.
Syntax void mdlSetDefaultPortDimensionInfo(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
Description Simulink calls this method during signal dimension propagation when a model
does not supply enough information to determine the dimensionality of signals
that can enter or leave the block represented by S. This method should set the
dimensions of any input and output ports that are dynamically sized to default
values. If S does not implement this method, Simulink sets the dimensions of
dynamically sized ports for which dimension information is unavailable to
scalar, i.e., 1-D signals containing one element.
Example See matlabroot/simulink/src/sfun_matadd.c for an example of how to use
this function.
Languages C
See Also ssSetOutputPortMatrixDimensions, ssSetErrorStatus
9-22
mdlSetInputPortComplexSignal
9mdlSetInputPortComplexSignal
Purpose Set the numeric types (real, complex, or inherited) of the signals accepted by
an input port.
Syntax void mdlSetInputPortDataType(SimStruct *S, int_T port, CSignal_T
csig)
Arguments S
SimStruct representing an S-Function block.
port
Index of a port.
csig
Numeric type of signal.
Description Simulink calls this routine to set the input port signal type. The S-function
must check whether the specified signal type is a valid type for the specified
port. If it is valid, the S-function must set the signal type of the specified input
port. Otherwise, it must report an error using ssSetErrorStatus. The
S-function can also set the signal types of other input and output ports with
unknown signal types. Simulink reports an error if the S-function changes the
signal type of a port whose signal type is known.
If the S-function does not implement this routine, Simulink assumes that the
S-function accepts a real or complex signal and sets the input port signal type
to the specified value.
Languages C
See Also ssSetInputPortComplexSignal, ssSetErrorStatus
9-23
mdlSetInputPortDataType
9mdlSetInputPortDataType
Purpose Set the data types of the signals accepted by an input port.
Syntax void mdlSetInputPortDataType(SimStruct *S, int_T port, DTypeId id)
Arguments S
SimStruct representing an S-Function block.
port
Index of a port.
id
Data type ID.
Description Simulink calls this routine to set the data type of port. The S-function must
check whether the specified data type is a valid data type for the specified port.
If it is a valid data type, it must set the data type of the input port. Otherwise,
it must report an error using ssSetErrorStatus.
The S-function can also set the data types of other input and output ports if
they are unknown. Simulink reports an error if the S-function changes the data
type of a port whose data type has been set.
If the block does not implement this routine, Simulink assumes that the block
accepts any data type and sets the input port data type to the specified value.
Languages C
See Also ssSetInputPortDataType, ssSetErrorStatus
9-24
mdlSetInputPortDimensionInfo
9mdlSetInputPortDimensionInfo
Purpose Set the dimensions of the signals accepted by an input port.
Syntax void mdlSetInputPortDimensionInfo(SimStruct *S, int_T port,
const DimsInfo_T *dimsInfo)
Arguments S
SimStruct representing an S-Function block.
port
Index of a port.
dimsInfo
Structure that specifies the signal dimensions supported by port.
See ssSetInputPortDimensionInfo for a description of this structure.
Description Simulink calls this method during dimension propagation with candidate
dimensions dimsInfo for port. If the proposed dimensions are acceptable, this
method should go ahead and set the actual port dimensions, using
ssSetInputPortDimensionInfo. If they are unacceptable, this method should
generate an error via ssSetErrorStatus.
Note This method can set the dimensions of any other input or output port
whose dimensions derive from the dimensions of port.
By default, Simulink calls this method only if it can fully determine the
dimensionality of port from the port to which it is connected. If it cannot
completely determine the dimensionality from port connectivity, it invokes
mdlSetDefaultPortDimensionInfo. If an S-function can fully determine the
port dimensionality from partial information, the function should set the
option SS_OPTION_ALLOW_PARTIAL_DIMENSIONS_CALL in mdlInitializeSizes,
using ssSetOptions. If this option is set, Simulink invokes
mdlSetInputPortDimensionInfo even if it can only partially determine the
dimensionality of the input port from connectivity.
Languages C
Example See matlabroot/simulink/src/sfun_matadd.c for an example of how to use
this function.
9-25
mdlSetInputPortDimensionInfo
See Also ssSetErrorStatus
9-26
mdlSetInputPortFrameData
9mdlSetInputPortFrameData
Purpose Set frame data entering an input port.
Syntax void mdlSetInputPortFrameData(SimStruct *S, int_T port,
Frame_T frameData)
Arguments S
SimStruct representing an S-Function block.
port
Index of a port.
frameData
Frame data.
Description This method is called with the candidate frame setting (FRAME_YES or
FRAME_NO) for an input port. If the proposed setting is acceptable, the method
should go ahead and set the actual frame data setting using
ssSetInputPortFrameData. If the setting is unacceptable, an error should be
generated via ssSetErrorStatus. Note that any other dynamic frame input or
output ports whose frame data settings are implicitly defined by virtue of
knowing the frame data setting of the given port can also have their frame data
settings set via calls to ssSetInputPortFrameData and
ssSetOutputPortFrameData.
Languages C
See Also ssSetInputPortFrameData, ssSetOutputPortFrameData, ssSetErrorStatus
9-27
mdlSetInputPortSampleTime
9mdlSetInputPortSampleTime
Purpose Set the sample time of an input port that inherits its sample time from the port
to which it is connected.
Syntax void mdlSetInputPortSampleTime(SimStruct *S, int_T port,
real_T sampleTime, real_T offsetTime)
Arguments S
SimStruct representing an S-Function block.
port
Index of a port.
sampleTime
Inherited sample time for port.
offsetTime
Inherited offset time for port.
Description Simulink invokes this method with the sample time that port inherits from the
port to which it is connected. If the inherited sample time is acceptable, this
method should set the sample time of port to the inherited time, using
ssSetInputPortSampleTime. If the sample time is unacceptable, this method
should generate an error via ssSetErrorStatus. Note that any other inherited
input or output ports whose sample times are implicitly defined by virtue of
knowing the sample time of the given port can also have their sample times set
via calls to ssSetInputPortSampleTime or ssSetOutputPortSampleTime.
When inherited port-based sample times are specified, the sample time is
guaranteed to be one of the following.
where 0.0 < period < inf and 0.0 <= offset < period. Constant, triggered,
and variable step sample times are not propagated to S-functions with port-
based sample times.
Generally mdlSetInputPortSampleTime is called once with the input port
sample time. However, there can be cases where this function is called more
Sample Time Offset Time
Continuous 0.0 0.0
Discrete period offset
9-28
mdlSetInputPortSampleTime
than once. This happens when the simulation engine is converting continuous
sample times to continuous but fixed in minor steps sample times. When this
occurs, the original values of the sample times specified in
mdlInitializeSizes are restored before this method is called again.
The final sample time specified at the port can be different from (but equivalent
to) the sample time specified by this method. This occurs when
The model uses a fixed-step solver and the port has a continuous but fixed in
minor step sample time. In this case, Simulink converts the sample time to
the fundamental sample time for the model.
Simulink adjusts the sample time to be as numerically sound as possible. For
example, Simulink converts [0.2499999999999, 0] to [0.25, 0].
The S-function can examine the final sample times in
mdlInitializeSampleTimes.
Languages C
See Also ssSetInputPortSampleTime, ssSetOutputPortSampleTime,
mdlInitializeSampleTimes
9-29
mdlSetInputPortWidth
9mdlSetInputPortWidth
Purpose Set the width of an input port that accepts 1-D (vector) signals.
Syntax void mdlSetInputPortWidth(SimStruct *S, int_T port, int_T width)
Arguments S
SimStruct representing an S-Function block.
port
Index of a port.
width
Width of signal.
Description This method is called with the candidate width for a dynamically sized port. If
the proposed width is acceptable, the method should go ahead and set the
actual port width using ssSetInputPortWidth. If the size is unacceptable, an
error should be generated via ssSetErrorStatus. Note that any other
dynamically sized input or output ports whose widths are implicitly defined by
virtue of knowing the width of the given port can also have their widths set via
calls to ssSetInputPortWidth or ssSetOutputPortWidth.
Languages C
See Also ssSetInputPortWidth, ssSetOutputPortWidth, ssSetErrorStatus
9-30
mdlSetOutputPortComplexSignal
9mdlSetOutputPortComplexSignal
Purpose Set the numeric types (real, complex, or inherited) of the signals accepted by
an output port.
Syntax void mdlSetOutputPortDataType(SimStruct *S, int_T port, CSignal_T
csig)
Arguments S
SimStruct representing an S-Function block.
port
Index of a port.
csig
Numeric type of signal.
Description Simulink calls this routine to set the output port signal type. The S-function
must check whether the specified signal type is a valid type for the specified
port. If it is valid, the S-function must set the signal type of the specified output
port. Otherwise, it must report an error, using ssSetErrorStatus. The
S-function can also set the signal types of other input and output ports with
unknown signal types. Simulink reports an error if the S-function changes the
signal type of a port whose signal type is known.
If the S-function does not implement this routine, Simulink assumes that the
S-function accepts a real or complex signal and sets the output port signal type
to the specified value.
Languages C
See Also ssSetOutputPortComplexSignal, ssSetErrorStatus
9-31
mdlSetOutputPortDataType
9mdlSetOutputPortDataType
Purpose Set the data type of the signals emitted by an output port.
Syntax void mdlSetOutputPortDataType(SimStruct *S, int_T port, DTypeId id)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
id
Data type ID.
Description Simulink calls this routine to set the data type of port. The S-function must
check whether the specified data type is a valid data type for the specified port.
If it is a valid data type, it must set the data type of port. Otherwise, it must
report an error, using ssSetErrorStatus.
The S-function can also set the data types of other input and output ports if
their data types have not been set. Simulink reports an error if the S-function
changes the data type of a port whose data type has been set.
If the block does not implement this method, Simulink assumes that the block
accepts any data type and sets the input port data type to the specified value.
Languages C
See Also ssSetOutputPortDataType, ssSetErrorStatus
9-32
mdlSetOutputPortDimensionInfo
9mdlSetOutputPortDimensionInfo
Purpose Set the dimensions of the signals accepted by an output port.
Syntax void mdlSetOutputPortDimensionInfo(SimStruct *S, int_T port, const
DimsInfo_T *dimsInfo)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of a port.
dimsInfo
Structure that specifies the signal dimensions supported by port.
See ssSetInputPortDimensionInfo for a description of this structure.
Description Simulink calls this method with candidate dimensions dimsInfo for port. If
the proposed dimensions are acceptable, this method should go ahead and set
the actual port dimensions, using ssSetOutputPortDimensionInfo. If they are
unacceptable, this method should generate an error via ssSetErrorStatus.
Note This method can set the dimensions of any other input or output port
whose dimensions derive from the dimensions of port.
By default, Simulink calls this method only if it can fully determine the
dimensionality of port from the port to which it is connected. If it cannot
completely determine the dimensionality from port connectivity, it invokes
mdlSetDefaultPortDimensionInfo. If an S-function can fully determine the
port dimensionality from partial information, the function should set the
option SS_OPTION_ALLOW_PARTIAL_DIMENSIONS_CALL in mdlInitializeSizes,
using ssSetOptions. If this option is set, Simulink invokes
mdlSetOutputPortDimensionInfo even if it can only partially determine the
dimensionality of the input port from connectivity.
Languages C
Example See matlabroot/simulink/src/sfun_matadd.c for an example of how to use
this function.
9-33
mdlSetOutputPortDimensionInfo
See Also ssSetOutputPortDimensionInfo, ssSetErrorStatus
9-34
mdlSetOutputPortSampleTime
9mdlSetOutputPortSampleTime
Purpose Set the sample time of an output port that inherits its sample time from the
port to which it is connected.
Syntax void mdlSetOutputPortSampleTime(SimStruct *S, int_T port,
real_T sampleTime, real_T offsetTime)
Arguments S
SimStruct representing an S-Function block.
port
Index of a port.
sampleTime
Inherited sample time for port.
offsetTime
Inherited offset time for port.
Description Simulink calls this method with the sample time that port inherits from the
port to which it is connected. If the inherited sample time is acceptable, this
method should set the sample time of port to the inherited sample time, using
ssSetOutputPortSampleTime. If the inherited sample time is unacceptable,
this method should generate an error via ssSetErrorStatus. Note that this
method can set the sample time of any other input or output port whose sample
time derives from the sample time of port, using ssSetInputPortSampleTime
or ssSetOutputPortSampleTime.
Normally, sample times are propagated forward; however, if sources feeding
this block have inherited sample times, Simulink might choose to
back-propagate known sample times to this block. When back-propagating
sample times, we call this method in succession for all inherited output port
signals.
See mdlSetInputPortSampleTime for more information about when this
method is called.
Languages C
See Also ssSetOutputPortSampleTime, ssSetErrorStatus,
ssSetInputPortSampleTime, ssSetOutputPortSampleTime,
mdlSetInputPortSampleTime
9-35
mdlSetOutputPortWidth
9mdlSetOutputPortWidth
Purpose Set the width of an output port that outputs 1-D (vector) signals.
Syntax void mdlSetOutputPortWidth(SimStruct *S, int_T port, int_T width)
Arguments S
SimStruct representing an S-Function block.
port
Index of a port.
width
Width of signal.
Description This method is called with the candidate width for a dynamically sized port. If
the proposed width is acceptable, the method should go ahead and set the
actual port width, using ssSetOutputPortWidth. If the size is unacceptable, an
error should be generated via ssSetErrorStatus. Note that any other
dynamically sized input or output ports whose widths are implicitly defined by
virtue of knowing the width of the given port can also have their widths set via
calls to ssSetInputPortWidth or ssSetOutputPortWidth.
Languages C
See Also ssSetInputPortWidth, ssSetOutputPortWidth, ssSetErrorStatus
9-36
mdlSetWorkWidths
9mdlSetWorkWidths
Purpose Specify the sizes of the work vectors and create the run-time parameters
required by this S-function.
Syntax void mdlSetWorkWidths(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Simulink calls this optional method to enable this S-function to set the sizes of
state and work vectors that it needs to store global data and to create run-time
parameters (see “Run-Time Parameters” on page 7-5). Simulink invokes this
method after it has determined the input port width, output port width, and
sample times of the S-function. This allows the S-function to size the state and
work vectors based on the number and sizes of inputs and outputs and/or the
number of sample times. This method specifies the state and work vector sizes
via the macros ssGetNumContStates, ssSetNumDiscStates, ssSetNumRWork,
ssSetNumIWork, ssSetNumPWork, ssSetNumModes, and
ssSetNumNonsampledZCs.
The S-function needs to implement this method only if it does not know the
sizes of all the work vectors it requires when Simulink invokes the function’s
mdlInitializeSizes method. If this S-function implements
mdlSetWorkWidths, it should initialize the sizes of any work vectors that it
needs to DYNAMICALLY_SIZED in mdlInitializeSizes, even for those whose
exact size it knows at that point. The S-function should then specify the actual
size in mdlSetWorkWidths.
Languages Ada, C
See Also mdlInitializeSizes
9-37
mdlStart
9mdlStart
Purpose Initialize the state vectors of this S-function.
Syntax void mdlStart(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Simulink invokes this optional method at the beginning of a simulation. It
should initialize the continuous and discrete states, if any, of this S-Function
block. Use ssGetContStates and/or ssGetDiscStates to get the states. This
method can also perform any other initialization activities that this S-function
requires.
Languages Ada, C
See Also mdlInitializeConditions, ssGetContStates, ssGetDiscStates
9-38
mdlTerminate
9mdlTerminate
Purpose Perform any actions required at termination of the simulation.
Syntax void mdlTerminate(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description This method should perform any actions, such as freeing memory, that must be
performed at the end of simulation or when an S-Function block is destroyed
(e.g., when it is deleted from a model). The option
SS_OPTION_CALL_TERMINATE_ON_EXIT (see ssSetOptions) determines whether
Simulink invokes this method. If this option is not set, Simulink invokes
mdlTerminate at the end of simulation only if the mdlStart method of at least
one block in the model has executed during simulation. If this option is set,
Simulink always invokes the mdlTerminate method at the end of a simulation
run and whenever it destroys a block.
Languages Ada, C, M
Example Suppose your S-function allocates blocks of memory in mdlStart and saves
pointers to the blocks in a PWork vector. The following code fragment would free
this memory.
{
int i;
for (i = 0; i<ssGetNumPWork(S); i++) {
if (ssGetPWorkValue(S,i) != NULL) {
free(ssGetPWorkValue(S,i));
}
}
}
9-39
mdlUpdate
9mdlUpdate
Purpose Update a block’s states.
Syntax void mdlUpdate(SimStruct *S, int_T tid)
Arguments S
SimStruct representing an S-Function block.
tid
Task ID.
Description Simulink invokes this optional method at each major simulation time step. The
method should compute the S-function’s states at the current time step and
store the states in the S-function’s state vector. The method can also perform
any other tasks that the S-function needs to perform at each major time step.
Use this code if your S-function has one or more discrete states or does not have
direct feedthrough.
The reason for this is that most S-functions that do not have discrete states but
do have direct feedthrough do not have update functions. Therefore, Simulink
is able to eliminate the need for the extra call in these circumstances.
If your S-function needs to have its mdlUpdate routine called and it does not
satisfy either of the above two conditions, specify that it has a discrete state,
using the ssSetNumDiscStates macro in the mdlInitializeSizes function.
The tid (task ID) argument specifies the task running when the mdlOutputs
routine is invoked. You can use this argument in the mdlUpdate routine of a
multirate S-Function block to encapsulate task-specific blocks of code (see
“Multirate S-Function Blocks” on page 7-23).
Example For an example, see matlabroot/simulink/src/dsfunc.c.
Languages Ada, C, M
See Also mdlDerivatives, ssGetContStates, ssGetDiscStates
9-40
mdlZeroCrossings
9mdlZeroCrossings
Purpose Update zero-crossing vector.
Syntax void mdlZeroCrossings(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description An S-function needs to provide this optional method only if it does zero-crossing
detection. This method should update the S-function’s zero-crossing vector,
using ssGetNonsampledZCs.
You can use the optional mdlZeroCrossings routine when your S-function has
registered the CONTINUOUS_SAMPLE_TIME and has nonsampled zero crossings
(ssGetNumNonsampledZCs(S) > 0). The mdlZeroCrossings routine is used to
provide Simulink with signals that are to be tracked for zero crossings. These
are typically
Continuous signals entering the S-function
Internally generated signals that cross zero when a discontinuity would
normally occur in mdlOutputs
Thus, the zero-crossing signals are used to locate the discontinuities and end
the current time step at the point of the zero crossing. To provide Simulink with
zero-crossing signals, mdlZeroCrossings updates the ssGetNonsampleZCs(S)
vector.
Example See matlabroot/simulink/src/sfun_zc.c.
Languages C
See Also mdlInitializeSizes, ssGetNonsampledZCs
9-41
mdlZeroCrossings
9-42
10
SimStruct Functions
This sections describes SimStruct macros and functions.
Introduction (p. 10-2) Overview of SimStruct macros and functions.
SimStruct Macros and Functions
Listed by Usage (p. 10-3)
SimStruct macros and functions listed by usage.
Macro Reference (p. 10-22) Descriptions of the SimStruct macros and functions.
10 SimStruct Functions
10-2
Introduction
Simulink provides a set of functions for accessing the fields of an S-function’s
simulation data structure (SimStruct). S-function callback methods use these
functions to store and retrieve information about an S-function.
This reference describes the syntax and usage of each SimStruct function. The
descriptions appear alphabetically by name to facilitate location of a particular
macro. This section also provides listings of functions by usage to speed
location of macros for specific purposes, such as implementing data type
support.
Language Support
Some SimStruct functions are available only in some of the languages
supported by Simulink. The reference page for each SimStruct function lists
the languages in which it is available. If the SimStruct function is available in
C, the reference page gives its C syntax. Otherwise, it gives its syntax in the
language in which it is available.
Note Most SimStruct functions available in C are implemented as C macros.
The SimStruct
The file matlabroot/simulink/include/simstruc.h is a C language header
file that defines the Simulink data structure and the SimStruct access macros.
It encapsulates all the data relating to the model or S-function, including block
parameters and outputs.
There is one SimStruct data structure allocated for the Simulink model. Each
S-function in the model has its own SimStruct associated with it. The
organization of these SimStructs is much like a directory tree. The SimStruct
associated with the model is the root SimStruct. The SimStructs associated
with the S-functions are the child SimStructs.
SimStruct Macros and Functions Listed by Usage
SimStruct Macros and Functions Listed by Usage
This section groups SimStruct macros by usage.
Miscellaneous
Error Handling and Status
Macro Description
ssCallExternalModeFcn Invoke the external mode function for an
S-function.
ssGetModelName Get the name of an S-Function block or
model containing the S-function.
ssGetParentSS Get the parent of an S-function.
ssGetPath Get the path of an S-function or the model
containing the S-function.
ssGetRootSS Return the root (model) SimStruct.
ssGetUserData Access user data.
ssSetExternalModeFcn Specify the external mode function for an
S-function.
ssSetOptions Set various simulation options.
ssSetPlacementGroup Specify the execution order of a sink or
source S-function.
ssSetUserData Specify user data.
Macros Description
ssGetErrorStatus Get a string that identifies the last error.
ssPrintf Print a variable-content msg.
10-3
10 SimStruct Functions
10-4
I/O Port
ssSetErrorStatus Report errors.
ssWarning Display a warning message.
Macro Description
ssGetInputPortBufferDstPort Determine the output port that is
overwriting an input port’s memory
buffer.
ssGetInputPortComplexSignal Get the numeric type (complex or
real) of an input port.
ssGetInputPortConnected Determine whether an S-Function
block port is connected to a
nonvirtual block.
ssGetInputPortDataType Get the data type of an input port.
ssGetInputPortDimensions Get the dimensions of the signal
accepted by an input port.
ssGetInputPortDirectFeedThrough Determine whether an input port has
direct feedthrough.
ssGetInputPortFrameData Determine whether a port accepts
signal frames.
ssGetInputPortNumDimensions Get the dimensionality of the signals
accepted by an input port.
ssGetInputPortOffsetTime Determine the offset time of an input
port.
ssGetInputPortOverWritable Determine whether an input port can
be overwritten.
Macros Description
SimStruct Macros and Functions Listed by Usage
ssGetInputPortRealSignal Get the address of a real, contiguous
signal entering an input port.
ssGetInputPortRealSignalPtrs Access the signal elements connected
to an input port.
ssGetInputPortRequiredContiguous Determine whether the signal
elements entering a port must be
contiguous.
ssGetInputPortReusable Determine whether memory allocated
to the input port is reusable.
ssGetInputPortSampleTime Determine the sample time of an
input port.
ssGetInputPortSampleTimeIndex Get the sample time index of an input
port.
ssGetInputPortSignal Get the address of a contiguous signal
entering an input port.
ssGetInputPortSignalAddress Get the address of an input port’s
signal (Ada only).
ssGetInputPortSignalPtrs Get pointers to input signal elements
of type other than double.
ssGetInputPortWidth Determine the width of an input port.
ssGetNumInputPorts Determine how many input ports a
block has.
ssGetNumOutputPorts Can be used in any routine (except
mdlInitializeSizes) to determine
how many output ports you have set.
ssGetOutputPortBeingMerged Determine whether the output of this
block is connected to a Merge block.
Macro Description
10-5
10 SimStruct Functions
10-6
ssGetOutputPortComplexSignal Get the numeric type (complex or
real) of an output port
ssGetOutputPortDataType Get the data type of an output port.
ssGetOutputPortDimensions Get the dimensions of the signal
leaving an output port.
ssGetOutputPortFrameData Determine whether a port outputs
signal frames.
ssGetOutputPortNumDimensions Get the number of dimensions of an
output port.
ssGetOutputPortOffsetTime Determine the offset time of an
output port.
ssGetOutputPortRealSignal Access the elements of a signal
connected to an output port.
ssGetOutputPortReusable Determine whether memory
allocated to the output port is
reusable
ssGetOutputPortSampleTime Determine the sample time of an
output port.
ssGetOutputPortSignal Get the vector of signal elements
emitted by an output port.
ssGetOutputPortSignalAddress Get address of an output port’s signal
(Ada only).
ssGetOutputPortWidth Determine the width of an output
port.
ssSetInputPortComplexSignal Set the numeric type (real or
complex) of an input port.
ssSetInputPortDataType Set the data type of an input port.
Macro Description
SimStruct Macros and Functions Listed by Usage
ssSetInputPortDimensionInfo Set the dimensionality of an input
port.
ssSetInputPortDirectFeedThrough Specify that an input port is a
direct-feedthrough port.
ssSetInputPortFrameData Specify whether a port accepts signal
frames.
ssSetInputPortMatrixDimensions Specify dimension information for an
input port that accepts matrix
signals.
ssSetInputPortOffsetTime Specify the sample time offset for an
input port.
ssSetInputPortOverWritable Specify whether an input port is
overwritable by an output port.
ssSetInputPortRequiredContiguous Specify that the signal elements
entering a port must be contiguous.
ssSetInputPortReusable Specify whether an input port’s
memory buffer can be reused by other
signals in the model.
ssSetInputPortSampleTime Set the sample time of an input port.
ssSetInputPortSampleTimeIndex Specify the sample time index of an
input port.
ssSetInputPortVectorDimension Specify dimension information for an
input port that accepts vector signals.
ssSetInputPortWidth Set the width of an input port.
ssSetNumInputPorts Set the number of input ports on an
S-Function block.
ssSetNumOutputPorts Specify the number of output ports on
an S-Function block.
Macro Description
10-7
10 SimStruct Functions
10-8
ssSetOutputPortComplexSignal Specify the numeric type (real or
complex) of this port.
ssSetOutputPortDataType Specify the data type of an output
port.
ssSetOutputPortDimensionInfo Specify the dimensionality of an
output port.
ssSetOutputPortFrameData Specify whether a port outputs
framed data.
ssSetOutputPortMatrixDimensions Specify dimension information for an
output port that emits matrix signals
ssSetOutputPortOffsetTime Specify the sample time offset value
of an output port.
ssSetOutputPortReusable Specify whether an output port’s
memory can be reused.
ssSetOutputPortSampleTime Specify the sample time of an output
port.
ssSetOutputPortVectorDimension Specify dimension information for an
output port that emits vector signals
ssSetOutputPortWidth Specify the width of a 1-D (vector)
output port.
ssSetOutputPortMatrixDimensions Specify the dimensions of a 2-D
(matrix) signal.
ssSetOutputPortVectorDimension Specify the dimension of a 1-2
(vector) signal.
ssSetVectorMode Specify the vector mode that an
S-function supports.
Macro Description
SimStruct Macros and Functions Listed by Usage
Dialog Box Parameters
These macros enable an S-function to access and set the tunability of
parameters that a user specifies in the S-function’s dialog box.
Macro Description
ssGetDTypeIdFromMxArray Return the Simulink data type of a dialog
parameter.
ssGetNumParameters Get the number of parameters that this
block has (Ada only).
ssGetNumSFcnParams Get the number of parameters that an
S-function expects.
ssGetSFcnParam Get a parameter entered by a user in the
S-Function block dialog box.
ssSetNumSFcnParams Set the number of parameters that an
S-function expects.
ssSetParameterName Set the name of a parameter (Ada only).
ssSetParameterTunable Set the tunability of a parameter (Ada
only).
ssGetSFcnParamsCount Get the actual number of parameters
specified by the user.
ssSetSFcnParamNotTunable Obsolete.
ssSetSFcnParamTunable Specify the tunability of a dialog box
parameter.
10-9
10 SimStruct Functions
10-1
Run-Time Parameters
These macros allow you to create, update, and access run-time parameters
corresponding to a block’s dialog parameters.
Macro Description
ssRegDlgParamAsRunTimePa
ram
Register a run-time parameter.
ssUpdateDlgParamAsRunTim
eParam
Update a run-time parameter.
ssGetNumRunTimeParams Get the number of run-time parameters
created by this S-function.
ssGetRunTimeParamInfo Get the attributes of a specified run-time
parameter.
ssRegAllTunableParamsAsR
unTimeParams
Register all tunable dialog parameters as
run-time parameters.
ssSetNumRunTimeParams Specify the number of run-time parameters
to be created by this S-function.
ssSetRunTimeParamInfo Specify the attributes of a specified
run-time parameter.
ssUpdateAllTunableParams
AsRunTimeParams
Update all run-time parameters
corresponding to tunable dialog
parameters.
ssUpdateRunTimeParamData Update the value of a specified run-time
parameter.
ssUpdateRunTimeParamInfo Update the attributes of a specified
run-time parameter from the attributes of
the corresponding dialog parameters.
0
SimStruct Macros and Functions Listed by Usage
Sample Time
Macro Description
ssGetSampleTimeOffset Get the offset of the current sample time
(Ada only).
ssGetSampleTimePeriod Get the period of the current sample time
(Ada only).
ssGetTNext Get the time of the next sample hit in a
discrete S-function with a variable sample
time.
ssGetNumSampleTimes Get the number of sample times an
S-function has.
ssGetPortBasedSampleTime
BlockIsTriggered
Determine whether a block that uses
port-based sample times resides in a
triggered subsystem.
ssIsContinuousTask Determine whether a specified rate is the
continuous rate.
ssIsSampleHit Determine the sample rate at which an
S-function is operating.
ssIsSpecialSampleHit Determine whether the current sample
time hits two specified rates.
ssSampleAndOffsetAreTrig
gered
Determine whether a sample time and
offset value pair indicate a triggered
sample time.
ssSetNumSampleTimes Set the number of sample times an
S-function has.
ssSetOffsetTime Specify the offset of a sample time.
10-11
10 SimStruct Functions
10-1
ssSetSampleTime Specify a sample time for an S-function.
ssSetTNext Specify the time of the next sample hit in
an S-function.
Macro Description
2
SimStruct Macros and Functions Listed by Usage
State and Work Vector
Macro Description
ssGetContStateAddress Get the address of a block’s continuous
state vector.
ssGetContStates Get an S-function’s continuous states.
ssGetDiscStates Get an S-function’s discrete states.
ssGetDWork Get a DWork vector.
ssGetDWorkComplexSignal Determine whether the elements of a data
type work vector are real or complex
numbers.
ssGetDWorkDataType Get the data type of a data type work
vector.
ssGetDWorkName Get the name of a data type work vector.
ssGetDWorkUsedAsDState Determine whether a data type work vector
is used as a discrete state vector.
ssGetDWorkWidth Get the size of a data type work vector.
ssGetdX Get the derivatives of the continuous states
of an S-function.
ssGetIWork Get an S-function’s integer-valued (int_T)
work vector.
ssGetIWorkValue Get a value from a block’s integer work
vector.
ssGetModeVector Get an S-function’s mode work vector.
ssGetModeVectorValue Get an element of a block’s mode vector.
ssGetNonsampledZCs Get an S-function’s zero-crossing signals
vector.
10-13
10 SimStruct Functions
10-1
ssGetNumContStates Determine the number of continuous states
that an S-function has.
ssGetNumDiscStates Determine the number of discrete states
that an S-function has.
ssGetNumDWork Get the number of data type work vectors
used by a block.
ssGetNumIWork Get the size of an S-function’s integer work
vector.
ssGetNumModes Determine the size of an S-function’s mode
vector.
ssGetNumNonsampledZCs Determine the number of nonsampled zero
crossings that an S-function detects.
ssGetNumPWork Determine the size of an S-function’s
pointer work vector.
ssGetNumRWork Determine the size of an S-function’s
real-valued (real_T) work vector.
ssGetPWork Get an S-function’s pointer (void *) work
vector.
ssGetPWorkValue Get a pointer from a pointer work vector.
ssGetRealDiscStates Get the real (real_T) values of an
S-function’s discrete state vector.
ssGetRWork Get an S-function’s real-valued (real_T)
work vector.
ssGetRWorkValue Get an element of an S-function’s
real-valued work vector.
ssSetDWorkComplexSignal Specify whether the elements of a data type
work vector are real or complex.
Macro Description
4
SimStruct Macros and Functions Listed by Usage
ssSetDWorkDataType Specify the data type of a data type work
vector.
ssSetDWorkName Specify the name of a data type work
vector.
ssSetDWorkUsedAsDState Specify that a data type work vector is used
as a discrete state vector.
ssSetDWorkWidth Specify the width of a data type work
vector.
ssSetIWorkValue Set an element of a block’s integer work
vector.
ssSetModeVectorValue Set an element of a block’s mode vector.
ssSetNumContStates Specify the number of continuous states
that an S-function has.
ssSetNumDiscStates Specify the number of discrete states that
an S-function has.
ssSetNumDWork Specify the number of data type work
vectors used by a block.
ssSetNumIWork Specify the size of an S-function’s integer
(int_T) work vector.
ssSetNumModes Specify the number of operating modes that
an S-function has.
ssSetNumNonsampledZCs Specify the number of zero crossings that
an S-function detects.
ssSetNumPWork Specify the size of an S-function’s pointer
(void *) work vector.
ssSetNumRWork Specify the size of an S-function’s real
(real_T) work vector.
Macro Description
10-15
10 SimStruct Functions
10-1
ssSetPWorkValue Set an element of a block’s pointer work
vector.
ssSetRWorkValue Set an element of a block’s floating-point
work vector.
Macro Description
6
SimStruct Macros and Functions Listed by Usage
Simulation Information
Macro Description
ssGetAbsTol Get the absolute tolerances used by a
model’s variable-step solver.
ssGetBlockReduction Determine whether a block has requested
block reduction before the simulation has
begun and whether it has actually been
reduced after the simulation loop has begun
ssGetErrorStatus Get a string that identifies the last error.
ssGetInlineParameters Determine whether the user has set the
inline parameters option for the model
containing this S-function.
ssGetSimMode Determine the context in which an
S-function is being invoked: normal
simulation, external-mode simulation,
model editor, etc.
ssGetSolverMode Get the solver mode being used to solve the
S-function.
ssGetSolverName Get the name of the solver being used for
the simulation.
ssGetStateAbsTol Get the absolute tolerance used by the
model’s variable-step solver for a specified
state
ssGetStopRequested Get the value of the simulation stop
requested flag
ssGetT Get the current base simulation time.
ssGetTaskTime Get the current time for a task.
ssGetTFinal Get the end time of the current simulation.
10-17
10 SimStruct Functions
10-1
ssGetTNext Get the time of the next sample hit.
ssGetTStart Get the start time of the current
simulation.
ssIsFirstInitCond Determine whether this is the first call to
mdlInitializeConditions.
ssIsMajorTimeStep Determine whether the current time step is
a major time step.
ssIsMinorTimeStep Determine if the current time step is a
minor time step.
ssIsVariableStepSolver Determine whether the current solver is a
variable-step solver.
ssSetBlockReduction Request that Simulink attempt to reduce a
block.
ssSetSolverNeedsReset Ask Simulink to reset the solver.
ssSetStopRequested Ask Simulink to terminate the simulation
at the end of the current time step.
Macro Description
8
SimStruct Macros and Functions Listed by Usage
Function Call
Data Type
Macro Description
ssCallSystemWithTid Execute a function-call subsystem
connected to an S-function.
ssSetCallSystemOutput Specify that an output port element issues
a function call.
Macro Description
ssGetDataTypeId Get the ID for a data type.
ssGetDataTypeName Get a data type’s name.
ssGetDataTypeSize Get a data type’s size.
ssGetDataTypeZero Get the zero representation of a data type.
ssGetInputPortDataType Get the data type of an input port.
ssGetNumDataTypes Get the number of data types defined by an
S-function or the model.
ssGetOutputPortDataType Get the data type of an output port.
ssGetOutputPortSignal Get an output signal of any type except
double.
ssRegisterDataType Register a data type.
ssSetDataTypeSize Specify the size of a data type.
ssSetDataTypeZero Specify the zero representation of a data
type.
ssSetInputPortDataType Specify the data type of signals accepted by
an input port.
10-19
10 SimStruct Functions
10-2
Real-Time Workshop
Macro Description
ssGetDWorkRTWIdentifier Get the identifier used to declare a DWork
vector in code generated from the
associated S-function.
ssGetDWorkRTWStorageClas
s
Get the storage class of a DWork vector in
code generated from the associated
S-function.
ssGetDWorkRTWTypeQualifi
er
Get the C type qualifier (e.g., const) used to
declare a DWork vector in code generated
from the associated S-function.
ssGetDWorkRTWTypeQualifi
er
Set the identifier used to declare a DWork
vector in code generated from the
associated S-function.
ssGetPlacementGroup Get the name of the placement group of a
block
ssSetDWorkRTWIdentifier Set the storage class of a DWork vector in
code generated from the associated
S-function.
ssSetDWorkRTWStorageClas
s
Set the C type qualifier (e.g., const) used to
declare a DWork vector in code generated
from the associated S-function.
ssSetPlacementGroup Specify the name of the placement group of
a block.
ssWriteRTW2dMatParam Write a Simulink matrix parameter to the
S-function’s model.rtw file.
ssWriteRTWMx2dMatParam Write a MATLAB matrix parameter to the
S-function’s model.rtw file.
0
SimStruct Macros and Functions Listed by Usage
ssWriteRTWMxVectParam Write a MATLAB vector parameter to the
S-function’s model.rtw file.
ssWriteRTWParameters Write tunable parameters to the
S-function’s model.rtw file.
ssWriteRTWParamSettings Write settings for the S-function’s
parameters to the model.rtw file.
ssWriteRTWScalarParam Write a scalar parameter to the S-function’s
model.rtw file.
ssWriteRTWStr Write a string to the S-function’s model.rtw
file.
ssWriteRTWStrParam Write a string parameter to the S-function’s
model.rtw file.
ssWriteRTWStrVectParam Write a string vector parameter to the
S-function’s model.rtw file
ssWriteRTWVectParam Write a Simulink vector parameter to the
S-function’s model.rtw file.
ssWriteRTWWorkVect Write the S-function’s work vectors to the
model.rtw file.
Macro Description
10-21
10 SimStruct Functions
10-2
Macro Reference
This section contains descriptions of each SimStruct macro.
2
ssCallExternalModeFcn
10ssCallExternalModeFcn
Purpose Invoke the external mode function for an S-function.
Syntax void ssCallExternalModeFcn(SimStruct *S, SFunExtModeFcn *fcn)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
fcn
External mode function.
Description Specifies the external mode function for S.
Languages C
See Also ssSetExternalModeFcn
10-23
ssCallSystemWithTid
10ssCallSystemWithTid
Purpose Specify that an output port is issuing a function call.
Syntax ssCallSystemWithTid(SimStruct *S, port_index, tid)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port_index
Index of the port that is issuing the function call.
tid
Task ID.
Description Use in mdlOutputs to execute a function-call subsystem connected to the
S-function. The invoking syntax is
if (!ssCallSystemWithTid(S,index, tid)) {
/* Error occurred which will be reported by Simulink */
return;
}
Languages C
See Also ssSetCallSystemOutput
10-24
ssGetAbsTol
10ssGetAbsTol
Purpose Get the absolute tolerances used by a model’s variable-step solver.
Syntax real_T *ssGetAbsTol(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Use in mdlStart to get the absolute tolerances used by the variable-step solver
for this simulation. Returns a pointer to an array that contains the tolerance
for each continuous state.
Note Absolute tolerances are not allocated for fixed-step solvers. Therefore,
you should not invoke this macro until you have verified that the simulation is
using a variable-step solver, using ssIsVariableStepSolver.
Languages C, C++
Example {
int isVarSolver = ssIsVariableStepSolver(S);
if (isVarSolver) {
real_T *absTol = ssGetAbsTol(S);
int nCStates = ssGetNumContStates(S);
absTol[0] = whatever_value;
...
absTol[nCStates-1] = whatever_value;
}
}
See Also ssGetStateAbsTol, ssIsVariableStepSolver
10-25
ssGetBlockReduction
10ssGetBlockReduction
Purpose Determine whether a block has requested block reduction before the
simulation has begun and whether it has actually been reduced after the
simulation loop has begun.
Syntax unsigned int_T ssGetBlockReduction(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description The result of this function depends on when it is invoked. When invoked before
the simulation loop has started, i.e., in mdlSetWorkWidths or earlier, this macro
returns true if the block has previously requested that it be reduced. When
invoked after the simulation loop has begun, this macro returns true if the
block has actually been reduced, i.e., eliminated from the list of blocks to be
executed during the simulation loop.
Note If a block has been reduced, the only callback method invoked for the
block after the simulation loop has begun is the block’s mdlTerminate method.
Further, Simulink invokes the mdlTerminate method only if the block has set
its SS_OPTION_CALL_TERMINATE_AT_EXIT option, using ssSetOptions. Thus, if
your block needs to determine whether it has actually been reduced, it must
set the SS_OPTION_CALL_TERMINATE_AT_EXIT option before the simulation loop
has begun and invoke ssGetBlockReduction in its mdlTerminate method.
Languages C
See Also ssSetBlockReduction
10-26
ssGetContStateAddress
10ssGetContStateAddress
Purpose Get the address of a block’s continuous state vector.
Ada Syntax ssGetContStateAddress(S : in SimStruct) return System.Address
Arguments S
SimStruct representing an S-Function block.
Description Can be used in the simulation loop, mdlInitializeConditions, or mdlStart
routines to get the address of the S-function’s continuous state vector. This
vector has length ssGetNumContStates(S). Typically, this vector is initialized
in mdlInitializeConditions and used in mdlOutputs.
Languages Ada
See Also ssGetNumContStates, ssGetRealDiscStates, ssGetdX,
mdlInitializeConditions, mdlStart
10-27
ssGetContStates
10ssGetContStates
Purpose Get a block’s continuous states.
Syntax real_T *ssGetContStates(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Can be used in the simulation loop, mdlInitializeConditions, or mdlStart
routines to get the real_T continuous state vector. This vector has length
ssGetNumContStates(S). Typically, this vector is initialized in
mdlInitializeConditions and used in mdlOutputs.
Languages C
See Also ssGetNumContStates, ssGetRealDiscStates, ssGetdX,
mdlInitializeConditions, mdlStart
10-28
ssGetDataTypeId
10ssGetDataTypeId
Purpose Get the ID of a data type.
Syntax DTypeID ssGetDataTypeId(SimStruct *S, char *name)
Arguments S
SimStruct representing an S-Function block.
name
Name of a data type.
Description Returns the ID of the data type specified by name if name is a registered type
name. Otherwise, this macro returns INVALID_DTYPE_IDL and reports an error.
Because this macro reports any error that occurs, you do not need to use
ssSetErrorStatus to report the error.
Languages C
Example The following example gets the ID of the data type named Color.
int_T id = ssGetDataTypeId (S, "Color");
if(id == INVALID_DTYPE_ID) return;
See Also ssRegisterDataType
10-29
ssGetDataTypeName
10ssGetDataTypeName
Purpose Get the name of a data type.
Syntax char *ssGetDataTypeName(SimStruct *S, DTypeId id)
Arguments S
SimStruct representing an S-Function block.
id
ID of data type.
Description Returns the name of the data type specified by id, if id is valid. Otherwise, this
macro returns NULL and reports an error. Because this macro reports any error
that occurs, you do not need to use ssSetErrorStatus to report the error.
Example The following example gets the name of a custom data type.
const char *dtypeName = ssGetDataName(S, id);
if(dtypeName == NULL) return;
Languages C
See Also ssRegisterDataType
10-30
ssGetDataTypeSize
10ssGetDataTypeSize
Purpose Get the size of a custom data type.
Syntax GetDataTypeSize(SimStruct *S, DTypeId id)
Arguments S
SimStruct representing an S-Function block.
id
ID of data type.
Description Returns the size of the data type specified by id, if id is valid and the data
type’s size has been set. Otherwise, this macro returns INVALID_DTYPE_SIZE
and reports an error.
Note Because this macro reports any error that occurs when it is invoked,
you do not need to use ssSetErrorStatus to report the error.
Languages C
Example The following example gets the size of the int16 data type.
int_T size = ssGetDataTypeSize(S, SS_INT16);
if(size == INVALID_DTYPE_SIZE) return;
See Also ssSetDataTypeSize
10-31
ssGetDataTypeZero
10ssGetDataTypeZero
Purpose Get the zero representation of a data type.
Syntax void* ssGetDataTypeZero(SimStruct *S, DTypeId id)
Arguments S
SimStruct representing an S-Function block.
id
ID of data type.
Description Returns a pointer to the zero representation of the data type specified by id, if
id is valid and the data type’s size has been set. Otherwise, this macro returns
NULL and reports an error. Because this macro reports any error that occurs,
you do not need to use ssSetErrorStatus to report the error.
Languages C
Example The following example gets the zero representation of a custom data type.
const void *myZero = ssGetDataTypeZero(S, id);
if(myZero == NULL) return;
See Also ssRegisterDataType, ssSetDataTypeSize, ssSetDataTypeZero
10-32
ssGetDiscStates
10ssGetDiscStates
Purpose Get a block’s discrete states.
Syntax real_T *ssGetDiscStates(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns a block’s discrete state vector has an array of real_T elements of
length ssGetNumDiscStates(S). Typically, the state vector is initialized in
mdlInitializeConditions, updated in mdlUpdate, and used in mdlOutputs.
You can use this macro in the simulation loop, mdlInitializeConditions, or
mdlStart routines.
Languages C
See Also ssGetNumDiscStates, mdlInitializeConditions, mdlUpdate, mdlOutputs,
mdlStart
10-33
ssGetDTypeIdFromMxArray
10ssGetDTypeIdFromMxArray
Purpose Get the data type of an S-function parameter.
Syntax DTypeId ssGetDTypeIdFromMxArray(const mxArray *m)
Arguments m
MATLAB array representing the parameter.
Description Returns the data type of an S-function parameter represented by a MATLAB
array. This macro returns an enumerated type representing the data type. The
enumerated type DTypeId is defined in simstruc.h. The following table shows
the equivalency of Simulink, MATLAB, and C data types.
ssGetDTypeIdFromMxArray returns INVALID_DTYPE_ID if the mxClassId does
not map to any built-in Simulink data type ID. For example, if mxId ==
mxSTRUCT_CLASS, the return value is INVALID_DTYPE_ID. Otherwise the return
value is one of the enum values in BuiltInDTypeId. For example, if mxId ==
mxUINT16_CLASS, the return value is SS_UINT16.
Simulink Data Type
DTypeId
MATLAB Data Type
mxClassID C- Data Type
SS_DOUBLE mxDOUBLE_CLASS real_T
SS_SINGLE mxSINGLE_CLASS real32_T
SS_INT8 mxINT8_CLASS int8_T
SS_UINT8 mxUINT8_CLASS uint8_T
SS_INT16 mxINT16_CLASS int16_T
SS_UINT16 mxUINT16_CLASS uint16_T
SS_INT32 mxINT32_CLASS int32_T
SS_UINT32 mxUINT32_CLASS uint32_T
SS_BOOLEAN mxUINT8_CLASS+ logical boolean_T
10-34
ssGetDTypeIdFromMxArray
Note Use ssGetSFcnParam to get the array representing the parameter.
Example See the example in matlabroot/simulink/src/sfun_dtype_param.c to learn
how to use data typed parameters in an S-function.
Languages C
See Also ssGetSFcnParam
10-35
ssGetDWork
10ssGetDWork
Purpose Get a DWork vector.
Syntax void *ssGetDWork(SimStruct *S, int_T vector)
Arguments S
SimStruct representing an S-Function block.
vector
Index of a data type work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
Description Returns a pointer to the specified vector.
Languages C, C++
See Also ssSetNumDWork
10-36
ssGetDWorkComplexSignal
10ssGetDWorkComplexSignal
Purpose Determine whether the elements of a data type work vector are real or complex
numbers.
Syntax CSignal_T ssGetDWorkComplexSignal(SimStruct *S, int_T vector)
Arguments S
SimStruct representing an S-Function block.
vector
Index of a data type work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
Description Returns COMPLEX_YES if the specified vector contains complex numbers;
otherwise, COMPLEX_NO.
Languages C, C++
See Also ssSetDWorkComplexSignal
10-37
ssGetDWorkDataType
10ssGetDWorkDataType
Purpose Get the data type of a data type work vector.
Syntax DTypeId ssGetDWorkDataType(SimStruct *S, int_T vector)
Arguments S
SimStruct representing an S-Function block.
vector
Index of a data type work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
Description Returns the data type of the specified data type work vector.
Languages C, C++
See Also ssSetDWorkDataType
10-38
ssGetDWorkName
10ssGetDWorkName
Purpose Get the name of a data type work vector.
Syntax char_T *ssGetDWorkName(SimStruct *S, int_T vector)
Arguments S
SimStruct representing an S-Function block.
vector
Index of the work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
Description Returns the name of the specified data type work vector.
Languages C, C++
See Also ssSetDWorkName
10-39
ssGetDWorkRTWIdentifier
10ssGetDWorkRTWIdentifier
Purpose Get the identifier used to declare a DWork vector in code generated from the
associated S-function.
Syntax char_T * ssGetDWorkRTWIdentifier(SimStruct* S, int idx)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
Description Returns the identifier used in code generated by the Real-Time Workshop to
declare the DWork vector specified by idx.
Languages C, C++
See Also ssSetDWorkRTWIdentifier
10-40
ssGetDWorkRTWStorageClass
10ssGetDWorkRTWStorageClass
Purpose Get the storage class of a DWork vector in code generated from the associated
S-function.
Syntax ssRTWStorageType ssGetDWorkRTWStorageClass(SimStruct* S, int idx)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
Description Returns the storage class of the the DWork vector specified by idx. The storage
class is a code-generation attribute that determines how the code generated by
the Real-Time Workshop for this S-function allocates memory for this work
vector (see “Signal Storage Concepts” in the online documentation for the
Real-Time Workshop). The returned storage class specifier is a value of type
ssRTWStorageType:
typedef enum {
SS_RTW_STORAGE_AUTO = 0,
SS_RTW_STORAGE_EXPORTED_GLOBAL,
SS_RTW_STORAGE_IMPORTED_EXTERN,
SS_RTW_STORAGE_IMPORTED_EXTERN_POINTER
} ssRTWStorageType;
Languages C, C++
See Also ssSetDWorkRTWStorageClass
10-41
ssGetDWorkRTWTypeQualifier
10ssGetDWorkRTWTypeQualifier
Purpose Get the C type qualifier (e.g., const) used to declare a DWork vector in code
generated from the associated S-function.
Syntax char_T * ssGetDWorkRTWTypeQualifier(SimStruct* S, int idx)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
Description Returns the C type qualifier (e.g., const) used to declare the DWork vector
specified by idx in code generated by the Real-Time Workshop from the
associated S-function.
Languages C, C++
See Also ssSetDWorkRTWTypeQualifier
10-42
ssGetDWorkUsedAsDState
10ssGetDWorkUsedAsDState
Purpose Determine whether a data type work vector is used as a discrete state vector.
Syntax int_T ssGetDWorkUsedAsDState(SimStruct *S, int_T vector)
Arguments S
SimStruct representing an S-Function block.
vector
Index of a data type work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
Description Returns SS_DWORK_USED_AS_DSTATE if this vector is used to store a block’s
discrete states.
Languages C, C++
See Also ssSetDWorkUsedAsDState
10-43
ssGetDWorkWidth
10ssGetDWorkWidth
Purpose Get the size of a data type work vector.
Syntax int_T ssGetDWorkWidth(SimStruct *S, int_T vector)
Arguments S
SimStruct representing an S-Function block.
vector
Index of a work vector, where the index is one of 0, 1, 2, ... ssGetNumDWork(S).
Description Returns the number of elements in the specified work vector.
Languages C, C++
See Also ssSetDWorkWidth
10-44
ssGetdX
10ssGetdX
Purpose Get the derivatives of a block’s continuous states.
Syntax (real_T *) ssGetdX(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns a pointer to an array containing the continuous states of S, which can
be a block or the model. Use ssGetNumContStates(S) to get the length of the
array. Use this macro in mdlDerivatives to get the derivatives of a model or
block’s continuous states.
Note The pointer returned by this macro changes as the solver evaluates
different integration stages to compute the integral.
Languages C
See Also ssGetNumContStates, ssGetContStates
10-45
ssGetErrorStatus
10ssGetErrorStatus
Purpose Get a string that identifies the last error.
C Syntax const char_T *ssGetErrorStatus(SimStruct *S)
Ada Syntax const char_T *ssGetErrorStatus(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns a string that identifies the last error.
Languages Ada, C
See Also ssSetErrorStatus
10-46
ssGetInlineParameters
10ssGetInlineParameters
Purpose Determine whether the user has set the inline parameters option for the model
containing this S-function.
Syntax boolean_T ssGetInlineParameters(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns TRUE if the user has checked the Inline parameters option on the
Advanced pane of the Simulation parameters dialog box (see “The Advanced
Pane” in the online Simulink documentation).
Languages C
10-47
ssGetInputPortBufferDstPort
10ssGetInputPortBufferDstPort
Purpose Determine the output port that is sharing this input port’s buffer.
Syntax ssGetInputPortBufferDstPort(SimStruct *S, int_T inputPortIdx)
Arguments S
SimStruct representing an S-Function block.
inputPortIdx
Index of the port overwritten by an output port.
Description Use in any run-time S-function callback routine to determine the output port
that is overwriting the specified input port. This can be used when you have
specified the following:
The input port and some output port on an S-function are not test points
(ssSetInputPortTestPoint and ssSetOutputPortTestPoint).
The input port is overwritable (ssSetInputPortOverWritable).
If you have this set of conditions, Simulink can use the same memory buffer for
an input port and an output port. Simulink determines which ports share
memory buffers. Use this function any time after model initialization to get the
index of the output port that reuses the specified input port’s buffer. If none of
the S-function’s output ports reuse this input port buffer, this macro returns
INVALID_PORT_IDX (= -1).
Languages C
See Also ssSetNumInputPorts, ssSetInputPortOverWritable
10-48
ssGetInputPortComplexSignal
10ssGetInputPortComplexSignal
Purpose Get the numeric type (complex or real) of an input port.
Syntax DTypeId ssGetInputPortComplexSignal(SimStruct *S,input_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an input port.
Description Returns the numeric type of port.
Languages C
See Also ssSetInputPortComplexSignal
10-49
ssGetInputPortConnected
10ssGetInputPortConnected
Purpose Determine whether a port is connected to a nonvirtual block.
Syntax int_T ssGetInputPortConnected(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Port whose connection status is needed.
Description Returns true if the specified port on the block represented by S is connected to
a nonvirtual block. Can be invoked anywhere except in mdlInitializeSizes or
mdlCheckParameters. The S-function must have previously set the number of
input ports in mdlInitializeSizes, using ssSetNumInputPorts.
Languages C
See Also ssSetNumInputPorts
10-50
ssGetInputPortDataType
10ssGetInputPortDataType
Purpose Get the data type of an input port.
C Syntax DTypeId ssGetInputPortDataType(SimStruct *S,input_T port)
Ada Syntax function ssGetInputPortDataType(S : in SimStruct; port : in Integer
:= 0) return Integer;
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of an input port.
Description Returns the data type of the input port specified by port.
Languages Ada, C
See Also ssSetInputPortDataType
10-51
ssGetInputPortDimensions
10ssGetInputPortDimensions
Purpose Get the dimensions of the signal accepted by an input port.
Syntax int_T *ssGetInputPortDimensions(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an input port.
Description Returns an array of integers that specifies the dimensions of the signal
accepted by port, e.g., [4 2] for a 4-by-2 matrix array. The size of the
dimensions array is equal to the number of signal dimensions accepted by the
port, e.g., 1 for a vector signal or 2 for a matrix signal.
Languages C
See Also ssGetInputPortNumDimensions
10-52
ssGetInputPortDirectFeedThrough
10ssGetInputPortDirectFeedThrough
Purpose Determine whether a port has direct feedthrough.
C Syntax int_T ssGetInputPortDirectFeedThrough(SimStruct *S, int_T port)
Ada Syntax function ssGetInputPortDirectFeedThrough(S : in SimStruct;
port : in Integer := 0) return Boolean;
Arguments S
SimStruct representing an S-Function block.
port
Index of the port whose direct feedthrough property is required.
Description Use in any routine (except mdlInitializeSizes) to determine whether an
input port has direct feedthrough.
Languages Ada, C
See Also ssSetInputPortDirectFeedThrough
10-53
ssGetInputPortFrameData
10ssGetInputPortFrameData
Purpose Determine whether a port accepts signal frames.
Syntax int_T ssGetInputPortFrameData(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an input port.
Description Returns one of the following:
-1
Port accepts either frame or unframed input.
0
Port accepts unframed input only.
1
Port accepts frame input only.
Languages C
See Also ssSetInputPortFrameData, mdlSetInputPortFrameData
10-54
ssGetInputPortNumDimensions
10ssGetInputPortNumDimensions
Purpose Get the dimensionality of the signals accepted by an input port.
Syntax int_T ssGetInputPortNumDimensions(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an input port.
Description Returns the number of dimensions of port or DYNAMICALLY_SIZED, if the
number of dimensions is unknown.
Languages C
See Also ssGetInputPortDimensions
10-55
ssGetInputPortOffsetTime
10ssGetInputPortOffsetTime
Purpose Get the offset time of an input port.
Syntax ssGetInputPortOffsetTime(SimStruct *S,inputPortIdx)
Arguments S
SimStruct representing an S-Function block.
inputPortIdx
Index of the port whose offset time is required.
Description Use in any routine (except mdlInitializeSizes) to determine the offset time
of an input port. This should only be used if you have specified the sample times
as port-based.
Languages C
See Also ssSetInputPortOffsetTime, ssGetInputPortSampleTime
10-56
ssGetInputPortOverWritable
10ssGetInputPortOverWritable
Purpose Determine whether an input port can be overwritten.
C Syntax int_T ssGetInputPortOverWritable(SimStruct *S, int_T port)
Ada Syntax function ssGetInputPortOverWritable(S : in SimStruct; port : in
Integer := 0) return Boolean;
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of the input port whose overwritability is being set.
Description Returns true if the input port can be overwritten.
Languages Ada, C
See Also ssSetInputPortOverWritable
10-57
ssGetInputPortRealSignal
10ssGetInputPortRealSignal
Purpose Get the address of a real, contiguous signal entering an input port.
Syntax const real_T *ssGetInputPortRealSignal(SimStruct *S, inputPortIdx)
Arguments S
SimStruct representing an S-Function block.
inputPortIdx
Index of the port whose sample time is required.
Description Returns the address of a real signal on the specified input port. A method
should use this macro only if the input signal is known to be real and
mdlInitializeSizes has specified that the elements of the input signal be
contiguous, using ssSetInputPortRequiredContiguous.
Languages C, C++
Example The following code demonstrates the use of ssGetInputPortRealSignal.
Set flags to require that the input ports be contiguous:
void mdlInitializeSizes(SimStruct* S) {
int_T i;
/* snip */
if (!ssSetNumInputPorts(S,2)) return;
for (i = 0; i < 2; i++) {
/* snip */
ssSetInputPortDirectFeedThrough(S,i,1);
ssSetInputPortRequiredContiguous(S,i,1);
}
/* snip */
}
You can now use ssGetInputPortRealSignal in mdlOutputs:
void mdlOutputs(SimStruct* S, int_T tid) {
int_T i;
/* snip */
for (i = 0; i < 2; i++) {
10-58
ssGetInputPortRealSignal
int_T nu = ssGetInputPortWidth(S,i);
const real_T* u = ssGetInputPortRealSignal(S,i);
UseInputVectorInSomeFunction(u, nu);
}
/* snip */
}
See Also ssSetInputPortRequiredContiguous, ssGetInputPortSignal,
mdlInitializeSizes
10-59
ssGetInputPortRealSignalPtrs
10ssGetInputPortRealSignalPtrs
Purpose Get pointers to signals of type double connected to an input port.
Syntax InputRealPtrsType ssGetInputPortRealSignalPtrs(SimStruct *S, int_T
port)
Arguments S
SimStruct representing an S-Function block.
port
Index of port whose signal is required.
Description Returns pointers to the elements of a signal of type double connected to port.
The input port index starts at 0 and ends at the number of input ports minus
1. This macro returns a pointer to an array of pointers to the real_T input
signal elements. The length of the array of pointers is equal to the width of the
input port.
Languages C
Example The following example reads all input port signals.
int_T i,j;
int_T nInputPorts = ssGetNumInputPorts(S);
for (i = 0; i < nInputPorts; i++) {
InputRealPtrsType uPtrs =
ssGetInputPortRealSignal(S,i);
int_T nu = ssGetInputPortWidth(S,i);
for (j = 0; j < nu; j++) {
SomeFunctionToUseInputSignalElement(*uPtrs
[j]);
}
}
See Also ssGetInputPortWidth, ssGetInputPortDataType,
ssGetInputPortSignalPtrs
10-60
ssGetInputPortRequiredContiguous
10ssGetInputPortRequiredContiguous
Purpose Determine whether the signal elements entering a port must be contiguous.
Syntax int_T ssGetInputPortRequiredContiguous(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of an input port.
Description Returns true if the signal elements entering the specified port must occupy
contiguous areas of memory. If the elements are contiguous, a method can
access the elements of the signal simply by incrementing the signal pointer
returned by ssGetInputPortSignal.
Note The default setting for this flag is false. Hence, the default method for
accessing the input signals is ssGetInputSignalPtrs.
Languages C, C++
See Also ssSetInputPortRequiredContiguous, ssGetInputPortSignal,
ssGetInputPortSignalPtrs
10-61
ssGetInputPortReusable
10ssGetInputPortReusable
Purpose Determine whether memory allocated to the input port is reusable.
Syntax int_T ssGetInputPortReusable(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of the input port.
Description Returns true if the input port memory buffer can be reused by other signals in
the model.
Languages C, C++
See Also ssSetInputPortReusable
10-62
ssGetInputPortSampleTime
10ssGetInputPortSampleTime
Purpose Get the sample time of an input port.
Syntax ssGetInputPortSampleTime(SimStruct *S, inputPortIdx)
Arguments S
SimStruct representing an S-Function block.
inputPortIdx
Index of port whose sample time is required.
Description Use in any routine (except mdlInitializeSizes) to determine the sample time
of an input port. You should use this macro only if you have specified the
sample times as port-based.
Languages C
See Also ssSetInputPortSampleTime, ssGetInputPortOffsetTime
10-63
ssGetInputPortSampleTimeIndex
10ssGetInputPortSampleTimeIndex
Purpose Get the sample time index of an input port.
Syntax int_T ssGetInputPortSampleTimeIndex(SimStruct *S,
int_T inputPortIdx)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
inputPortIdx
Index of the input port whose sample time index is being set.
Description Returns the index of the sample time for the port.
Languages C, C++
See Also ssSetInputPortSampleTimeIndex
10-64
ssGetInputPortSignal
10ssGetInputPortSignal
Purpose Get the address of a contiguous signal entering an input port.
Syntax const void* ssGetInputPortSignal(SimStruct *S, inputPortIdx)
Arguments S
SimStruct representing an S-Function block.
inputPortIdx
Index of port whose sample time is required.
Description Returns the address of the specified input port. A method should use this macro
only if mdlInitializeSizes has specified that the elements of the input signal
be contiguous, using ssSetInputPortRequiredContiguous.
Languages C, C++
Example The following code demonstrates the use of ssGetInputPortSignal.
nInputPorts = ssGetNumInputPorts(S);
for (i = 0; i < nInputPorts; i++) {
int_T nu = ssGetInputPortWidth(S,i);
if ( ssGetInputPortRequiredContiguous(S,i) ) {
const void *u = ssGetInputPortSignal(S,i);
UseInputVectorInSomeFunction(u, nu);
} else {
InputPtrsType u = ssGetInputPortSignalPtrs(S,i);
for (j = 0; j < nu; j++) {
UseInputInSomeFunction(*u[j]);
}
}
}
If you know that the inputs are always real_T signals, the
ssGetInputPortSignal line in the above code snippet would be
const real_T *u = ssGetInputPortRealSignal(S,i);
See Also ssSetInputPortRequiredContiguous, ssGetInputPortRealSignal
10-65
ssGetInputPortSignalAddress
10ssGetInputPortSignalAddress
Purpose Get the address of an input port’s signal.
Syntax function ssGetInputPortSignalAddress(S : in SimStruct;
port : in Integer := 0) return System.Address;
Arguments S
SimStruct representing an S-Function block.
port
Index of an input port.
Description Returns the address of the signal connected to port.
Languages Ada
Example The following code gets the signal connected to a block’s input port.
uWidth : Integer := ssGetInputPortWidth(S,0);
U : array(0 .. uWidth-1) of Real_T;
for U'Address use ssGetInputPortSignalAddress(S,0);
See Also ssGetInputPortWidth
10-66
ssGetInputPortSignalPtrs
10ssGetInputPortSignalPtrs
Purpose Get pointers to an input port’s signal elements.
Syntax InputPtrsType ssGetInputPortSignalPtrs(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an input port.
Description Returns a pointer to an array of signal element pointers for the specified input
port. For example, if the input port width is 5, this function returns a pointer
to a 5-element pointer array. Each element in the pointer array points to the
specific element of the input signal.
You must use ssGetInputPortRealSignalPtrs to get pointers to signals of
type double (real_T).
Languages C
Example Assume that the input port data types are int8_T.
int_T nInputPorts = ssGetNumInputPorts(S);
for (i = 0; i < nInputPorts; i++) {
InputPtrsType u = ssGetInputPortSignalPtrs(S,i);
InputInt8PtrsType uInt8 = (InputInt8PtrsType)u;
int_T nu = ssGetInputPortWidth(S,i);
for (j = 0; j < nu; j++) {
/* u[j] is an int8_T pointer that points to the j-th element
of the input signal.
*/
UseInputInSomeFunction(*u[j]);
}
See Also ssGetInputPortRealSignalPtrs
10-67
ssGetInputPortWidth
10ssGetInputPortWidth
Purpose Get the width of an input port.
C Syntax int_T ssGetInputPortWidth(SimStruct *S, int_T port)
Ada Syntax function ssGetInputPortWidth(S : in SimStruct;
port : in Integer := 0) return Integer;
Arguments S
SimStruct representing an S-Function block.
port
Index of port whose width is required.
Description Gets the input port number of elements. If the input port is a 1-D array with w
elements, this function returns w. If the input port is an M-by-N matrix, this
function returns m*n. If m or n is unknown, this function returns
DYNAMICALLY_SIZED. Use in any routine (except mdlInitializeSizes) to
determine the width of an input port.
Languages Ada, C
See Also ssSetInputPortWidth
10-68
ssGetIWork
10ssGetIWork
Purpose Get a block’s integer work vector.
Syntax int_T* ssGetIWork(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the integer work vector used by the block represented by S. The vector
consists of elements of type int_T and is of length ssGetNumIWork(S).
Typically, this vector is initialized in mdlStart or mdlInitializeConditions,
updated in mdlUpdate, and used in mdlOutputs. You can use this macro in the
simulation loop, mdlInitializeConditions, or mdlStart routines.
Languages C
See Also ssGetNumIWork, ssSetIWorkValue, ssGetIWorkValue
10-69
ssGetIWorkValue
10ssGetIWorkValue
Purpose Get an element of a block’s integer work vector.
Syntax int_T ssGetIWorkValue(SimStruct *S, int_T idx)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the element returned by this function
Description Returns the idx element of the the integer vector used by the block represented
by S. The vector consists of elements of type int_T and is of length
ssGetNumIWork(S). Typically, this vector is initialized in mdlStart or
mdlInitializeConditions, updated in mdlUpdate, and used in mdlOutputs.
You can use this macro in the simulation loop, mdlInitializeConditions, or
mdlStart routines.
Example The following statement
int_T v = ssGetIWorkValue(s, 0);
is equivalent to
int_T* wv = ssGetIWork(s);
int_T v = wv[0];
Languages C
See Also ssGetNumIWork, ssGetIWork, ssSetIWorkValue
10-70
ssGetModelName
10ssGetModelName
Purpose Get the model name.
Syntax ssGetModelName(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description If S is a SimStruct for an S-Function block, this macro returns the name of the
S-function MEX-file associated with the block. If S is the root SimStruct, this
macro returns the name of the Simulink block diagram.
Languages C
See Also ssGetPath
10-71
ssGetModeVector
10ssGetModeVector
Purpose Get the mode vector.
Syntax int_T *ssGetModeVector(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns a pointer (int_T *) to the mode vector.
This vector has length ssGetNumModes(S). Typically, this vector is initialized in
mdlInitializeConditions if the default value of 0 isn’t acceptable. It is then
used in mdlOutputs in conjunction with nonsampled zero crossings to
determine when the output function should change mode. For example,
consider an absolute value function. When the input is negative, negate it to
create a positive value; otherwise, take no action. This function has two modes.
The output function should be designed not to change modes during minor time
steps. You can also use the mode vector in the mdlZeroCrossings routine to
determine the current mode.
Languages C, C++
See Also ssSetNumModes
10-72
ssGetModeVectorValue
10ssGetModeVectorValue
Purpose Get an element of a block’s mode vector.
Syntax int_T ssGetModeVectorValue(SimStruct *S, element)
Arguments S
SimStruct representing an S-Function block.
elementx
Index of a mode vector element.
Description Returns the specified mode vector element.
Languages C, C++
See Also ssSetModeVectorValue, ssGetModeVector
10-73
ssGetNonsampledZCs
10ssGetNonsampledZCs
Purpose Get the zero-crossing signal values.
Syntax ssGetNonsampledZCs(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns a pointer to the vector containing the current values of the signals that
the variable-step solver monitors for zero crossings. The variable-step solver
tracks the signs of these signals to bracket points where they cross zero. The
solver then takes simulation time steps at the points where the zero crossings
occur. This vector has length ssGetNumNonsampledZCs(S).
Example The following excerpt from matlabroot/simulink/src/sfun_zc.c illustrates
usage of this macro to update the zero-crossing array in the mdlZeroCrossings
callback function.
static void mdlZeroCrossings(SimStruct *S)
{
int_T i;
real_T *zcSignals = ssGetNonsampledZCs(S);
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
int_T nZCSignals = ssGetNumNonsampledZCs(S);
for (i = 0; i < nZCSignals; i++) {
zcSignals[i] = *uPtrs[i];
}
}
Languages C
See Also ssGetNumNonsampledZCs
10-74
ssGetNumContStates
10ssGetNumContStates
Purpose Get the number of continuous states that a block has.
C Syntax int_T ssGetNumContStates(SimStruct *S)
Ada Syntax function ssGetNumContStates(S : in SimStruct) return Integer;
Arguments S
SimStruct representing an S-Function block or model.
Description Returns the number of continuous states in the block or model represented by
S. You can use this macro in any routine except mdlInitializeSizes.
Languages Ada, C
See Also ssSetNumContStates, ssGetNumDiscStates, ssGetContStates
10-75
ssGetNumDataTypes
10ssGetNumDataTypes
Purpose Get number of data types registered for this simulation, including built-in
types.
Syntax int_T ssGetNumDataTypes(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the number of data types registered for this simulation. This includes
all custom data types registered by custom S-Function blocks and all built-in
data types.
Note S-functions register their data types in their implementations of the
mdlInitializeSizes callback function. Therefore, to ensure that this macro
returns an accurate count, your S-function should invoke it only after the
point in the simulation at which Simulink invokes the mdlInitializeSizes
callback function.
Languages C
See Also ssRegisterDataType
10-76
ssGetNumDiscStates
10ssGetNumDiscStates
Purpose Get the number of discrete states that a block has.
Syntax int_T ssGetNumDiscStates(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Use in any routine (except mdlInitializeSizes) to determine the number of
discrete states that the S-function has.
Languages C
See Also ssSetNumDiscStates, ssGetNumContStates
10-77
ssGetNumDWork
10ssGetNumDWork
Purpose Get the number of data type work vectors used by a block.
Syntax int_T ssGetNumDWork(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the number of data type work vectors used by S.
Languages C, C++
See Also ssSetNumDWork
10-78
ssGetNumInputPorts
10ssGetNumInputPorts
Purpose Get the number of input ports that a block has.
C Syntax int_T ssGetNumInputPorts(SimStruct *S)
Ada Syntax function ssGetNumInputPorts(S : in SimStruct) return Integer;
Arguments S
SimStruct representing an S-Function block.
Description Use in any routine (except mdlInitializeSizes) to determine how many input
ports a block has.
Languages Ada, C
See Also ssGetNumOutputPorts
10-79
ssGetNumIWork
10ssGetNumIWork
Purpose Get the size of a block’s integer work vector.
Syntax int_T ssGetNumIWork(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the size of the integer (int_T) work vector used by the block
represented by S. You can use this macro in any routine except
mdlInitializeSizes.
Languages C
See Also ssSetNumIWork, ssGetNumRWork
10-80
ssGetNumModes
10ssGetNumModes
Purpose Get the size of the mode vector.
Syntax ssGetNumModes(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the size of the modes vector. You can use this macro in any routine
except mdlInitializeSizes.
Languages C
See Also ssSetNumNonsampledZCs, ssGetNonsampledZCs
10-81
ssGetNumNonsampledZCs
10ssGetNumNonsampledZCs
Purpose Get the size of the zero-crossing vector.
Syntax ssGetNumNonsampledZCs(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the size of the zero-crossing vector. You can use this macro in any
routine except mdlInitializeSizes.
Languages C
See Also ssSetNumNonsampledZCs, ssGetNonsampledZCs
10-82
ssGetNumOutputPorts
10ssGetNumOutputPorts
Purpose Get the number of output ports that a block has.
C Syntax int_T ssGetNumOutputPorts(SimStruct *S)
Ada Syntax function ssGetNumOutputPorts(S : in SimStruct) return Integer;
Arguments S
SimStruct representing an S-Function block.
Description Use in any routine (except mdlInitializeSizes) to determine how many
output ports a block has.
Languages Ada, C
See Also ssGetNumInputPorts
10-83
ssGetNumParameters
10ssGetNumParameters
Purpose Get the number of parameters that this block has.
Syntax function ssGetNumParameters(S : in SimStruct) return Integer;
Arguments S
SimStruct representing an S-Function block.
Description Returns the number of parameters that this block has.
Languages Ada
10-84
ssGetNumRunTimeParams
10ssGetNumRunTimeParams
Purpose Get the number of run-time parameters created by this S-function.
Syntax int_T ssGetNumRunTimeParams(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Use this function to get the number of run-time parameters created by this
S-function.
Languages C
See Also ssSetNumRunTimeParams
10-85
ssGetNumPWork
10ssGetNumPWork
Purpose Get the size of a block’s pointer work vector.
Syntax int_T ssGetNumPWork(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the size of the pointer work vector used by the block represented by S.
You can use this macro in any routine except mdlInitializeSizes.
Languages C
See Also ssSetNumPWork
10-86
ssGetNumRWork
10ssGetNumRWork
Purpose Get the size of a block’s floating-point work vector.
Syntax int_T ssGetNumRWork(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the size of the floating-point (real_T) work vector used by the block
represented by S. You can use this macro in any routine except
mdlInitializeSizes.
Languages C
See Also ssSetNumRWork
10-87
ssGetNumSampleTimes
10ssGetNumSampleTimes
Purpose Get the number of sample times that a block has.
Syntax int_T ssGetNumSampleTimes(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Use in any routine (except mdlInitializeSizes) to determine the number of
sample times S has.
Languages C
See Also ssSetNumSampleTimes
10-88
ssGetNumSFcnParams
10ssGetNumSFcnParams
Purpose Get the number of parameters that an S-Function block expects.
Syntax int_T ssGetNumSFcnParams(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the number of parameters that S expects the user to enter.
Languages C
See Also ssSetNumSFcnParams
10-89
ssGetOutputPortBeingMerged
10ssGetOutputPortBeingMerged
Purpose Determine whether the output of this block is connected to a Merge block.
Syntax int_T ssGetOutputPortBeingMerged(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of the output port.
Description Returns true if this output port signal is being merged with other signals (this
happens if the S-Function block’s output port is connected to a Merge block
directly or via connection type blocks). This macro returns the correct answer
in and after the S-function's mdlSetWorkWidths method.
Languages C, C++
See Also mdlSetWorkWidths
10-90
ssGetOutputPortComplexSignal
10ssGetOutputPortComplexSignal
Purpose Get the numeric type (complex or real) of an output port.
Syntax CSignal_T ssGetOutputPortComplexSignal(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
Description Returns the numeric type of port: COMPLEX_NO (real signal), COMPLEX_YES
(complex signal) or COMPLEX_INHERITED (dynamically determined).
Languages C
See Also ssSetOutputPortComplexSignal
10-91
ssGetOutputPortDataType
10ssGetOutputPortDataType
Purpose Get the data type of an output port.
C Syntax DTypeId ssGetOutputPortDataType(SimStruct *S, int_T port)
Ada Syntax function ssGetOutputPortDataType (S : in SimStruct;
port : in Integer := 0) return Integer;
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of an output port.
Description Returns the data type of the output port specified by port.
Languages Ada, C
See Also ssSetOutputPortDataType
10-92
ssGetOutputPortDimensions
10ssGetOutputPortDimensions
Purpose Get the dimensions of the signal leaving an output port.
Syntax int_T *ssGetOutputPortDimensions(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
Description Returns an array of integers that specifies the dimensions of the signal leaving
port, e.g., [4 2] for a 4-by-2 matrix array. The size of the dimensions array is
equal to the number of signal dimensions accepted by the port, e.g., 1 for a
vector signal or 2 for a matrix signal.
Languages C
See Also ssGetOutputPortNumDimensions
10-93
ssGetOutputPortFrameData
10ssGetOutputPortFrameData
Purpose Determine whether a port outputs signal frames.
Syntax int_T ssGetOutputPortFrameData(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
Description Returns one of the following:
-1
Port outputs either frame or unframed data.
0
Port outputs unframed data only.
1
Port outputs frame data only.
Languages C
See Also ssSetOutputPortFrameData
10-94
ssGetOutputPortNumDimensions
10ssGetOutputPortNumDimensions
Purpose Get the number of dimensions of an output port.
Syntax int_T ssGetOutputPortNumDimensions(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
Description Returns the number of dimensions of port.
Languages C
10-95
ssGetOutputPortOffsetTime
10ssGetOutputPortOffsetTime
Purpose Get the offset time of an output port.
Syntax real_T ssGetOutputPortOffsetTime(SimStruct *S,outputPortIdx)
Arguments S
SimStruct representing an S-Function block.
outputPortIdx
Index of an output port.
Description Use in any routine (except mdlInitializeSizes) to determine the sample time
of an output port. This macro should only be used if you have specified
port-based sample times.
Languages C
See Also ssSetOutputPortOffsetTime, ssGetOutputPortSampleTime
10-96
ssGetOutputPortRealSignal
10ssGetOutputPortRealSignal
Purpose Get a pointer to an output signal of type double (real_T).
Syntax real_T *ssGetOutputPortRealSignal(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
Description Use in any simulation loop routine, mdlInitializeConditions, or mdlStart to
access an output port signal where the output port index starts at 0 and must
be less than the number of output ports. This returns a contiguous real_T
vector of length equal to the width of the output port.
Example To write to all output ports, you would use
int_T i,j;
int_T nOutputPorts = ssGetNumOutputPorts(S);
for (i = 0; i < nOutputPorts; i++) {
real_T *y = ssGetOutputPortRealSignal(S,i);
int_T ny = ssGetOutputPortWidth(S,i);
for (j = 0; j < ny; j++) {
y[j] = SomeFunctionToFillInOutput();
}
}
Languages C
See Also ssGetInputPortRealSignalPtrs
10-97
ssGetOutputPortReusable
10ssGetOutputPortReusable
Purpose Determine whether memory allocated to the output port is reusable.
Syntax int_T ssGetOutputPortReusable(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of an output port.
Description Returns true if the output port memory buffer can be reused by other signals
in the model.
Languages C, C++
See Also ssSetOutputPortReusable
10-98
ssGetOutputPortSampleTime
10ssGetOutputPortSampleTime
Purpose Get the sample time of an output port.
Syntax ssGetOutputPortSampleTime(SimStruct *S,outputPortIdx)
Arguments S
SimStruct representing an S-Function block.
outputPortIdx
Index of an output port.
Description Use in any routine (except mdlInitializeSizes) to determine the sample time
of an output port. This macro should only be used if you have specified
port-based sample times.
Languages C
See Also ssSetOutputPortSampleTime
10-99
ssGetOutputPortSignal
10ssGetOutputPortSignal
Purpose Get the vector of signal elements emitted by an output port.
Syntax void *ssGetOutputPortSignal(SimStruct *S, int_T port)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
Description Returns a pointer to the vector of signal elements output by port.
Note If the port outputs a signal of type double (real_T), you must use
ssGetOutputPortRealSignal to get the signal vector.
Example Assume that the output port data types are int16_T.
nOutputPorts = ssGetNumOutputPorts(S);
for (i = 0; i < nOutputPorts; i++) {
int16_T *y = (int16_T *)ssGetOutputPortSignal(S,i);
int_T ny = ssGetOutputPortWidth(S,i);
for (j = 0; j < ny; j++) {
SomeFunctionToFillInOutput(y[j]);
}
}
Languages C
See Also ssGetOutputPortRealSignal
10-100
ssGetOutputPortSignalAddress
10ssGetOutputPortSignalAddress
Purpose Get address of an output port’s signal.
Syntax ssGetOutputPortSignalAddress(S : in SimStruct; port : in Integer :=
0) return System.Address
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
Description Returns the address of the signal connected to port.
Languages Ada
Example The following code gets the signal connected to a block’s input port.
yWidth : Integer := ssGetOutputPortWidth(S,0);
Y : array(0 .. yWidth-1) of Real_T;
for Y'Address use ssGetOutputPortSignalAddress(S,0);
See Also ssGetOutputPortWidth
10-101
ssGetOutputPortWidth
10ssGetOutputPortWidth
Purpose Get the width of an output port.
C Syntax int_T ssGetOutputPortWidth(SimStruct *S, int_T port)
Ada Syntax function ssGetOutputPortWidth(S : in SimStruct; port : in Integer
:= 0) return Integer;
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
Description Use in any routine (except mdlInitializeSizes) to determine the width of an
output port where the output port index starts at 0 and must be less than the
number of output ports.
Languages Ada, C
See Also ssSetOutputPortWidth
10-102
ssGetParentSS
10ssGetParentSS
Purpose Get the parent of a SimStruct.
Syntax SimStruct *ssGetParentSS(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description Returns the parent SimStruct of S, or NULL if S is the root SimStruct.
Note There is one SimStruct for each S-function in your model and one for
the model itself. The structures are arranged as a tree with the model
SimStruct as the root. User-written S-functions should not use the
ssGetParentSS macro.
Languages C
See Also ssGetRootSS
10-103
ssGetPath
10ssGetPath
Purpose Get the path of a block.
C Syntax const char_T *ssGetPath(SimStruct *S)
Ada Syntax function ssGetPath(S : in SimStruct) return String;
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description If S is an S-Function block, this macro returns the full Simulink path to the
block. If S is the root SimStruct of the model, this macro returns the model
name. In a C MEX S-function, in mdlInitializeSizes, if
strcmp(ssGetModelName(S),ssGetPath(S))==0
the S-function is being called from MATLAB and is not part of a simulation.
Languages Ada, C
See Also ssGetModelName
10-104
ssGetPlacementGroup
10ssGetPlacementGroup
Purpose Get the name of the placement group of a block.
Syntax const char *ssGetPlacementGroup(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model. The block
must be either a source block (i.e., a block without input ports) or a sink block
(i.e., a block without output ports).
Description Use this macro in mdlInitializeSizes to get the name of this block’s
placement group.
Note This macro is typically used to create Real-Time Workshop device
driver blocks.
Languages C
See Also ssSetPlacementGroup
10-105
ssGetPortBasedSampleTimeBlockIsTriggered
10ssGetPortBasedSampleTimeBlockIsTriggered
Purpose Determine whether a block that uses port-based sample times resides in a
triggered subsystem.
Syntax boolean_T ssGetPortBasedSampleTimeBlockIsTriggered(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns TRUE if S uses port-based sample times and resides in a triggered
subsystem. Use this macro in mdlOutputs and mdlUpdate to decode whether to
use the block’s triggered or non-triggered algorithms to compute its states and
outputs.
Note This macro returns a valid result only after sample time propagation.
Thus, you cannot use it in mdlSetInputPortSampleTime and
mdlSetOutputPortSampleTime to determine whether a port’s sample time is
triggered. Use ssSampleAndOffsetAreTriggered instead.
Languages C
10-106
ssGetPWork
10ssGetPWork
Purpose Get a block’s pointer work vector.
Syntax void** ssGetPWork(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the pointer work vector used by the block represented by S. The vector
consists of elements of type void * and is of length ssGetNumPWork(S).
Typically, this vector is initialized in mdlStart or mdlInitializeConditions,
updated in mdlUpdate, and used in mdlOutputs. You can use this macro in the
simulation loop, mdlInitializeConditions, or mdlStart routines.
Languages C
See Also ssGetNumPWork
10-107
ssGetPWorkValue
10ssGetPWorkValue
Purpose Get a pointer from a block’s pointer work vector.
Syntax void* ssGetPWorkValue(SimStruct *S, int_T idx)
Arguments S
SimStruct representing an S-function block.
idx
Index of the pointer returned by this function
Description Returns the idx element of the the pointer work vector used by the block
represented by S. The vector consists of elements of type void * and is of length
ssGetNumPWork(S). Typically, this vector is initialized in mdlStart or
mdlInitializeConditions, updated in mdlUpdate, and used in mdlOutputs.
You can use this macro in the simulation loop, mdlInitializeConditions, or
mdlStart routines.
Example The following statement
void* v = ssGetPWorkValue(s, 0);
is equivalent to
void** wv = ssGetPWork(s);
void* v = wv[0];
Languages C
See Also ssGetNumPWork, ssGetPWork, ssSetPWorkValue
10-108
ssGetRealDiscStates
10ssGetRealDiscStates
Purpose Get a block’s discrete state vector.
Syntax real_T *ssGetRealDiscStates(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Same as ssGetDiscStates.
Languages C
See Also ssGetDiscStates
10-109
ssGetRootSS
10ssGetRootSS
Purpose Get the root of a SimStruct hierarchy.
Syntax SimStruct *ssGetRootSS(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description Returns the root of the SimStruct hierarchy containing S.
Languages C
See Also ssGetParentSS
10-110
ssGetRunTimeParamInfo
10ssGetRunTimeParamInfo
Purpose Gets the attributes of a run-time parameter.
Syntax ssParamRec *ssGetRunTimeParamInfo(SimStruct *S, int_T param)
Arguments S
SimStruct representing an S-Function block.
param
Index of a run-time parameter.
Description Returns the attributes of the run-time parameter specified by param. See the
documentation for ssSetRunTimeParamInfo for a description of the ssParamRec
structure returned by this function.
Languages C
See Also ssSetRunTimeParamInfo
10-111
ssGetRWork
10ssGetRWork
Purpose Get a block’s floating-point work vector.
Syntax real_T* ssGetRWork(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the floating-point work vector used by the block represented by S. The
vector consists of elements of type real_T and is of length ssGetNumRWork(S).
Typically, this vector is initialized in mdlStart or mdlInitializeConditions,
updated in mdlUpdate, and used in mdlOutputs. You can use this macro in the
simulation loop, mdlInitializeConditions, or mdlStart routines.
Languages C
See Also ssGetNumRWork, ssGetRWorkValue, ssSetRWorkValue
10-112
ssGetRWorkValue
10ssGetRWorkValue
Purpose Get an element of a block’s floating-point work vector.
Syntax real_T ssGetRWorkValue(SimStruct *S, int_T idx)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the element returned by this function
Description Returns the idx element of the the floating-point work vector used by the block
represented by S. The vector consists of elements of type real_T and is of length
ssGetNumRWork(S). Typically, this vector is initialized in mdlStart or
mdlInitializeConditions, updated in mdlUpdate, and used in mdlOutputs.
You can use this macro or ssGetRWork to get the current values of the work
vector in the simulation loop, mdlInitializeConditions, or mdlStart
routines.
Example The following statement
real_T v = ssGetRWorkValue(s, 0);
is equivalent to
real_T* wv = ssGetRWork(s);
real_T v = wv[0];
Languages C
See Also ssGetNumRWork, ssGetRWork, ssSetRWorkValue
10-113
ssGetSampleTimeOffset
10ssGetSampleTimeOffset
Purpose Get the offset of the current sample time.
Syntax function ssGetSampleTimeOffset(S : in SimStruct) return time_T;
Arguments S
SimStruct representing an S-Function block.
Description Returns the offset of the current sample time.
Languages Ada
See Also ssGetSampleTimePeriod
10-114
ssGetSampleTimePeriod
10ssGetSampleTimePeriod
Purpose Get the period of the current sample time.
Syntax function ssGetSampleTimePeriod(S : in SimStruct) return time_T;
Arguments S
SimStruct representing an S-Function block.
Description Returns the period of the current sample time.
Languages Ada
See Also ssGetSampleTimeOffset
10-115
ssGetSFcnParam
10ssGetSFcnParam
Purpose Get a parameter of an S-Function block.
Syntax const mxArray *ssGetSFcnParam(SimStruct *S, int_T index)
Arguments S
SimStruct representing an S-Function block.
index
Index of the parameter to be returned.
Description Use in any routine to access a parameter entered in the S-Function’s block
dialog box, where index starts at 0 and is less than ssGetSFcnParamsCount(S).
Languages C
See Also ssGetSFcnParamsCount
10-116
ssGetSFcnParamsCount
10ssGetSFcnParamsCount
Purpose Get the number of block dialog parameters that an S-Function block has.
Syntax int_T ssGetSFcnParamsCount(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the number of parameters that a user can set for the block represented
by S.
Languages C
See Also ssGetNumSFcnParams
10-117
ssGetSimMode
10ssGetSimMode
Purpose Get the simulation mode an S-Function block.
Syntax ssGetSimMode(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description Returns the simulation mode of the block represented by S:
SS_SIMMODE_NORMAL
Running in a normal Simulink simulation
SS_SIMMODE_SIZES_CALL_ONLY
Invoked by editor to obtain number of ports
SS_SIMMODE_RTWGEN
Generating code
SS_SIMMODE_EXTERNAL
External mode simulation
Languages C
See Also ssGetSolverName
10-118
ssGetSolverMode
10ssGetSolverMode
Purpose Get the solver mode being used to solve the S-function.
Syntax SolverMode ssGetSolverMode(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description Returns one of
SOLVER_MODE_AUTO
SOLVER_MODE_SINGLETASKING
SOLVER_MODE_MULTITASKING
This macro can return SOLVER_MODE_AUTO in mdlInitializeSizes. However,
in mdlSetWorkWidths and any methods called after mdlSetWorkWidths, solver
mode is either SOLVER_MODE_SINGLETASKING or SOLVER_MODE_MULTITASKING.
Languages C, C++
See Also ssGetSimMode, ssIsVariableStepSolver
10-119
ssGetSolverName
10ssGetSolverName
Purpose Get the name of the solver being used to solve the S-function.
Syntax ssGetSolverName(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description Returns a pointer (char *) to the name of the solver being used to solve the
S-function represented by S.
Languages C
See Also ssGetSimMode, ssIsVariableStepSolver
10-120
ssGetStateAbsTol
10ssGetStateAbsTol
Purpose Get the absolute tolerance used by the model’s variable-step solver for a
specified state.
Syntax real_T ssGetStateAbsTol(SimStruct *S, int_T state)
Arguments S
SimStruct representing an S-Function block.
Description Use in mdlStart to get the absolute tolerance for a particular state.
Note Absolute tolerances are not allocated for fixed-step solvers. Therefore,
you should not invoke this macro until you have verified that the simulation is
using a variable-step solver, using ssIsVariableStepSolver.
Languages C, C++
See Also ssGetAbsTol, ssIsVariableStepSolver
10-121
ssGetStopRequested
10ssGetStopRequested
Purpose Get the value of the simulation stop requested flag.
Syntax int_T ssGetStopRequested(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description Gets the value of the simulation stop requested flag. If the value is not 0,
Simulink halts the simulation at the end of the current time step.
Languages C
See Also ssSetStopRequested
10-122
ssGetT
10ssGetT
Purpose Get the current simulation time.
C Syntax ssGetT(SimStruct *S)
Ada Syntax function ssGetT(S : in SimStruct) return Real_T;
Arguments S
SimStruct representing an S-Function block.
Description Returns the current base simulation time (time_T) for the model. You can use
this macro in mdlOutputs and mdlUpdate to compute the output of your block.
Note Use this macro only if your block operates at the base rate of the model,
for example, if your block operates at a single continuous rate. If your block
operates at multiple rates or operates at a single rate that is different from
the model’s base, use ssGetTaskTime to get the correct time for the current
task.
Languages Ada, C
See Also ssGetTaskTime, ssGetTStart, ssGetTFinal
10-123
ssGetTaskTime
10ssGetTaskTime
Purpose Get the current time for the current task.
Syntax ssGetTaskTime(SimStruct *S, st_index)
Arguments S
SimStruct representing an S-Function block.
st_index
Index of the sample time corresponding to the task for which the current time
is to be returned.
Description Returns the current time (time_T) of the task corresponding to the sample rate
specified by st_index. You can use this macro in mdlOutputs and mdlUpdate to
compute the output of your block.
Languages C
See Also ssGetT
10-124
ssGetTFinal
10ssGetTFinal
Purpose Get the simulation stop time.
C Syntax time_T ssGetTFinal(SimStruct *S)
Ada Syntax function ssGetTFinal(S : in SimStruct) return Real_T;
Arguments S
SimStruct representing an S-Function block.
Description Returns the stop time of the current simulation.
Languages Ada, C
See Also ssGetT, ssGetTStart
10-125
ssGetTNext
10ssGetTNext
Purpose Get the time of the next sample hit.
Syntax time_T ssGetTNext(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns the next time that a sample hit occurs in a discrete S-function with a
variable sample time.
Languages C
See Also ssSetTNext, mdlGetTimeOfNextVarHit
10-126
ssGetTStart
10ssGetTStart
Purpose Get the simulation start time.
C Syntax time_T ssGetTStart(SimStruct *S)
Ada Syntax function ssGetTStart(S : in SimStruct) return Real_T;
Arguments S
SimStruct representing an S-Function block.
Description Returns the start time of the current simulation.
Languages Ada, C
See Also ssGetT, ssGetTFinal
10-127
ssGetUserData
10ssGetUserData
Purpose Access user data.
Syntax void ssGetUserData(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Retrieves a pointer to user data.
Languages C, C++
See Also ssSetUserData
10-128
ssIsContinuousTask
10ssIsContinuousTask
Purpose Determine whether a task is continuous.
Syntax ssIsContinuousTask(SimStruct *S,st_index,tid)
Arguments S
SimStruct representing an S-Function block.
tid
Task ID.
Description Use in mdlOutputs or mdlUpdate when your S-function has multiple sample
times to determine whether your S-function is executing in the continuous
task. You should not use this in single-rate S-functions, or if you did not
register a continuous sample time.
Languages C
See Also ssSetNumContStates
10-129
ssIsFirstInitCond
10ssIsFirstInitCond
Purpose Determine whether this is the first call to mdlInitializeConditions.
Syntax int_T ssIsFirstInitCond(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns true if the current simulation time is equal to the simulation start
time.
Languages C
See Also mdlInitializeConditions
10-130
ssIsMajorTimeStep
10ssIsMajorTimeStep
Purpose Determine whether the simulation is in a major step.
C Syntax int_T ssIsMajorTimeStep(SimStruct *S)
Ada Syntax function ssIsMajorTimeStep(S : in SimStruct) return Boolean;
Arguments S
SimStruct representing an S-Function block.
Description Returns 1 if the simulation is in a major time step.
Languages Ada, C
See Also ssIsMinorTimeStep
10-131
ssIsMinorTimeStep
10ssIsMinorTimeStep
Purpose Determine whether the simulation is in a minor step.
Syntax int_T ssIsMinorTimeStep(SimStruct *S)
Arguments S
SimStruct representing an S-Function block.
Description Returns 1 if the simulation is in a minor time step.
Languages C
See Also ssIsMajorTimeStep
10-132
ssIsSampleHit
10ssIsSampleHit
Purpose Determine whether the sample time is hit.
Syntax ssIsSampleHit(SimStruct *S,st_index,tid)
Arguments S
SimStruct representing an S-Function block.
st_index
Index of the sample time.
tid
Task ID.
Description Use in mdlOutputs or mdlUpdate when your S-function has multiple sample
times to determine the task your S-function is executing in. You should not use
this in single-rate S-functions or for an st_index corresponding to a continuous
task.
Languages C
See Also ssIsContinuousTask, ssIsSpecialSampleHit
10-133
ssIsSpecialSampleHit
10ssIsSpecialSampleHit
Purpose Determine whether sample is hit.
Syntax ssIsSpecialSampleHit(SimStruct *S, sti1, sti2, tid)
Arguments S
SimStruct representing an S-Function block.
sti1
Index of the sample time.
sti2
Index of the sample time.
tid
Task ID.
Description Returns true if a sample hit has occurred at sti1 and a sample hit has also
occurred at sti2 in the same time step. You can use this macro in mdlUpdate
and mdlOutputs to ensure the validity of data shared by multiple tasks running
at different rates. For more information, see “Synchronizing Multirate
S-Function Blocks” on page 7-24.
Languages C
See Also ssIsSampleHit
10-134
ssIsVariableStepSolver
10ssIsVariableStepSolver
Purpose Get the name of the solver being used to solve the S-function.
Syntax ssIsVariableStepSolver(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description Returns 1 if the solver being used to solve S is a variable-step solver. This is
useful when you are creating S-functions that have zero crossings and an
inherited sample time.
Languages C
See Also ssGetSimMode, ssGetSolverName
10-135
ssPrintf
10ssPrintf
Purpose Print a variable-content message.
Syntax ssPrintf(msg, ...)
Arguments msg
Message. Must be a string with optional variable replacement parameters.
...
Optional replacement arguments.
Description Prints variable-content msg. This macro expands to mexPrintf when the
S-function is compiled via mex for use with Simulink. When the S-function is
compiled for use with the Real-Time Workshop, this macro expands to printf
if the target has stdio facilities; otherwise, it becomes a call to an empty
function (rtPrintfNoOp). In the case of Real-Time Workshop, you can avoid a
call altogether, using the SS_STDIO_AVAILABLE macro. For example:
#if defined(SS_STDIO_AVAILABLE)
ssPrintf("my message ...");
#endif
Languages C
See Also ssWarning
10-136
ssRegDlgParamAsRunTimeParam
10ssRegDlgParamAsRunTimeParam
Purpose Register a dialog parameter as a run-time parameter.
Syntax ssRegDlgParamAsRunTimeParam(S, dlgIdx, rtIdx, name, dtId)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
dlgIdx
Index of the dialog parameter
rtIdx
Index of the run-time parameter
name
Name of the parameter
dtId
Value of type DTypeId that specifies the data type of the run-time parameter
Description Use this function in mdlSetWorkWidths to register the dialog parameter
specified by dlgIdx as a run-time parameter specified by rtIdx and having the
name and data type specified by name and dtId, respectively. This function also
initializes the run-time parameter to the initial value of the dialog parameter,
converting the value to the specified data type if necessary.
Note The first four characters of block’s run-time parameter names must be
unique. If they are not, Simulink signals an error. For example, trying to
register a parameter named param2 triggers an error if a parameter named
param1 already exists.
Languages C
See Also ssRegAllTunableParamsAsRunTimeParams
10-137
ssRegAllTunableParamsAsRunTimeParams
10ssRegAllTunableParamsAsRunTimeParams
Purpose Register all tunable parameters as run-time parameters.
Syntax void ssRegAllTunableParamsAsRunTimeParams(S,
const char_T *names[]))
Arguments S
SimStruct representing an S-Function block.
names
Array of names for the run-time parameters.
Note The first four characters of block’s run-time parameter names must be
unique. If they are not, Simulink signals an error. For example, trying to
register a parameter named param2 triggers an error if a parameter named
param1 already exists.
Description Use this function in mdlSetWorkWidths to register all tunable dialog
parameters as run-time parameters. Specify the names of the run-time
versions of the parameters in the names array.
Note Simulink assumes that the names array is always available. Therefore,
you must allocate the names array in such a way that it persists throughout
the simulation.
You can register dialog parameters individually as run-time parameters, using
ssSetNumRunTimeParams and ssSetRunTimeParamInfo.
Languages C
See Also mdlSetWorkWidths, ssSetNumRunTimeParams, ssSetRunTimeParamInfo
10-138
ssRegisterDataType
10ssRegisterDataType
Purpose Register a custom data type.
Syntax DTypeId ssRegisterDataType(SimStruct *S, char *name)
Arguments S
SimStruct representing an S-Function block.
name
Name of custom data type.
Description Register a custom data type. Each data type must be a valid MATLAB
identifier. That is, the first char is an alpha and all subsequent characters are
alphanumeric or "_". The name length must be less than 32. Data types must be
registered in mdlInitializeSizes.
If the registration is successful, the function returns the DataTypeId associated
with the registered data type; otherwise, it reports an error and returns
INVALID_DTYPE_ID.
After registering the data type, you must specify its size, using
ssSetDataTypeSize.
Note You can call this function to get the data type ID associated with a
registered data type.
Example The following example registers a custom data type named Color.
DTypeId id = ssRegisterDataType(S, "Color");
if(id == INVALID_DTYPE_ID) return;
Languages C
See Also ssSetDataTypeSize
10-139
ssSampleAndOffsetAreTriggered
10ssSampleAndOffsetAreTriggered
Purpose Determine whether a sample time and offset value pair indicate a triggered
sample time.
Syntax boolean_T ssSampleAndOffsetAreTriggered(real_T st, real_T ot)
Arguments st
The sample time
ot
The offset time
Description Returns TRUE if both st and ot are equal to INHERITED_SAMPLE_TIME.
Simulink sets the sample time and offset pairs of a block or its ports (for
port-based sample times) to INHERITED_SAMPLE_TIME if the block resides in a
triggered subsystem. By invoking this macro on its sample time/offset pairs, an
S-function can determine whether it resides in a triggered subsystem.
Languages C
10-140
ssSetBlockReduction
10ssSetBlockReduction
Purpose Request that Simulink attempt to reduce a block.
Syntax ssSetBlockReduction(SimStruct *S, unsigned int_T flag)
Arguments S
SimStruct representing an S-Function block.
flag
If true, Simulink should attempt to reduce this block.
Description Use this macro to ask Simulink to reduce this block. A block is reducible if it
can be eliminated from the model without affecting the model’s behavior.
Simulink optimizes performance by skipping execution of reducible blocks
during model simulation. In particular, Simulink does not invoke the
mdlStart, mdlUpdate, and mdlOutputs methods of reducible blocks. Further,
Simulink executes the mdlTerminate method of a reduced block only if the
block has set the SS_OPTION_CALL_TERMINATE_AT_EXIT option before the
simulation loop has begun, using ssSetOptions.
A block must meet certain criteria to be considered reducible. For example, a
block must have at least one input, must have the same number of outputs as
inputs or no outputs, and none of the block’s inputs can be a bus signal. If a
block fails to meet any of these criteria, Simulink includes the block in the
simulation regardless of whether the block has requested reduction.
Your S-function must invoke this macro before Simulink would otherwise
invoke the S-function’s mdlStart method (see the callback flow diagram in
“How Simulink Interacts with C S-Functions” on page 3-35). This means your
S-function must invoke this macro no later than its mdlSetWorkWidths method
to be considered a candidate for block reduction.
Languages C
See Also ssGetBlockReduction
10-141
ssSetCallSystemOutput
10ssSetCallSystemOutput
Purpose Specify that an output port is issuing a function call.
Syntax ssSetCallSystemOutput(SimStruct *S, port_index)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port_index
Index of the port that is issuing the function call.
Description Use in mdlInitializeSampleTimes to specify that the output port element
specified by port_index is issuing a function call by using
ssCallSystemWithTid(S,index,tid). The index specified starts at 0 and
must be less than ssGetOutputPortWidth(S,0).
Languages C
See Also ssCallSystemWithTid
10-142
ssSetDataTypeSize
10ssSetDataTypeSize
Purpose Set the size of a custom data type.
Syntax int_T ssSetDataTypeSize(SimStruct *S, DTypeId id, int_T size)
Arguments S
SimStruct representing an S-Function block.
id
ID of data type.
size
Size of the custom data type in bytes.
Description Sets the size of the data type specified by id to size. If the call is successful,
the macro returns 1 (true), otherwise, it returns 0 (false). Use this macro in
mdlInitializeSizes to set the size of a data type you have registered.
Example The following example registers and sets the size of the custom data type
named Color to 4 bytes.
int_T status;
DTypeId id;
id = ssRegisterDataType(SimStruct *S, "Color");
if(id == INVALID_DTYPE_ID) return;
status = ssSetDataTypeSize(S, id, 4);
if(status == 0) return;
Languages C
See Also ssRegisterDataType, ssGetDataTypeSize
10-143
ssSetDataTypeZero
10ssSetDataTypeZero
Purpose Set zero representation of a data type.
Syntax int_T ssSetDataTypeZero(SimStruct *S, DTypeId id, void* zero)
Arguments S
SimStruct representing an S-Function block.
id
ID of data type.
zero
Zero representation of the data type specified by id.
Description Sets the zero representation of the data type specified by id to 0 and returns 1
(true) if id is valid, the size of the data type has been set, and the zero
representation has not already been set. Otherwise, this macro returns 0 (false)
and reports an error. Because this macro reports any error that occurs, you do
not need to use ssSetErrorStatus to report the error.
Note This macro makes a copy of the zero representation of the data type for
Simulink’s use. Thus, your S-function does not have to maintain the original
in memory.
Languages C
Example The following example registers and sets the size and zero representation of a
custom data type named myDataType.
typedef struct{
int8_T a;
uint16_T b;
}myStruct;
int_T status;
DTypeId id;
myStruct tmp;
id = ssRegisterDataType(S, "myDataType");
10-144
ssSetDataTypeZero
if(id == INVALID_DTYPE_ID) return;
status = ssSetDataTypeSize(S, id, sizeof(tmp));
if(status == 0) return;
tmp.a = 0;
tmp.b = 1;
status = ssSetDataTypeZero(S, id, &tmp);
if(status == 0) return;
See Also ssRegisterDataType, ssSetDataTypeSize, ssGetDataTypeZero
10-145
ssSetDWorkComplexSignal
10ssSetDWorkComplexSignal
Purpose Specify whether the elements of a data type work vector are real or complex.
Syntax void ssSetDWorkComplexSignal(SimStruct *S, int_T vector,
CSignal_T numType)
Arguments S
SimStruct representing an S-Function block.
vector
Index of a data type work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
numType
Numeric type, either COMPLEX_YES or COMPLEX_NO.
Description Use in mdlInitializeSizes or mdlSetWorkWidths to specify whether the
values of the specified work vector are complex numbers (COMPLEX_YES) or real
numbers (COMPLEX_NO, the default).
Languages C, C++
See Also ssSetDWorkDataType, ssGetNumDWork
10-146
ssSetDWorkDataType
10ssSetDWorkDataType
Purpose Specify the data type of a data type work vector.
Syntax void ssSetDWorkDataType(SimStruct *S, int_T vector, DTypeId dtID)
Arguments S
SimStruct representing an S-Function block.
vector
Index of a data type work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
dtID
ID of a data type.
Description Use in mdlInitializeSizes or mdlSetWorkWidths to set the data type of the
specified work vector.
Languages C, C++
See Also ssSetDWorkWidth, ssGetNumDWork
10-147
ssSetDWorkName
10ssSetDWorkName
Purpose Specify the name of a data type work vector.
Syntax void ssSetDWorkName(SimStruct *S, int_T vector, char_T *name)
Arguments S
SimStruct representing an S-Function block.
vector
Index of the work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
name
Name of a work vector.
Description Use in mdlInitializeSizes or in mdlSetWorkWidths to specify a name for the
specified data type work vector. The Real-Time Workshop uses this name to
label the work vector in generated code. If you do not specify a name, the
Real-Time Workshop generates a name for the work vector.
Languages C, C++
See Also ssGetDWorkName, ssSetNumDWork
10-148
ssSetDWorkRTWIdentifier
10ssSetDWorkRTWIdentifier
Purpose Specify the identifier used to declare a DWork vector in code generated from
the associated S-function.
Syntax void ssSetDWorkRTWIdentifier(SimStruct* S, int idx, char_T * id)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
id
Identifier
Description Specifies id as the identifier used in code generated by the Real-Time
Workshop to declare the DWork vector specified by idx.
Languages C, C++
See Also ssSetDWorkRTWIdentifier
10-149
ssSetDWorkRTWStorageClass
10ssSetDWorkRTWStorageClass
Purpose Specify the storage class of a DWork vector in code generated from the
associated S-function.
Syntax void ssSetDWorkRTWStorageClass(SimStruct* S, int idx,
ssRTWStorageType sc)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
sc
Storage class of the work vector. Must be one of the values enumerated by
ssRTWStorageType in simstruc.h:
typedef enum {
SS_RTW_STORAGE_AUTO = 0,
SS_RTW_STORAGE_EXPORTED_GLOBAL,
SS_RTW_STORAGE_IMPORTED_EXTERN,
SS_RTW_STORAGE_IMPORTED_EXTERN_POINTER
} ssRTWStorageType
Description Sets sc as the storage class of the the DWork vector specified by idx. The
storage class is a code-generation attribute that determines how the code
generated by the Real-Time Workshop for this S-function allocates memory for
this work vector (see “Signal Storage Concepts” in the online documentation for
the Real-Time Workshop).
Languages C, C++
See Also ssGetDWorkRTWStorageClass
10-150
ssSetDWorkRTWTypeQualifier
10ssSetDWorkRTWTypeQualifier
Purpose Specify the C type qualifier (e.g., const) used to declare a DWork vector in code
generated from the associated S-function.
Syntax void ssSetDWorkRTWTypeQualifier(SimStruct* S, int idx, char_T * tq)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
tq
type qualifier
Description Sets tq as the C type qualifier (e.g., const) used to declare the DWork vector
specified by idx in code generated by the Real-Time Workshop from the
associated S-function.
Languages C, C++
See Also ssGetDWorkRTWTypeQualifier
10-151
ssSetDWorkUsedAsDState
10ssSetDWorkUsedAsDState
Purpose Specify that a data type work vector is used as a discrete state vector.
Syntax void ssSetDWorkUsedAsDState(SimStruct *S, int_T vector,
int_T usage)
Arguments S
SimStruct representing an S-Function block.
vector
Index of a data type work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
usage
How this vector is used.
Description Use in mdlInitializeSizes or mdlSetWorkWidths to specify the usage of the
specified work vector, either SS_DWORK_USED_AS_DSTATE (used to store the
block’s discrete states) or SS_DWORK_USED_AS_DWORK (used as a work vector, the
default).
Note Specify the usage as SS_DWORK_USED_AS_DSTATE if the following
conditions are true. You want to use the vector to store discrete states and you
want Simulink to log the discrete states to the workspace at the end of a
simulation, if the user has selected the Save to Workspace option on
Simulink’s Simulation Parameters dialog.
Languages C, C++
See Also ssGetDWorkUsedAsDState
10-152
ssSetDWorkWidth
10ssSetDWorkWidth
Purpose Specify the width of a data type work vector.
Syntax void ssSetDWorkWidth(SimStruct *S, int_T vector, int_T width)
Arguments S
SimStruct representing an S-Function block.
vector
Index of the work vector, where the index is one of 0, 1, 2, ...
ssGetNumDWork(S).
width
Number of elements in the work vector.
Description Use in mdlInitializeSizes or in mdlSetWorkWidths to set the number of
elements in the specified data type work vector.
Languages C, C++
See Also ssGetDWorkWidth, ssSetDWorkDataType, ssSetNumDWork
10-153
ssSetErrorStatus
10ssSetErrorStatus
Purpose Report an error.
C Syntax void ssSetErrorStatus(SimStruct *S, const char_T *msg)
Ada Syntax procedure ssSetErrorStatus(S : in SimStruct; msg : in String);
Arguments S
SimStruct representing an S-Function block or a Simulink model.
msg
Error message.
Description Use this function to report errors that occur in your S-function. For example:
ssSetErrorStatus(S, "error message");
return;
Note The error message string must be in persistent memory; it cannot be a
local variable.
Languages Ada, C
See Also ssWarning
10-154
ssSetExternalModeFcn
10ssSetExternalModeFcn
Purpose Specify the external mode function for an S-function.
Syntax void ssSetExternalModeFcn(SimStruct *S, SFunExtModeFcn *fcn)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
fcn
External mode function.
Description Specifies the external mode function for S.
Languages C
See Also ssCallExternalModeFcn
10-155
ssSetInputPortComplexSignal
10ssSetInputPortComplexSignal
Purpose Set the numeric type (real or complex) of an input port.
Syntax void ssSetInputPortComplexSignal(SimStruct *S, input_T port,
CSignal_T csig)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of an input port.
csignal
Numeric type of the signals accepted by port. Valid values are COMPLEX_NO
(real signal), COMPLEX_YES (complex signal), and COMPLEX_INHERITED (numeric
type inherited from driving block).
Description Use this function in mdlInitializeSizes to initialize input port signal type. If
the numeric type of the input port is inherited from the block to which it is
connected, set the numeric type to COMPLEX_INHERITED. The default numeric
type of an input port is real.
Languages C
Example Assume that an S-function has three input ports. The first input port accepts
real (noncomplex) signals. The second input port accepts complex signals. The
third port accepts signals of either type. The following example specifies the
correct numeric type for each port.
ssSetInputPortComplexSignal(S, 0, COMPLEX_NO)
ssSetInputPortComplexSignal(S, 1, COMPLEX_YES)
ssSetInputPortComplexSignal(S, 2, COMPLEX_INHERITED)
See Also ssGetInputPortComplexSignal
10-156
ssSetInputPortDataType
10ssSetInputPortDataType
Purpose Set the data type of an input port.
C Syntax void ssSetInputPortDataType(SimStruct *S,input_T port, DTypeId id)
Ada Syntax procedure ssSetInputPortDataType(S : in SimStruct;
port : in Integer := 0; id : in Integer);
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of an input port.
id
ID of the data type accepted by port.
Description Use this function in mdlInitializeSizes to set the data type of the input port
specified by port. If the input port’s data type is inherited from the block
connected to the port, set the data type to DYNAMICALLY_TYPED.
Note The data type of an input port is double (real_T) by default.
Languages Ada, C
Example Suppose that you want to create an S-function with two input ports, the first of
which inherits its data type from the driving block and the second of which
accepts inputs of type int8_T. The following code sets up the data types.
ssSetInputPortDataType(S, 0, DYNAMICALLY_TYPED)
ssSetInputPortDataType(S, 1, SS_INT8)
See Also ssGetInputPortDataType
10-157
ssSetInputPortDimensionInfo
10ssSetInputPortDimensionInfo
Purpose Specify information about the dimensionality of an input port.
Syntax void ssSetInputPortDimensionInfo(SimStruct *S, int_T port,
DimsInfo_T *dimsInfo)
Arguments S
SimStruct representing an S-function block.
port
Index of an input port
dimsInfo
Structure of type DimsInfo_T that specifies the dimensionality of the signals
accepted by port.
The structure is defined as
typedef struct DimsInfo_tag{
int width;/* number of elements */
int numDims/* Number of dimensions */
int *dims;/* Dimensions. */
[snip]
}DimsInfo_T;
where:
numDims specifies the number of dimensions of the signal, e.g., 1 for a 1-D
(vector) signal or 2 for a 2-D (matrix) signal, or DYNAMICALLY_SIZED if the
number of dimensions is determined dynamically
dims is an integer array that specifies the size of each dimension, e.g., [2 3]
for a 2-by-3 matrix signal, or DYNAMICALLY_SIZED for each dimension that
is determined dynamically, e.g., [2 DYNAMICALL_SIZED]
width equals the total number of elements in the signal, e.g., 12 for a 3-by-4
matrix signal or 8 for an 8-element vector signal, or DYNAMICALLY_SIZED if
the total number of elements is determined dynamically
Note Use the macro, DECL_AND_INIT_DIMSINFO, to declare and initialize an
instance of this structure.
10-158
ssSetInputPortDimensionInfo
Description Specifies the dimension information for port. Use this function in
mdlInitializeSizes to initialize the input port dimension information. If you
want the port to inherit its dimensions from the port to which it is connected,
specify DYNAMIC_DIMENSION as the dimsInfo for port.
Languages C
Example The following example specifies that input port 0 accepts 2-by-2 matrix signals.
{
DECL_AND_INIT_DIMSINFO(di);
int dims[2];
di.numDims = 2;
dims[0] = 2;
dims[1] = 2;
di.dims = &dims;
di.width = 4;
ssSetInputPortDimensionInfo(S, 0, &di);
}
See Also ssSetInputPortMatrixDimensions, ssSetInputPortVectorDimension
10-159
ssSetInputPortDirectFeedThrough
10ssSetInputPortDirectFeedThrough
Purpose Specify the direct feedthrough status of a block’s ports.
C Syntax void ssSetInputPortDirectFeedThrough(SimStruct *S, int_T port,
int_T dirFeed)
Ada Syntax procedure ssSetInputPortDirectFeedThrough(S : in SimStruct; port :
in Integer := 0; dirFeed : in Boolean);
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of the input port whose direct feedthrough property is being set.
dirFeed
Direct feedthrough status of block specified by port.
Description Use in mdlInitializeSizes (after ssSetNumInputPorts) to specify the direct
feedthrough (0 or 1) for each input port index. If not specified, the default direct
feedthrough is 0. Setting direct feedthrough to 0 for an input port is equivalent
to saying that the corresponding input port signal is not used in mdlOutputs or
mdlGetTimeOfNextVarHit. If it is used, you might or might not see a delay of
one simulation step in the input signal. This might cause the simulation solver
to issue an error due to simulation inconsistencies.
Languages Ada, C
See Also ssGetInputPortDirectFeedThrough
10-160
ssSetInputPortFrameData
10ssSetInputPortFrameData
Purpose Specify whether a port accepts signal frames.
Syntax void ssSetInputPortFrameData(SimStruct *S, int_T port,
int_T acceptsFrames)
Arguments S
SimStruct representing an S-Function block.
port
Index of an input port.
acceptsFrames
Type of signal accepted by port. Acceptable values are -1 (either frame or
unframed input), 0 (unframed input only), and 1 (framed input only).
Description Use in mdlSetInputPortFrameData to specify whether a port accepts frame
data only, unframed data only, or both.
Languages C
See Also ssGetInputPortFrameData, mdlSetInputPortFrameData
10-161
ssSetInputPortMatrixDimensions
10ssSetInputPortMatrixDimensions
Purpose Specify dimension information for an input port that accepts matrix signals.
Syntax int_T ssSetInputPortMatrixDimensions(SimStruct *S, int_T port,
int_T m, int_T n)
Arguments S
SimStruct representing an S-Function block.
port
Index of an input port.
m
Row dimension of matrix signals accepted by port or DYNAMICALLY_SIZED.
n
Column dimension of matrix signals accepted by port or DYNAMICALLY_SIZED.
Description Specifies that port accepts an m-by-n matrix signal. If either dimension is
DYNAMICALLY_SIZED, the other must be DYNAMICALLY_SIZED or 1. Returns 1 if
successful; otherwise, 0.
Languages C
Example The following example specifies that input port 0 accepts 2-by-2 matrix signals.
ssSetInputPortMatrixDimensions(S, 0, 2, 2);
10-162
ssSetInputPortOffsetTime
10ssSetInputPortOffsetTime
Purpose Specify the offset time of an input port.
Syntax void ssSetInputPortOffsetTime(SimStruct *S,
int_T inputPortIdx, int_T period)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
inputPortIdx
Index of the input port whose offset time is being set.
offset
Offset time.
Description Use in mdlInitializeSizes (after ssSetNumInputPorts) to specify the sample
time offset for each input port index. You can use this macro in conjunction with
ssSetInputPortSampleTime if you have specified port-based sample times for
your S-function.
Languages C
See Also ssSetNumInputPorts, ssSetInputPortSampleTime
10-163
ssSetInputPortOverWritable
10ssSetInputPortOverWritable
Purpose Specify whether an input port can be overwritten.
C Syntax void ssSetInputPortOverWritable(SimStruct *S, int_T port, int_T
isOverwritable)
Ada Syntax procedure ssSetInputPortOverWritable(S : in SimStruct; port : in
Integer := 0; isOverwritable : in Boolean);
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of the input port whose overwritability is being set.
isOverwritable
Value specifying whether port is overwritable.
Description Use in mdlInitializeSizes (after ssSetNumInputPorts) to specify whether
the input port is overwritable by an output port. The default is
isOverwritable=0, which means that the input port does not share memory
with an output port. When isOverwritable=1, the input port shares memory
with an output port.
Note ssSetInputPortReusable and ssSetOutputPortReusable must both be
set to 1, meaning that neither port involved can have global and persistent
memory.
Languages Ada, C
See Also ssSetNumInputPorts, ssSetInputPortReusable, ssSetOutputPortReusable,
ssGetInputPortBufferDstPort
10-164
ssSetInputPortRequiredContiguous
10ssSetInputPortRequiredContiguous
Purpose Specify that the signal elements entering a port must be contiguous.
Syntax void ssSetInputPortRequiredContiguous(SimStruct *S, int_T port,
int_T flag)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of an input port.
flag
True if signal elements must be contiguous.
Description Specifies that the signal elements entering the specified port must occupy
contiguous areas of memory. This allows a method to access the elements of the
signal simply by incrementing the signal pointer returned by
ssGetInputPortSignal. The S-function can set the value of this attribute as
early as in the mdlInitializeSizes method and at the latest in the
mdlSetWorkWidths method.
Note The default setting for this flag is false. Hence, the default method for
accessing the input signals is ssGetInputSignalPtrs.
Languages C, C++
See Also mdlInitializeSizes, mdlSetWorkWidths, ssGetInputPortSignal,
ssGetInputPortSignalPtrs
10-165
ssSetInputPortReusable
10ssSetInputPortReusable
Purpose Specify whether where memory allocated to port is reusable.
Syntax void ssSetInputPortReusable(SimStruct *S, int_T port, int_T
isReusable)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of the input port whose reusability is being set.
isReusable
Value specifying whether port is reusable.
Description Use in mdlInitializeSizes (after ssSetNumInputPorts) to specify whether
the input port memory buffer can be reused by other signals in the model. This
macro can take one of two values:
Off (isReusable=0) specifies that the input port is not reusable. This is the
default.
On (isReusable=1) specifies that the input port is reusable.
In Simulink, reusable signals share the same memory space. When this macro
is turned on, the input port signal to the S-function can be reused by other
signals in the model. This reuse results in less memory use during Simulink
simulation and more efficiency in the Real-Time Workshop generated code.
You must use caution when using this macro; you can safely turn it on only if
the S-function reads its input port signal in its mdlOutputs routine and does
not access this input port signal until the next call to mdlOutputs.
When an S-function’s input port signal is reused, other signals in the model
overwrite it prior to the execution of mdlUpdate, mdlDerivatives, or other
run-time S-function routines. For example, if the S-function reads the input
port signal in its mdlUpdate routine, or reads the input port signal in the
mdlOutputs routine and expects this value to be persistent until the execution
of its mdlUpdate routine, turning this attribute on is incorrect and leads to
erroneous results.
The default setting, off, is safe. It prevents any reuse of the S-function input
port signals, which means that the inport port signals have the same values in
10-166
ssSetInputPortReusable
any run-time S-function routine during a single execution of the simulation
loop.
Note that this is a suggestion and not a requirement for the Simulink engine.
If Simulink cannot resolve buffer reuse in local memory, it resets value=0 and
places the input port signals into global memory.
Languages C
See Also ssSetNumInputPorts, ssSetInputPortOverwritable,
ssSetOutputPortReusable
10-167
ssSetInputPortSampleTime
10ssSetInputPortSampleTime
Purpose Specify the sample time of an input port.
Syntax ssSetInputPortSampleTime(SimStruct *S,inputPortIdx,period)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
inputPortIdx
Index of the input port whose sample time is being set.
period
Sample period.
Description Use in mdlInitializeSizes (after ssSetNumInputPorts) to specify the sample
time period as continuous or as a discrete value for each input port. Input port
index numbers start at 0 and end at the total number of input ports minus 1.
You should use this macro only if you have specified port-based sample times.
Languages C
See Also ssSetNumInputPorts, ssSetInputPortOffsetTime
10-168
ssSetInputPortSampleTimeIndex
10ssSetInputPortSampleTimeIndex
Purpose Specify the sample time index of an input port.
Syntax void ssSetInputPortSampleTimeIndex(SimStruct *S,
int_T inputPortIdx, int_T sampleTimeIdx)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
inputPortIdx
Index of the input port whose sample time index is being set.
sampleTimeIdx
Sample time index.
Description Use in mdlInitializeSizes (after ssSetNumInputPorts) to specify the index of
the sample time for the port to be used in mdlOutputs and mdlOutputs when
checking for sample hits.
Note This should only be used when the PORT_BASED_SAMPLE_TIMES has been
specified for ssSetNumSampleTimes in mdlInitializeSizes.
Languages C, C++
See Also ssGetInputPortSampleTimeIndex, mdlInitializeSizes,
ssSetNumInputPorts, mdlOutputs, mdlOutputs
10-169
ssSetInputPortVectorDimension
10ssSetInputPortVectorDimension
Purpose Specify dimension information for an input port that accepts vector signals.
Syntax int_T ssSetInputPortVectorDimension(SimStruct *S, int_T port, int_T
w)
Arguments S
SimStruct representing an S-Function block.
port
Index of an input port.
w
Width of vector or DYNAMICALLY_SIZED.
Description Specifies that port accepts a w-element vector signal. Returns 1 if successful;
otherwise, 0.
Note This macro and ssSetInputPortWidth are functionally identical.
Languages C
Example The following example specifies that input port 0 accepts an 8-element matrix
signal.
ssSetInputPortVectorDimension(S, 0, 8);
See Also ssSetInputPortWidth
10-170
ssSetInputPortWidth
10ssSetInputPortWidth
Purpose Specify the width of an input port.
C Syntax void ssSetInputPortWidth(SimStruct *S, int_T port, int_T width)
Ada Syntax procedure ssSetInputPortWidth (S : in SimStruct;
port : in Integer := 0; width : in Integer);
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of the input port whose width is being set.
width
Width of the input port.
Description Use in mdlInitializeSizes (after ssSetNumInputPorts) to specify a nonzero
positive integer width or DYNAMICALLY_SIZED for each input port index starting
at 0.
Languages Ada, C
See Also ssSetNumInputPorts, ssSetOutputPortWidth
10-171
ssSetIWorkValue
10ssSetIWorkValue
Purpose Set an element of a block’s integer work vector.
Syntax int_T ssSetIWorkValue(SimStruct *S, int_T idx, int_T value)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the element to be set
value
New value of element
Description Sets the idx element of S’s integer work vector to value. The vector consists of
elements of type int_T and is of length ssGetNumIWork(S). Typically, this
vector is initialized in mdlStart or mdlInitializeConditions, updated in
mdlUpdate, and used in mdlOutputs. You can use this macro in the simulation
loop, mdlInitializeConditions, or mdlStart routines. This macro returns the
value that it sets.
Example The following statement
ssSetIWorkValue(s, 0, 1);
sets the first element of the work vector to 1.
Languages C
See Also ssGetNumIWork, ssGetIWork, ssGetIWorkValue
10-172
ssSetModeVectorValue
10ssSetModeVectorValue
Purpose Set an element of a block’s mode vector.
Syntax void ssSetModeVectorValue(SimStruct *S, int_T element, int_T value)
Arguments S
SimStruct representing an S-Function block.
element
Index of a mode vector element.
value
Mode vector value.
Description Sets the specified mode vector element to the specified value.
Languages C, C++
See Also ssGetModeVectorValue, ssGetModeVector
10-173
ssSetNumContStates
10ssSetNumContStates
Purpose Specify the number of continuous states that a block has.
C Syntax void ssSetNumContStates(SimStruct *S, int_T n)
Ada Syntax procedure ssSetNumContStates(S : in SimStruct; n : in Integer);
Arguments S
SimStruct representing an S-Function block.
n
Number of continuous states to be set for the block represented by S.
Description Use in mdlInitializeSizes to specify the number of continuous states as 0, a
positive integer, or DYNAMICALLY_SIZED. If you specify DYNAMICALLY_SIZED, you
can specify the true (positive integer) width in mdlSetWorkWidths; otherwise,
the width used is the width of the signal passing through the block. If your
S-function has continuous states, it needs to return the derivatives of the states
in mdlDerivatives so that the solvers can integrate them. Continuous states
are logged if the States option is selected on the Workspace I/O pane of the
Simulation Parameters dialog box.
Languages Ada, C
See Also ssSetNumDiscStates, ssGetNumContStates
10-174
ssSetNumDiscStates
10ssSetNumDiscStates
Purpose Specify the number of discrete states that a block has.
Syntax ssSetNumDiscStates(SimStruct *S, int_T nDiscStates)
Arguments S
SimStruct representing an S-Function block.
nDiscStates
Number of discrete states to be set for the block represented by S.
Description Use in mdlInitializeSizes to specify the number of discrete states as 0, a
positive integer, or DYNAMICALLY_SIZED. If you specify DYNAMICALLY_SIZED, you
can specify the true (positive integer) width in mdlSetWorkWidths; otherwise,
the width used is the width of the signal passing through the block. If your
S-function has discrete states, it should return the next discrete state (in place)
in mdlUpdate. Discrete states are logged if the States option is selected on the
Workspace I/O page of the Simulation Parameters dialog box.
Languages C
See Also ssSetNumContStates, ssGetNumDiscStates
10-175
ssSetNumDWork
10ssSetNumDWork
Purpose Specify the number of data type work vectors used by a block.
Syntax void ssSetNumDWork(SimStruct *S, int_T nDWork)
Arguments S
SimStruct representing an S-Function block.
nDWork
Number of data type work vectors.
Description Use in mdlInitializeSizes to specify the number of data type work vectors as
0, a positive integer, or DYNAMICALLY_SIZED. If you specify DYNAMICALLY_SIZED,
you can specify the true (positive integer) number of vectors in
mdlSetWorkWidths.
You can specify the size and data type of each work vector, using the macros
ssSetDWorkWidth and ssSetDWorkDataType, respectively. You can also specify
that the work vector holds complex values, using ssSetDWorkComplexSignal.
Languages C, C++
See Also ssGetNumDWork, ssSetDWorkWidth, ssSetDWorkDataType,
ssSetDWorkComplexSignal
10-176
ssSetNumInputPorts
10ssSetNumInputPorts
Purpose Specify the number of input ports that a block has.
C Syntax void ssSetNumInputPorts(SimStruct *S, int_T nInputPorts)
Ada Syntax procedure ssSetNumInputPorts(S : in SimStruct;
nInputPorts : in Integer);
Arguments S
SimStruct representing an S-Function block.
nInputPorts
Number of input ports on the block represented by S. Must be a nonnegative
integer.
Description Use in mdlInitializeSizes to set the number of input ports to a nonnegative
integer. Invoke it using
if (!ssSetNumInputPorts(S,nInputPorts)) return;
where ssSetNumInputPorts returns 0 if nInputPorts is negative or an error
occurs while creating the ports. When this happens, Simulink displays an
error.
Languages Ada, C
See Also ssSetInputPortWidth, ssSetNumOutputPorts
10-177
ssSetNumIWork
10ssSetNumIWork
Purpose Specify the size of a block’s integer work vector.
Syntax void ssSetNumIWork(SimStruct *S, int_T nIWork)
Arguments S
SimStruct representing an S-Function block.
nIWork
Number of elements in the integer work vector.
Description Use in mdlInitializeSizes to specify the number of int_T work vector
elements as 0, a positive integer, or DYNAMICALLY_SIZED. If you specify
DYNAMICALLY_SIZED, you can specify the true (positive integer) width in
mdlSetWorkWidths; otherwise, the width used is the width of the signal passing
through the block.
Languages C
See Also ssSetNumRWork, ssSetNumPWork
10-178
ssSetNumModes
10ssSetNumModes
Purpose Specifies the size of the block’s mode vector.
Syntax ssSetNumModes(SimStruct *S,nModes)
Arguments S
SimStruct representing an S-Function block.
nModes
Size of the mode vector for the block represented by S. Valid values are 0, a
positive integer, or DYNAMICALLY_SIZED.
Description Sets the size of the block’s mode vector to nModes. If nModes is
DYNAMICALLY_SIZED, you can specify the true (positive integer) width in
mdlSetWorkWidths; otherwise, the width used is the width of the signal passing
through the block. Use this macro in mdlInitializeSizes to specify the
number of int_T elements in the mode vector. Simulink allocates the mode
vector and initializes its elements to 0. If the default value of 0 is not
appropriate, you can set the elements of the array to other initial values in
mdlInitializeConditions. Use ssGetModeVector to access the mode vector.
The mode vector, combined with zero-crossing detection, allows you to create
blocks that have distinct operating modes, depending on the current values of
input or output signals. For example, consider a block that outputs the absolute
value of its input. Such a block operates in two distinct modes, depending on
whether its input is positive or negative. If the input is positive, the block
outputs the input unchanged. If the input is negative, the block outputs the
negative of the input. You can use zero-crossing detection to detect when the
input changes sign and update the single-element mode vector accordingly (for
example, by setting its element to 0 for negative input and 1 for positive input).
You can then use the mode vector in mdlOutputs to determine the mode in
which the block is currently operating.
Languages C
See Also ssGetNumModes, ssGetModeVector
10-179
ssSetNumNonsampledZCs
10ssSetNumNonsampledZCs
Purpose Specify the number of states for which a block detects zero crossings that occur
between sample points.
Syntax ssSetNumNonsampledZCs(SimStruct *S, nNonsampledZCs)
Arguments S
SimStruct representing an S-Function block.
nNonsampledZCs
Number of nonsampled zero crossings that a block detects.
Description Use in mdlInitializeSizes to specify the number of states for which the block
detects nonsampled zero crossings (real_T) as 0, a positive integer, or
DYNAMICALLY_SIZED. If you specify DYNAMICALLY_SIZED, you can specify the
true (positive integer) width in mdlSetWorkWidths; otherwise, the width used
is the width of the signal passing through the block.
Languages C
See Also ssSetNumModes
10-180
ssSetNumOutputPorts
10ssSetNumOutputPorts
Purpose Specify the number of output ports that a block has.
C Syntax void ssSetNumOutputPorts(SimStruct *S, int_T nOutputPorts)
Ada Syntax procedure ssSetNumOutputPorts(S : in SimStruct;
nOutputPorts : in Integer);
Arguments S
SimStruct representing an S-Function block.
nOutputPorts
Number of output ports on the block represented by S. Must be a nonnegative
integer.
Description Use in mdlInitializeSizes to set the number of output ports to a nonnegative
integer. It should be invoked using
if (!ssSetNumOutputPorts(S,nOutputPorts)) return;
where ssSetNumOutputPorts returns 0 if nOutputPorts is negative or an error
occurs while creating the ports. When this occurs, and you return out of your
S-function, Simulink displays an error message.
Languages Ada, C
See Also ssSetInputPortWidth, ssSetNumInputPorts
10-181
ssSetNumPWork
10ssSetNumPWork
Purpose Specify the size of a block’s pointer work vector.
Syntax void ssSetNumPWork(SimStruct *S, int_T nPWork)
Arguments S
SimStruct representing an S-Function block.
nPWork
Number of elements to be allocated to the pointer work vector of the block
represented by S.
Description Use in mdlInitializeSizes to specify the number of pointer (void *) work
vector elements as 0, a positive integer, or DYNAMICALLY_SIZED. If you specify
DYNAMICALLY_SIZED, you can specify the true (positive integer) width in
mdlSetWorkWidths; otherwise, the width used is the width of the signal passing
through the block.
Languages C
See Also ssGetNumPWork
10-182
ssSetNumRunTimeParams
10ssSetNumRunTimeParams
Purpose Specify the number of run-time parameters created by this S-function.
Syntax void ssSetNumRunTimeParams(S, int_T num)
Arguments S
SimStruct representing an S-Function block.
num
Number of run-time parameters.
Description Use this function in mdlSetWorkWidths to specify the number of run-time
parameters created by this S-function.
Languages C
See Also mdlSetWorkWidths, ssGetNumRunTimeParams, ssSetRunTimeParamInfo
10-183
ssSetNumRWork
10ssSetNumRWork
Purpose Specify the size of a block’s floating-point work vector.
Syntax void ssSetNumRWork(SimStruct *S, int_T nRWork)
Arguments S
SimStruct representing an S-Function block.
nRWork
Number of elements in the floating-point work vector.
Description Use in mdlInitializeSizes to specify the number of real_T work vector
elements as 0, a positive integer, or DYNAMICALLY_SIZED. If you specify
DYNAMICALLY_SIZED, you can specify the true (positive integer) width in
mdlSetWorkWidths; otherwise, the width used is the width of the signal passing
through the block.
Languages C
See Also ssSetNumIWork, ssSetNumPWork
10-184
ssSetNumSampleTimes
10ssSetNumSampleTimes
Purpose Specify the number of sample times that an S-Function block has.
Syntax void ssSetNumSampleTimes(SimStruct *S, int_T nSampleTimes)
Arguments S
SimStruct representing an S-Function block.
nSampleTimes
Number of sample times that S has.
Description Use in mdlInitializeSizes to set the number of sample times S has. This
must be a positive integer greater than 0.
Languages C
See Also ssGetNumSampleTimes
10-185
ssSetNumSFcnParams
10ssSetNumSFcnParams
Purpose Specify the number of parameters that an S-Function block has.
Syntax ssSetNumSFcnParams(SimStruct *S, int_T nSFcnParams)
Arguments S
SimStruct representing an S-Function block.
nSFcnParams
Number of parameters that S has.
Description Use in mdlInitializeSizes to set the number of S-function parameters.
Languages C
See Also ssGetNumSFcnParams
10-186
ssSetOffsetTime
10ssSetOffsetTime
Purpose Set the offset time of a block.
Syntax ssSetOffsetTime(SimStruct *S, st_index, period)
Arguments S
SimStruct representing an S-Function block.
st_index
Index of the sample time whose offset is to be set.
offset
Offset of the sample time specified by st_index.
Description Use this macro in mdlInitializeSizes to specify the offset of the sample time
where st_index starts at 0.
Languages C
See Also ssSetSampleTime, ssSetInputPortOffsetTime, ssSetOutputPortOffsetTime
10-187
ssSetOptions
10ssSetOptions
Purpose Specify S-function options.
Syntax void ssSetOptions(SimStruct *S, uint_T options)
Arguments S
SimStruct representing an S-Function block.
options
Options.
Description Use in mdlInitializeSizes to specify S-function options (see following). The
options must be joined using the OR operator. For example:
ssSetOption(S, (SS_OPTION_EXCEPTION_FREE_CODE |
SS_OPTION_DISCRETE_VALUED_OUTPUT));
S-Function Options
An S-function can specify the following options, using ssSetOptions:
SS_OPTION_EXCEPTION_FREE_CODE
If your S-function does not use mexErrMsgTxt, mxCalloc, or any other
routines that can throw an exception when called, you can set this option for
improved performance.
SS_OPTION_RUNTIME_EXCEPTION_FREE_CODE
Similar to SS_OPTION_EXCEPTION_FREE_CODE except it only applies to the
run-time routines mdlGetTimeOfNextVarHit, mdlOutputs, mdlUpdate, and
mdlDerivatives.
SS_OPTION_DISCRETE_VALUED_OUTPUT
Specify this if your S-function has discrete valued outputs. This is checked
when your S-function is placed within an algebraic loop. If your S-function
has discrete valued outputs, its outputs are not assigned algebraic variables.
SS_OPTION_PLACE_ASAP
Use to specify that your S-function should be placed as soon as possible. This
is typically used by devices connecting to hardware.
SS_OPTION_ALLOW_INPUT_SCALAR_EXPANSION
Use to specify that the input to your S-function input ports can be either 1 or
the size specified by the port, which is usually referred to as the block width.
10-188
ssSetOptions
SS_OPTION_DISALLOW_CONSTANT_SAMPLE_TIME
Use to disable an S-Function block from inheriting a constant sample time.
SS_OPTION_ASYNCHRONOUS
This option applies only to S-functions that have 0 or 1 input ports and 1
output port. The output port must be configured to perform function calls on
every element. If any of these requirements is not met, the
SS_OPTION_ASYNCHRONOUS option is ignored. Use this option when driving
function-call subsystems to attached to interrupt service routines.
SS_OPTION_ASYNC_RATE_TRANSITION
Use this option to create a read-write pair of blocks intended to guarantee
correct data transfers between a synchronously and an asynchronously
executing subsystem or between two asynchronously executing subsystems.
Both your “read” S-function and your “write” S-function should set this
option. See the comment for SS_OPTION_ASYNC_RATE_TRANSITION in
symstruc.h for more information.
SS_OPTION_PORT_SAMPLE_TIMES_ASSIGNED
Use this when you have registered multiple sample times
(ssSetNumSampleTimes > 1) to specify the rate at which each input and
output port is running. The simulation engine needs this information when
checking for illegal rate transitions.
SS_OPTION_SFUNCTION_INLINED_FOR_RTW
Set this if you have a .tlc file for your S-function and do not have an mdlRTW
method. Setting this option has no effect if you have an mdlRTW method.
SS_OPTION_ALLOW_PARTIAL_DIMENSIONS_CALL
Indicates that the S-function can handle dynamically dimensioned signals.
See mdlSetDefaultPortDimensionInfo for more information.
SS_OPTION_FORCE_NONINLINED_FCNCALL
Use this flag if the block requires that all function-call subsystems that it
calls should be generated as procedures instead of possibly being generated
as inlined code.
SS_OPTION_USE_TLC_WITH_ACCELERATOR
Use this to force the Accelerator to use the TLC inlining code for an
S-function, which speeds up execution of the S-function. By default, the
Accelerator uses the mex version of the S-function even though a TLC file for
the S-function exists. This option should not be set for device driver blocks
10-189
ssSetOptions
(A/D) or when there is an incompatibility between running the mex Start/
InitializeConditions functions together with the TLC Outputs/Update/
Derivatives.
SS_OPTION_SIM_VIEWING_DEVICE
This S-function is a SimViewingDevice. As long as it meets the other
requirements for this type of block (no states, no outputs, etc.), it is
considered to be an external mode block (it show up in the external mode GUI
and no code is generated for it). During an external mode simulation, this
block is run on the host only.
SS_OPTION_CALL_TERMINATE_ON_EXIT
This option allows S-function authors to better manage the data cached in
run-time parameters and UserData. Setting this option guarantees that the
mdlTerminate function is called if mdlInitializeSizes is called. This means
that mdlTerminate is called
- When a simulation ends
Note that it does not matter if the simulation fails and at what stage the
simulation fails. Therefore, if the mdlSetWorkWidths of some block errors
out, the model’s other blocks have a chance to free the memory during a
call to mdlTerminate.
- Every time an S-Function block is destroyed
- If the user is editing the S-function graphically
- If the S-Function block was reduced as a result of invoking
ssSetBlockReduction
If this option is not set, mdlTerminate is called only if at least one of the
blocks has had its mdlStart called.
10-190
ssSetOptions
SS_OPTION_REQ_INPUT_SAMPLE_TIME_MATCH
Use this to option to specify that the input signal sample times match the
sample time assigned to the block input port. For example:
generates an error if this option is set. If the block (or input port) sample time
is inherited, no error is generated.
SS_OPTION_WORKS_WITH_CODE_REUSE
Signifies that this S-function is compatible with the subsystem code reuse
feature of the Real-Time Workshop (see “Creating Code-Reuse-Compatible
S-Functions” on page 8-42).
SS_OPTION_ALLOW_CONSTANT_PORT_SAMPLE_TIME
Set this option in mdlInitializeSizes to allow your S-function’s ports to
specify or inherit a constant sample time (see “Specifying Constant Sample
Time for a Port” on page 7-20 for more information).
SS_OPTION_ALLOW_PORT_BASED_SAMPLE_TIME_IN_TRIGSS
Set this option in mdlInitializeSizes to allow an S-function that uses
port-based sample times to operate in a triggered subsystem (see
“Configuring Port-Based Sample Times for Use in Triggered Subsystems” on
page 7-21 for more information).
Languages C, C++
src(0.1)
S-function
Port-based Ts = 1
10-191
ssSetOutputPortComplexSignal
10ssSetOutputPortComplexSignal
Purpose Set the numeric type (real or complex) of an output port.
Syntax void ssSetOutputPortComplexSignal(SimStruct *S, input_T port,
CSignal_T csig)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
port
Index of an output port.
csignal
Numeric type of the signals emitted by port. Valid values are COMPLEX_NO (real
signal), COMPLEX_YES (complex signal), and COMPLEX_INHERITED (dynamically
determined).
Description Use this function in mdlInitializeSizes to initialize an input port signal type.
If the numeric type of the input port is determined dynamically, e.g., by a
parameter setting, set the numeric type to COMPLEX_INHERITED. The default
numeric type of an output port is real.
Languages C
Example Assume that an S-function has three output ports. The first output port emits
real (noncomplex) signals. The second input port emits a complex signal. The
third port emits signals of a type determined by a parameter setting. The
following example specifies the correct numeric type for each port.
ssSetOutputPortComplexSignal(S, 0, COMPLEX_NO)
ssSetOutputPortComplexSignal(S, 1, COMPLEX_YES)
ssSetOutputPortComplexSignal(S, 2, COMPLEX_INHERITED)
See Also ssGetOutputPortComplexSignal
10-192
ssSetOutputPortDataType
10ssSetOutputPortDataType
Purpose Set the data type of an output port.
C Syntax void ssSetOutputPortDataType(SimStruct *S, int_T port, DTypeId id)
Ada Syntax procedure ssSetOutputPortDataType(S : in SimStruct;
port : in Integer := 0; id : in Integer);
Arguments
S
SimStruct representing an S-Function block or a Simulink model.
port
Index of an output port.
id
ID of the data type accepted by port.
Description Use this function in mdlInitializeSizes to set the data type of the output port
specified by port. If the output port’s data type is determined dynamically, for
example, from the data type of a block parameter, set the data type to
DYNAMICALLY_TYPED.
Note The data type of an output port is double (real_T) by default.
Languages Ada, C
Example Suppose that you want to create an S-function with two output ports, the first
of which gets its data type from a block parameter and the second of which
outputs signals of type int16_T. The following code sets up the data types.
ssSetOutputPortDataType(S, 0, DYNAMICALLY_TYPED)
ssSetOutputPortDataType(S, 1, SS_INT16)
See Also ssGetOutputPortDataType
10-193
ssSetOutputPortDimensionInfo
10ssSetOutputPortDimensionInfo
Purpose Specify information about the dimensionality of an output port.
Syntax void ssSetInputPortDimensionInfoSimStruct *S, int_T port,
DimsInfo_T *dimsInfo)
Arguments S
SimStruct representing an S-function block.
port
Index of an output port
dimsInfo
Structure of type DimsInfo_T that specifies the dimensionality of the signals
emitted by port
See ssSetInputPortDimensionInfo for a description of this structure.
Description Specifies the dimension information for port. Use this function in
mdlInitializeSizes to initialize the output port dimension info. If you want
the port to inherit its dimensionality from the block to which it is connected,
specify DYNAMIC_DIMENSION as the dimsInfo for port.
Languages C
Example The following example specifies that input port 0 accepts 2-by-2 matrix signals.
DECL_AND_INIT_DIMSINFO(di);
di.numDims = 2;
int dims[2];
dims[0] = 2;
dims[1] = 2;
di.dims = &dims;
di.width = 4;
ssSetOutputPortDimensionInfo(S, 0, &di);
See Also ssSetInputPortDimensionInfo
10-194
ssSetOutputPortFrameData
10ssSetOutputPortFrameData
Purpose Specify whether a port outputs framed data.
Syntax void ssSetOutputPortFrameData(SimStruct *S, int_T port,
int_T outputsFrames)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
outputsFrames
Type of signal output by port. Acceptable values are -1 (either frame or
unframed input), 0 (unframed input only), and 1 (framed input only).
Description Use in mdlSetInputPortFrameData to specify whether an output port issues
frame data only, unframed data only, or both.
Languages C
See Also ssGetOutputPortFrameData, mdlSetInputPortFrameData
10-195
ssSetOutputPortMatrixDimensions
10ssSetOutputPortMatrixDimensions
Purpose Specify dimension information for an output port that emits matrix signals.
Syntax int_T ssSetOutputPortMatrixDimensions(SimStruct *S, int_T port,
int_T m, in_T n)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
m
Row dimension of matrix signals emitted by port or DYNAMICALLY_SIZED.
n
Column dimension of matrix signals emitted by port or DYNAMICALLY_SIZED.
Description Specifies that port emits an m-by-n matrix signal. If either dimension is
DYNAMICALLY_SIZED, the other must be DYNAMICALLY_SIZED or 1. Returns 1 if
successful; otherwise, 0.
Languages C
Example The following example specifies that input port 0 emits 2-by-2 matrix signals.
ssSetOutputPortMatrixDimensions(S, 0, 2, 2);
10-196
ssSetOutputPortOffsetTime
10ssSetOutputPortOffsetTime
Purpose Specify the offset time of an output port.
Syntax ssSetOutputPortOffsetTime(SimStruct *S,outputPortIdx,offset)
Arguments S
SimStruct representing an S-Function block.
outputPortIdx
Index of the output port whose sample time is being set.
offset
Sample time of an output port.
Description Use in mdlInitializeSizes (after ssSetNumOutputPorts) to specify the
sample time offset value for each output port index. This should only be used if
you have specified the S-function’s sample times as port-based.
Languages C
See Also ssSetNumOutputPorts, ssSetOutputPortSampleTime
10-197
ssSetOutputPortReusable
10ssSetOutputPortReusable
Purpose Specify that an output port is reusable.
Syntax ssSetOutputPortReusable(SimStruct *S,outputPortIdx,isReusable)
Arguments S
SimStruct representing an S-Function block.
outputPortIdx
Index of the output port whose reusability is being set.
isReusable
Value specifying reusability of the port.
Description Use in mdlInitializeSizes (after ssSetNumOutputPorts) to specify whether
output ports have a test point. This macro can take one of two values:
Off (isReusable=0) specifies that the output port is not reusable. This is the
default.
On (isReusable=1) specifies that the output port is reusable.
In Simulink, reusable signals share the same memory space. This macro allows
an S-function to tell Simulink that it can store the S-function’s outputs
temporarily in memory used for storing other signals in the model. This reuse
results in less memory use during simulation and more efficiency in the
Real-Time Workshop generated code.
When you mark an output port as reusable, your S-function must update the
output once in mdlOutputs. It cannot expect the previous output value to be
persistent.
By default, the output port signals are not reusable. This forces Simulink’s
simulation engine (and the Real-Time Workshop) to allocate global memory for
these output port signals. Hence this memory is only written to by your
S-function and persists between model execution steps.
Note If you want to allow users to connect the output of your S-function to a
Merge block, you must use this macro to specify that your S-function’s output
ports are reusable.
10-198
ssSetOutputPortReusable
Languages C
See Also ssSetNumOutputPorts, ssSetInputPortReusable
10-199
ssSetOutputPortSampleTime
10ssSetOutputPortSampleTime
Purpose Specify the sample time of an output port.
Syntax ssSetOutputPortSampleTime(SimStruct *S,outputPortIdx,period)
Arguments S
SimStruct representing an S-Function block.
outputPortIdx
Index of the output port whose sample time is being set.
period
Sample time of output port.
Description Use in mdlInitializeSizes (after ssSetNumOutputPorts) to specify the
sample time period as continuous or as a discrete value for each output port
index. This should only be used if you have specified port-based sample times.
Languages C
See Also ssSetNumOutputPorts, ssSetOutputPortOffsetTime
10-200
ssSetOutputPortVectorDimension
10ssSetOutputPortVectorDimension
Purpose Specify dimension information for an output port that emits vector signals.
Syntax int_T ssSetOutputPortVectorDimension(SimStruct *S, int_T port,
int_T w)
Arguments S
SimStruct representing an S-Function block.
port
Index of an output port.
w
Width of vector or DYNAMICALLY_SIZED.
Description Specifies that port emits a w-element vector signal. Returns 1 if successful;
otherwise, 0.
Note This macro and ssSetOutputPortWidth are functionally identical.
Example The following example specifies that output port 0 emits an 8-element matrix
signal.
ssSetOutputPortVectorDimension(S, 0, 8);
Languages C
See Also ssSetOutputPortWidth
10-201
ssSetOutputPortWidth
10ssSetOutputPortWidth
Purpose Specify the width of an output port.
C Syntax void ssSetOutputPortWidth(SimStruct *S, int_T port, int_T width)
Ada Syntax procedure ssSetOutputPortWidth(S : in SimStruct;
port : in Integer := 0; Width : in Integer);
Arguments S
SimStruct representing an S-Function block.
port
Index of the output port whose width is being set.
width
Width of an output port.
Description Use in mdlInitializeSizes (after ssSetNumOutputPorts) to specify a nonzero
positive integer width or DYNAMICALLY_SIZED for each output port index
starting at 0.
Languages Ada, C
See Also ssSetNumOutputPorts, ssSetInputPortWidth
10-202
ssSetParameterName
10ssSetParameterName
Purpose Set the name of a parameter.
Syntax procedure ssSetParameterName(S : in SimStruct; Parameter : in
Integer; Name : in String);
Arguments S
SimStruct representing an S-Function block.
Parameter
Index of a parameter.
Name
Name of the parameter.
Description Sets the name of Parameter to Name.
Languages Ada
10-203
ssSetParameterTunable
10ssSetParameterTunable
Purpose Set the tunability of a parameter.
Syntax procedure ssSetParameterTunable(S : in SimStruct; Parameter : in
Integer; IsTunable : in Boolean);
Arguments S
SimStruct representing an S-Function block.
Parameter
Index of a parameter.
IsTunable
True indicates that the parameter is tunable.
Description Sets the tunability of Parameter to the value of IsTunable.
Languages Ada
10-204
ssSetPlacementGroup
10ssSetPlacementGroup
Purpose Specify the name of the placement group of a block.
Syntax void ssSetPlacementGroup(SimStruct *S, const char *groupName)
Arguments S
SimStruct representing an S-Function block. The block must be either a source
block (i.e., a block without input ports) or a sink block (i.e., a block without
output ports).
groupName
Name of the placement group of the block represented by S.
Description Use this macro to specify the name of the placement group to which the block
represented by S belongs. S-functions that share the same placement group
name are placed adjacent to each other in the block execution order list for the
model. This macro should be invoked in mdlInitializeSizes.
Note You typically use this macro is to create Real-Time Workshop device
driver blocks.
Languages C
See Also ssGetPlacementGroup
10-205
ssSetPWorkValue
10ssSetPWorkValue
Purpose Set an element of a block’s pointer work vector.
Syntax void* ssSetPWorkValue(SimStruct *S, int_T idx, void* pointer)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the element to be set
pointer
New pointer element
Description Sets the idx element of S’s pointer work vector to pointer. The vector consists
of elements of type void* and is of length ssGetNumPWork(S). Typically, this
vector is initialized in mdlStart or mdlInitializeConditions, updated in
mdlUpdate, and used in mdlOutputs. You can use this macro in the simulation
loop, mdlInitializeConditions, or mdlStart routines. This macro returns the
pointer that it sets.
Example The following statement
typedef struct Color_tag {int r; int b; int g;} Color;
Color* p = malloc(sizeof(Color));
ssSetPWorkValue(s, 0, p);
sets the first element of the pointer work vector to a pointer to the allocated
Color structure.
Languages C
See Also ssGetNumPWork, ssGetPWork, ssGetPWorkValue
10-206
ssSetRWorkValue
10ssSetRWorkValue
Purpose Set an element of a block’s floating-point work vector.
Syntax real_T ssSetRWorkValue(SimStruct *S, int_T idx, real_T value)
Arguments S
SimStruct representing an S-Function block.
idx
Index of the element to be set
value
New value of element
Description Sets the idx element of S’s floating-point work vector to value. The vector
consists of elements of type real_T and is of length ssGetNumRWork(S).
Typically, this vector is initialized in mdlStart or mdlInitializeConditions,
updated in mdlUpdate, and used in mdlOutputs. You can use this macro in the
simulation loop, mdlInitializeConditions, or mdlStart routines. This macro
returns the value that it sets.
Example The following statement
ssSetRWorkValue(s, 0, 1.0);
sets the first element of the work vector to 1.0.
Languages C
See Also ssGetNumRWork, ssGetRWork, ssGetRWorkValue
10-207
ssSetRunTimeParamInfo
10ssSetRunTimeParamInfo
Purpose Specify the attributes of a run-time parameter.
Syntax void ssSetRunTimeParamInfo(SimStruct *S, int_T param, ssParamRec
*info)
Arguments S
SimStruct representing an S-Function block.
param
Index of a run-time parameter.
Description Use this function in mdlSetWorkWidths or mdlProcessParameters to specify
information about a run-time parameter. Use an ssParamRec structure to pass
the parameter attributes to the function.
ssParamRec Structure
The simstruc.h macro defines this structure as follows:
typedef struct ssParamRec_tag {
const char *name;
int_T nDimensions;
int_T *dimensions;
DTypeId dataTypeId;
boolean_T complexSignal;
void *data;
const void *dataAttributes;
int_T nDlgParamIndices;
int_T *dlgParamIndices;
TransformedFlag transformed; /* Transformed status */
boolean_T outputAsMatrix; /* Write out parameter as a
vector (false)
* [default] or a matrix (true)
*/
} ssParamRec;
The record contains the following fields.
name. Name of the parameter. This must point to persistent memory. Do not
set to a local variable (static char name[32] or strings name are okay).
10-208
ssSetRunTimeParamInfo
Note The first four characters of block’s run-time parameter names must be
unique. If they are not, Simulink signals an error. For example, trying to
register a parameter named param2 triggers an error if a parameter named
param1 already exists.
nDimensions. Number of dimensions that this parameter has.
dimensions. Array giving the size of each dimension of the parameter.
dataTypeId. Data type of the parameter. For built-in data types, see
BuiltInDTypeId in simstruc_types.h.
complexSignal. Specifies whether this parameter has complex numbers (true) or
real numbers (false) as values.
data. Pointer to the value of this run-time parameter. If the parameter is a
vector or matrix or a complex number, this field points to an array of values
representing the parameter elements. Complex Simulink signals are stored
interleaved. Likewise complex run-time parameters must be stored
interleaved. Note that mxArrays stores the real and complex parts of complex
matrices as two separate contiguous pieces of data instead of interleaving the
real and complex parts.
dataAttributes. The data attributes pointer is a persistent storage location where
the S-function can store additional information describing the data and then
recover this information later (potentially in a different function).
nDlgParamIndices.
Number of dialog parameters used to compute this run-time parameter.
dlgParamIndices. Indices of dialog parameters used to compute this run-time
parameter.
transformed. Specifies the relationship between this run-time parameter and
the dialog parameters specified by dlgParamIndices. This field can have any
of the following values defined by TransformFlag in simstruc.h.
10-209
ssSetRunTimeParamInfo
RTPARAM_NOT_TRANSFORMED
Specifies that this run-time parameter corresponds to a single dialog
parameter (nDialogParamIndices is one) and has the same value as the
dialog parameter.
RTPARAM_TRANSFORMED
Specifies that the value of this run-time parameter depends on the values of
multiple dialog parameters (nDialogParamIndices > 1) or that this
run-time parameter corresponds to one dialog parameter but has a different
value or data type.
RTPARAM_MAKE_TRANSFORMED_TUNABLE
Specifies that this run-time parameter corresponds to a single tunable dialog
parameter (nDialogParamIndices is one) and that the run-time parameter’s
value or data type differs from the dialog parameter’s. During code
generation, Real-Time Workshop writes the data type and value of the
run-time parameter (rather than the dialog parameter) out to the Real-Time
Workshop file. For example, suppose that the dialog parameter contains a
workspace variable k of type double and value 1. Further, suppose the
S-function sets the data type of the corresponding run-time variable to int8
and the run-time parameter’s value to 2. In this case, during code generation,
the Real-Time Workshop writes k out to the Real-Time Workshop file as an
int8 variable with an initial value of 2.
outputAsMatrix. Specifies whether to write the values of this parameter out to
the model.rtw file as a matrix (true) or as a vector (false).
Languages C
See Also mdlSetWorkWidths, mdlProcessParameters, ssGetNumRunTimeParams,
ssGetRunTimeParamInfo
10-210
ssSetSampleTime
10ssSetSampleTime
Purpose Set the period of a sample time.
C Syntax void ssSetSampleTime(SimStruct *S, st_index, time_T period)
Ada Syntax procedure ssSetSampleTime(S : in SimStruct; Period : in time_T;
st_index : in time_T := 0.0);
Arguments S
SimStruct representing an S-Function block.
st_index
Index of the sample time whose period is to be set.
period
Period of the sample time specified by st_index.
Description Use this macro in mdlInitializeSizes to specify the period of the sample time
where st_index starts at 0.
Languages Ada, C
See Also ssSetInputPortSampleTime, ssSetOutputPortSampleTime, ssSetOffsetTime
10-211
ssSetSFcnParamNotTunable
10ssSetSFcnParamNotTunable
Purpose Make a block parameter nontunable.
Syntax void ssSetSFcnParamNotTunable(SimStruct *S, int_T index)
Arguments S
SimStruct representing an S-Function block.
index
Index of the parameter to be made nontunable.
Description Use this macro in mdlInitializeSizes to specify that a parameter doesn’t
change during the simulation, where index starts at 0 and is less than
ssGetSFcnParamsCount(S). This improves efficiency and provides error
handling in the event that an attempt is made to change the parameter.
Note This macro is obsolete. It is provided only for compatibility with
S-functions created with earlier versions of Simulink.
Languages C
See Also ssSetSFcnParamTunable, ssGetSFcnParamsCount
10-212
ssSetSFcnParamTunable
10ssSetSFcnParamTunable
Purpose Make a block parameter tunable.
Syntax void ssSetSFcnParamTunable(SimStruct *S, int_T param,
int_T isTunable)
Arguments S
SimStruct representing an S-Function block.
param
Index of the parameter.
isTunable
Valid values are 1 (tunable) or 0 (not tunable).
Description Use this macro in mdlInitializeSizes to specify whether a user can change a
dialog parameter during the simulation. The parameter index starts at 0 and
is less than ssGetSFcnParamsCount(S). This improves efficiency and provides
error handling in the event that an attempt is made to change the parameter.
Note Dialog parameters are tunable by default. However, an S-function
should declare the tunability of all parameters, whether tunable or not, to
avoid programming errors. If the user enables the simulation diagnostic
S-function upgrade needed, Simulink issues the diagnostic whenever it
encounters an S-function that fails to specify the tunability of all its
parameters.
Languages C
See Also ssGetSFcnParamsCount
10-213
ssSetSolverNeedsReset
10ssSetSolverNeedsReset
Purpose Ask Simulink to reset the solver.
Syntax void ssSetSolverNeedsReset(SimStruct *S)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
Description This macro causes the solver for the current simulation to reinitialize variable
step size and zero-crossing computations. This happens only if the solver is a
variable-step, continuous solver. (The macro has no effect if the user has
selected another type of solver for the current simulation.) An S-function
should invoke this macro whenever changes occur in the dynamics of the
S-function, e.g., a discontinuity in a state or output, that might invalidate the
solver’s step-size computations. Otherwise, the solver might take
unnecessarily small steps, slowing down the simulation.
Note If a change in the dynamics of the S-function necessitates reinitializing
its continuous states, the S-function should reinitialize the states before
invoking this macro to ensure accurate computation of the next step size.
Languages C
Example The following example uses this macro to ask Simulink to reset the solver.
static void mdlOutputs(SimStruct *S, int_T tid)
{
:
: <snip>
:
if ( under_certain_conditions ) {
double *x = ssGetContStates(S);
/* reset the states */
for (i=0; i<nContStates; i++) {
x[i] = 0.0;
}
/* Ask Simulink to reset the solver. */
ssSetSolverNeedsReset(S);
}
}
10-214
ssSetSolverNeedsReset
Also see the source code for the Time-Varying Continuous Transfer Function
(matlabroot/simulink/src/stvctf.c) for an example of where and how to use
this macro.
10-215
ssSetStopRequested
10ssSetStopRequested
Purpose Set the simulation stop requested flag.
Syntax ssSetStopRequested(SimStruct *S, val)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
val
Boolean value (int_T) specifying whether stopping the simulation has been
requested (1) or not (0).
Description Sets the simulation stop requested flag to val. If val is not 0, Simulink halts
the simulation at the end of the current time step.
Languages C
See Also ssGetStopRequested
10-216
ssSetTNext
10ssSetTNext
Purpose Set the time of the next sample hit.
Syntax void ssSetTNext(SimStruct *S, time_T tnext)
Arguments S
SimStruct representing an S-Function block.
tnext
Time of the next sample hit.
Description A discrete S-function with a variable sample time should use this macro in
mdlGetTimeOfNextVarHit to specify the time of the next sample hit.
Languages C
See Also ssGetTNext, ssGetT, mdlGetTimeOfNextVarHit
10-217
ssSetUserData
10ssSetUserData
Purpose Specify user data.
Syntax void ssSetUserData(SimStruct *S, void * data)
Arguments S
SimStruct representing an S-Function block.
data
User data.
Description Specifies user data.
Languages C, C++
See Also ssGetUserData
10-218
ssSetVectorMode
10ssSetVectorMode
Purpose Specify the vector mode that an S-function supports.
Syntax void ssSetVectorMode(SimStruct *S, ssVectorMode mode)
Arguments S
SimStruct representing an S-Function block.
mode
Vector mode.
Description Specifies the types of vector-like signals that an S-Function block’s input and
output ports support. Simulink uses this information during signal dimension
propagation to check the validity of signals connected to the block or emitted
by the block. The enumerated type ssVectorMode defines the set of values that
mode can have.
Languages C
Example See simulink/src/sfun_bitop.c for examples that use this macro.
Mode Value Signal Dimensionality Supported
SS_UNKNOWN_MODE Unknown
SS_1_D_OR_COL_VECT 1-D (vector) or single-column 2-D (column
vector)
SS_1_D_OR_ROW_VECT 1-D or single-row 2-D (row vector) signals
SS_1_D_ROW_OR_COL_VECT Vector or row or column vector
SS_1_D_VECT Vector
SS_COL_VECT Column vector
SS_ROW_VECT Row vector
10-219
ssUpdateAllTunableParamsAsRunTimeParams
10ssUpdateAllTunableParamsAsRunTimeParams
Purpose Update the values of run-time parameters to be the same as those of the
corresponding tunable dialog parameters.
Syntax void ssUpdateAllTunableParamsAsRunTimeParams(SimStruct *S)
Arguments S
Description Use this macro in the S-function’s mdlProcessParameters method to update
the values of all run-time parameters created by the
ssRegAllTunableParamsAsRunTimeParams macro.
Languages C
See Also mdlProcessParameters, ssUpdateRunTimeParamInfo,
ssRegAllTunableParamsAsRunTimeParams
10-220
ssUpdateRunTimeParamData
10ssUpdateRunTimeParamData
Purpose Update the value of a run-time parameter.
Syntax void ssUpdateRunTimeParamData(SimStruct *S, int_T param, void *data)
Arguments S
SimStruct representing an S-Function block.
param
Index of a run-time parameter.
data
New value of the parameter.
Description Use this macro in the S-function’s mdlProcessParameters method to update
the value of the run-time parameter specified by param.
Languages C
See Also mdlProcessParameters, ssGetRunTimeParamInfo,
ssUpdateAllTunableParamsAsRunTimeParams,
ssRegAllTunableParamsAsRunTimeParams
10-221
ssUpdateDlgParamAsRunTimeParam
10ssUpdateDlgParamAsRunTimeParam
Purpose Update a run-time parameter that corresponds to a dialog parameter.
Syntax ssUpdateDlgParamAsRunTimeParam(S, rtIdx)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
rtIdx
Index of the run-time parameter
Description Use in mdlProcessParameters to set the value of the run-time parameter
specified by rtIdx to the current value of the dialog parameter specified by
dlgIdx. If necessary, this function converts the data type of the value to the
data type specified by dtId.
Languages C
See Also ssUpdateAllTunableParamsAsRunTimeParams
10-222
ssUpdateRunTimeParamInfo
10ssUpdateRunTimeParamInfo
Purpose Update the attributes of a run-time parameter.
Syntax void ssUpdateRunTimeParamInfo(SimStruct *S, int_T param, ssParamRec
*info)
Arguments S
SimStruct representing an S-Function block.
param
Index of a run-time parameter.
info
Attributes of the run-time parameter.
Description Use this macro in the S-function’s mdlProcessParameters method to update
specific run-time parameters. For each parameter to be updated, the method
should first obtain a pointer to the parameter’s attributes record (ssParamRec),
using ssGetRunTimeParamInfo. The method should then update the record and
pass it back to Simulink, using this macro.
Note If you used ssRegAllTunableParamsAsRunTimeParams to create the
run-time parameters, use ssUpdateAllTunableParamsAsRunTimeParams to
update the parameters.
Languages C
See Also mdlProcessParameters, ssGetRunTimeParamInfo,
ssUpdateAllTunableParamsAsRunTimeParams,
ssRegAllTunableParamsAsRunTimeParams
10-223
ssWarning
10ssWarning
Purpose Display a warning message.
Syntax ssWarning(SimStruct *S, msg)
Arguments S
SimStruct representing an S-Function block or a Simulink model.
msg
Warning message.
Description Displays msg. Expands to mexWarnMsgTxt when compiled for use with
Simulink. When compiled for use with the Real-Time Workshop, expands to
printf("Warning:%s from '%s'\n",msg, ssGetPath(S));, if the target has
stdio facilities; otherwise, it expands to a comment.
Languages C
See Also ssSetErrorStatus, ssPrintf
10-224
ssWriteRTW2dMatParam
10ssWriteRTW2dMatParam
Purpose Write a matrix parameter to the model.rtw file.
Syntax int_T ssWriteRTW2dMatParam(SimStruct *S, const char_T *name,
const void *value, int_T dataType, int_T nRows, int_T nCols)
Arguments S
SimStruct representing an S-Function block.
name
Parameter name.
value
Parameter values.
dataType
Data type of parameter elements (see “Specifying Data Type Info” on
page 10-230).
nRows
Number of rows in the matrix.
nColumns
Number of columns in the matrix.
Description Use this function in mdlRTW to write a vector of numeric parameters to this
S-function’s model.rtw file. This function returns true if successful.
Languages C
See Also mdlRTW
10-225
ssWriteRTWMx2dMatParam
10ssWriteRTWMx2dMatParam
Purpose Write a matrix parameter in MATLAB format to the model.rtw file.
Syntax int_T ssWriteRTWMx2dMatParam(SimStruct *S, const char_T *name,
const void *rValue, const void *iValue, int_T dataType, int_T
nRows, int_T nCols)
Arguments S
SimStruct representing an S-Function block.
name
Parameter name.
rValue
Real elements of the parameter array.
iValue
Imaginary elements of the parameter array.
dataType
Data type of the parameter elements (see “Specifying Data Type Info” on
page 10-230).
nRows
Number of rows in the matrix.
nColumns
Number of columns in the matrix.
Description Use this function in mdlRTW to write a matrix parameter in MATLAB format to
this S-function’s model.rtw file. This function returns true if successful.
Languages C
See Also mdlRTW, ssWriteRTW2dMatParam
10-226
ssWriteRTWMxVectParam
10ssWriteRTWMxVectParam
Purpose Write a vector parameter in MATLAB format to the model.rtw file.
Syntax int_T ssWriteRTWMxVectParam(SimStruct *S, const char_T *name,
const void *rValue, const void *iValue, int_T dataType, int_T
size)
Arguments S
SimStruct representing an S-Function block.
name
Parameter name.
rValue
Real values of the parameter.
cValue
Complex values of the parameter.
dataType
Data type of the parameter elements (see “Specifying Data Type Info” on
page 10-230).
size
Number of elements in the vector.
Description Use this function in mdlRTW to write a vector parameter in Simulink format to
this S-function’s model.rtw file. This function returns true if successful.
Languages C
See Also mdlRTW, ssWriteRTWMxVectParam
10-227
ssWriteRTWParameters
10ssWriteRTWParameters
Purpose Write tunable parameter information to the model.rtw file.
Syntax int_T ssWriteRTWParameters(SimStruct *S, int_T nParams, int_T
paramType, const char_T *paramName, const char_T *stringInfo,
...)
Arguments S
SimStruct representing an S-Function block.
nParams
Number of tunable parameters.
paramType
Type of parameter (see “Parameter Type-Specific Arguments”).
paramName
Name of the parameter.
stringInfo
General information about the parameter, such as how it was derived.
...
Remaining arguments depend on the parameter type (see “Parameter
Type-Specific Arguments”).
Description Use this function in mdlRTW to write tunable parameter information to this
S-function’s model.rtw file. Your S-function must write the parameters out in
the same order as they are declared at the beginning of the S-function. This
function returns true if successful.
Note This function is provided for compatibility with S-functions that do not
use run-time parameters. It is suggested that you use run-time parameters
(see “Run-Time Parameters” on page 7-5). If you do use run-time parameters,
you do not need to use this function.
Parameter Type-Specific Arguments
This section lists the parameter-specific arguments required by each
parameter type.
10-228
ssWriteRTWParameters
SS_WRITE_VALUE_VECT (vector parameter)
SSWRITE_VALUE_2DMAT (matrix parameter)
SSWRITE_VALUE_DTYPE_2DMAT
SSWRITE_VALUE_DTYPE_ML_VECT
Argument Description
const real_T *valueVect Pointer to an array of vector values
int_T vectLen Length of the vector
Argument Description
const real_T *valueMat Pointer to an array of matrix elements
int_T nRows Number of rows in the matrix
int_T nCols Number of columns in the matrix
Argument Description
const real_T *valueMat Pointer to an array of matrix elements
int_T nRows Number of rows in the matrix
int_T nCols Number of columns in the matrix
int_T dtInfo Data type of matrix elements (see
“Specifying Data Type Info” on page 10-230)
Argument Description
const void *rValueVect Real component of the complex vector
const void *iValueVect Imaginary component of the complex vector
10-229
ssWriteRTWParameters
SSWRITE_VALUE_DTYPE_ML_2DMAT
Specifying Data Type Info
You obtain the data type of the value argument passed to the ssWriteRTW
macros using
DTINFO(dTypeId, isComplex)
where dTypeId can be any one of the enum values in BuiltInDTypeID
(SS_DOUBLE, SS_SINGLE, SS_INT8, SS_UINT8, SS_INT16, SS_UINT16, SS_INT32,
SS_UINT32, SS_BOOLEAN) defined in simstuc_types.h. The isComplex
argument is either 0 or 1.
For example, DTINFO(SS_INT32,0) is a noncomplex 32-bit signed integer.
If isComplex==1, the array of values is assumed to have the real and imaginary
parts arranged in an interleaved manner (i.e., Simulink format). If you prefer
to pass the real and imaginary parts as two separate arrays, you should use the
macro ssWriteRTWMxVectParam or ssWriteRTWMx2dMatParam.
Example See simulink/src/sfun_multiport.c for an example that uses this function.
int_T vectLen Length of the vector
int_T dtInfo Data type of the vector (see “Specifying
Data Type Info” on page 10-230)
Argument Description
const void *rValueMat Real component of the complex matrix
const void *iValueMat Imaginary component of the complex
matrix
int_T nRows Number of rows in the matrix
int_T nCols Number of columns in the matrix
int_T dtInfo Data type of matrix
Argument Description
10-230
ssWriteRTWParameters
Languages C
See Also mdlRTW
10-231
ssWriteRTWParamSettings
10ssWriteRTWParamSettings
Purpose Write values of nontunable parameters to the model.rtw file.
Syntax int_T ssWriteRTWParamSettings(SimStruct *S, int_T nParamSettings,
int_T paramType, const char_T *settingName, ...)
Arguments S
SimStruct representing an S-Function block.
nParamSettings
Number of parameter settings.
paramType
Type of parameter (see “Parameter Setting Type-Specific Arguments” on
page 10-232).
settingName
Name of parameter.
...
Remaining arguments depend on the parameter type (see “Parameter Setting
Type-Specific Arguments”).
Description Use this function in mdlRTW to write nontunable parameter setting information
to this S-function’s model.rtw file. A nontunable parameter is any parameter
that the S-function has declared as nontunable, using the
ssSetParameterTunable macro. You can also use this macro to write out other
constant values required to generate code for this S-function.
This function returns true if successful.
Parameter Setting Type-Specific Arguments
This section lists the parameter-specific arguments required by each
parameter type.
SSWRITE_VALUE_STR (unquoted string)
Argument Description
const char_T *value String (e.g., U.S.A.)
10-232
ssWriteRTWParamSettings
SSWRITE_VALUE_QSTR (quoted string)
SSWRITE_VALUE_VECT_STR (vector of strings)
SSWRITE_VALUE_NUM (number)
SSWRITE_VALUE_VECT (vector of numbers)
SSWRITE_VALUE_2DMAT (matrix of numbers)
Argument Description
const char_T *value String (e.g., "U.S.A.")
Argument Description
const char_T *value Vector of strings (e.g., ["USA", "Mexico"])
int_T nItemsInVect Size of the vector
Argument Description
const real_T value Number (e.g., 2)
Argument Description
const real_T *value Vector of numbers (e.g., [300, 100])
int_T vectLen Size of the vector
Argument Description
const real_T *value Matrix of numbers (e.g.,
[[170, 130],[60, 40]])
int_T nRows Number of rows in the vector
int_T nCols Number of columns in the vector
10-233
ssWriteRTWParamSettings
SSWRITE_VALUE_DTYPE_NUM (data typed number)
SSWRITE_VALUE_DTYPE_VECT (data typed vector)
SSWRITE_VALUE_DTYPE_2DMAT (data-typed matrix)
Argument Description
const void *value Number (e.g., [3+4i])
int_T dtInfo Data type (see “Specifying Data Type Info”
on page 10-230)
Argument Description
const void *value Data-typed vector (e.g., [1+2i, 3+4i])
int_T vectLen Size of the vector
int_T dtInfo Data type (see “Specifying Data Type Info”
on page 10-230)
Argument Description
const void *value Matrix (e.g., [1+2i 3+4i; 5 6])
int_T nRows Number of rows in the matrix
int_T nCols Number of columns in the matrix
int_T dtInfo Data type (see “Specifying Data Type Info”
on page 10-230)
10-234
ssWriteRTWParamSettings
SSWRITE_VALUE_DTYPE_ML_VECTOR (data-typed MATLAB vector)
SSWRITE_VALUE_DTYPE_ML_2DMAT (data typed MATLAB matrix)
Example See simulink/src/sfun_multiport.c for an example that uses this function.
Languages C
See Also mdlRTW, ssSetParameterTunable
Argument Description
const void *RValue Real component of the vector (e.g., [1 3])
const void *IValue Imaginary component of the vector
(e.g., [2 5])
int_T vectLen Number of elements in the vector
int_T dtInfo Data type (see “Specifying Data Type Info” on
page 10-230)
Argument Description
const void *RValue Real component of the matrix
(e.g., [1 5 3 6])
const void *IValue Real component of the matrix
(e.g., [2 0 4 0])
int_T nRows Number of rows in the matrix
int_T nCols Number of columns in the matrix
int_T dtInfo Data type (see “Specifying Data Type Info”
on page 10-230)
10-235
ssWriteRTWScalarParam
10ssWriteRTWScalarParam
Purpose Write a scalar parameter to the model.rtw file.
Syntax int_T ssWriteRTWScalarParam(SimStruct *S, const char_T *name,
const void *value, int_T type)
Arguments S
SimStruct representing an S-Function block.
name
Parameter name.
value
Parameter value.
type
Integer ID of the type of the parameter value, for example, the ID of one of
Simulink’s built-in data types (see BuiltInDTypeId in simstruc_types.h in
the MATLAB simulink/include subdirectory) or the ID of a user-defined type
(see “Custom Data Types” on page 7-14).
Description Use this function in mdlRTW to write scalar parameters to this S-function’s
model.rtw file. This function returns true if successful.
Languages C
See Also mdlRTW
10-236
ssWriteRTWStr
10ssWriteRTWStr
Purpose Write a string to the model.rtw file.
Syntax int_T ssWriteRTWStr(SimStruct *S, const char_T *str)
Arguments S
SimStruct representing an S-Function block.
str
String.
Description Use this function in mdlRTW to write strings to this S-function’s model.rtw file.
This function returns true if successful.
Languages C
See Also mdlRTW
10-237
ssWriteRTWStrParam
10ssWriteRTWStrParam
Purpose Write a string parameter to the model.rtw file.
Syntax int_T ssWriteRTWStrParam(SimStruct *S, const char_T *name,
const char_T *value)
Arguments S
SimStruct representing an S-Function block.
name
Parameter name.
value
Parameter value.
Description Use this function in mdlRTW to write string parameters to this S-function’s
model.rtw file. This function returns true if successful.
Languages C
See Also mdlRTW
10-238
ssWriteRTWStrVectParam
10ssWriteRTWStrVectParam
Purpose Write a string vector parameter to the model.rtw file.
Syntax int_T ssWriteRTWStrVectParam(SimStruct *S, const char_T *name,
const void *value, int_T size)
Arguments S
SimStruct representing an S-Function block.
name
Parameter name.
value
Parameter values.
size
Number of elements in the vector.
Description Use this function in mdlRTW to write a vector of string parameters to this
S-function’s model.rtw file. This function returns true if successful.
Languages C
See Also mdlRTW
10-239
ssWriteRTWVectParam
10ssWriteRTWVectParam
Purpose Write a vector parameter to the model.rtw file.
Syntax int_T ssWriteRTWVectParam(SimStruct *S, const char_T *name,
const void *value, int_T dataType, int_T size)
Arguments S
SimStruct representing an S-Function block.
name
Parameter name.
value
Parameter values.
dataType
Data type of the parameter elements (see “Specifying Data Type Info” on
page 10-230).
size
Number of elements in the vector.
Description Use this function in mdlRTW to write a vector parameter in Simulink format to
this S-function’s model.rtw file. This function returns true if successful.
Languages C
See Also mdlRTW, ssWriteRTWMxVectParam
10-240
ssWriteRTWWorkVect
10ssWriteRTWWorkVect
Purpose Write work vectors to the model.rtw file.
Syntax int_T ssWriteRTWWorkVect(SimStruct *S, const char_T *vectName,
int_T nNames, const char_T *name1, int_T size1, ...,
const char_T * nameN, int_T sizeN)
Arguments S
SimStruct representing an S-Function block.
vectName
Name of work vector (must be "RWork", "IWork", or "PWork").
nNames
***NEED DESCRIPTION***
name1 ... nameN
Names of groups of work vector elements.
size1 ... sizeN
Size of each element group (the total of the sizes must equal the size of the work
vector).
Description Use this function in mdlRTW to write work vectors to this S-function’s model.rtw
file. This function returns true if successful.
Languages C
See Also mdlRTW
10-241
ssWriteRTWWorkVect
10-242
Index
exception free code 7-33
I-1
A
Ada S-functions
creating 5-3
example 5-10
GNAT Ada95 compiler 5-9
mex syntax 5-9
source file format 5-3
specification 5-3
additional parameters for M-file S-functions 2-6
array bounds
checking 7-35
B
block I/O ports 7-8
block-based sample times 7-16
specifying 7-16
Build Info pane
S-Function Builder 3-23
C
C language header file
matlabroot/simulink/include/simstruc.h
10-2
C MEX S-functions
advantages 3-2
converting from level 1 to level 2 3-44
creating 3-3
definition 1-2
example 3-25
modes for compiling 3-34
S-Function Builder 3-5
Simulink interaction 3-35
C++ objects
making persistent 4-6
C++ S-functions
building 4-7
mex command 4-7
callback methods 1-10
CFortran 6-10
cg_sfun.h 3-33
checking array bounds 7-35
compiler compatibility
Fortran 6-7
continuous blocks
setting sample time 7-23
Continuous Derivatives pane
S-Function Builder 3-19
continuous state S-function example (C MEX)
7-36
continuous state S-function example (M-file) 2-9
creating persistent C++ objects 4-6
C-to-Fortran gateway S-function 6-7
D
data types
using user-defined 7-14
direct feedthrough 1-13
direct index lookup table example 8-24
direct-index lookup table algorithm 8-23
discrete state S-function example (C MEX) 7-41
discrete state S-function example (M-file) 2-12
Discrete Update pane
S-Function Builder 3-21
dynamically sized inputs 1-13
E
error handling
checking array bounds 7-35
Index
I-2
examples
Ada S-function specification 5-3
C MEX S-function 3-25
continuous state S-function (C MEX) 7-36
continuous state S-function (M-file) 2-9
direct index lookup table 8-24
discrete state S-function (C MEX) 7-41
discrete state S-function (M-file) 2-12
Fortran MEX S-function 6-3
hybrid system S-function (C MEX) 7-45
hybrid system S-function (M-file) 2-14
multiport S-function 8-19
pointer work vector 7-28
sample time for continuous block 7-23
sample time for hybrid block 7-24
time-varying continuous transfer function (C
MEX) 7-64
variable-step S-function (C MEX) 7-49
variable-step S-function (M-file) 2-17
zero-crossing S-function (C MEX) 7-52
exception free code 7-33
extern "C" statement 4-2
F
Fortran compilers 6-10
Fortran math library 6-9
Fortran MEX S-functions
example 6-3
template file 6-3
function-call subsystems 7-31
H
header files 3-32
hybrid blocks
setting sample time 7-24
hybrid sample times
specifying 7-22
hybrid system S-function example (C MEX) 7-45
hybrid system S-function example (M-file) 2-14
I
Initialization pane
S-Function Builder 3-8
inlined S-functions 8-19
with mdlRTW routine 8-21
input arguments for M-file S-functions 2-8
input ports
how to create 7-8
inputs, dynamically sized 1-13
L
Level 1 C MEX S-functions
converting to level 2 3-44
Libraries pane
S-Function Builder 3-13
M
masked multiport S-functions 7-12
matlabroot/simulink/include/simstruc.h C
language header file 10-2
matlabroot/simulink/src/csfunc.c example file
7-38
matlabroot/simulink/src/dsfunc.c example file
7-42
matlabroot/simulink/src/mixedm.c example file
7-46
matlabroot/simulink/src/
sfun_counter_cpp.cpp
Index
ensuring Simulink compatibility of C++
S-functions 4-2
matlabroot/simulink/src/sfun_multiport.c
example file 8-19
matlabroot/simulink/src/
sfun_timestwo_for.for Fortran example
file 6-3
matlabroot/simulink/src/sfun_zc_sat.c
example file 7-53
matlabroot/simulink/src/stvctf.c example file
7-64
matlabroot/simulink/src/vsfunc.c example file
7-49
matlabroot/toolbox/simulink/blocks/tlc_c/
sfun_multiport.tlc example file 8-19
matrix.h 3-32
mdlCheckParameters 9-2
mdlDerivatives 9-4
mdlGetTimeOfNextVarHit 9-5
mdlInitializeConditions 9-6
mdlInitializeSampleTimes 9-8
mdlInitializeSizes 9-12
and sizes structure 1-14
calling sizes 2-5
mdlOutputs 9-16
mdlProcessParameters 9-17
mdlRTW 9-19
mdlRTW routine
writing inlined S-functions 8-21
mdlSetDefaultPortComplexSignals 9-20
mdlSetDefaultPortDataTypes 9-21
mdlSetDefaultPortDimensionInfo 9-22
mdlSetInputPortComplexSignal 9-23
mdlSetInputPortDataType 9-24
mdlSetInputPortDimensionInfo 9-25
mdlSetInputPortFrameData 9-27
mdlSetInputPortSampleTime 9-28
mdlSetInputPortWidth 9-30
mdlSetOutputPortComplexSignal 9-31
mdlSetOutputPortDataType 9-32
mdlSetOutputPortDimensionInfo 9-33
mdlSetOutputPortSampleTime 9-35
mdlSetOutputPortWidth 9-36
mdlSetWorkWidths 9-37
mdlStart 9-38
mdlTerminate 9-39
mdlUpdate 9-40
mdlZeroCrossings 9-41
memory allocation 7-30
memory and work vectors 7-26
mex command
building Ada S-functions 5-9
building C MEX S-functions 3-30
building C++ S-functions 4-7
MEX S-function wrapper
definition 8-9
mex.h 3-32
M-file S-functions
arguments 2-2
creating 2-2
defining characteristics 2-5
definition 2-2
passing additional parameters 2-6
routines 2-2
multiport S-function example 8-19
multirate S-Function blocks 7-23
synchronizing 7-24
N
noninlined S-functions 8-7
I-3
Index
I-4
O
obsolete macros 3-46
options, S-function 10-188
output ports
how to create 7-10
Outputs pane
S-Function Builder 3-15
P
parameters
M-file S-functions 2-6
passing to S-functions 1-4
run-time parameters 7-5
tunable parameters 7-3
penddemo demo 1-5
persistence
C++ objects 4-6
port-based sample times 7-18
constant 7-20
inherited 7-19
specifying 7-18
triggered 7-21
R
reentrancy 7-26
RTWdata structure
inlining an S-function 8-22
run-time parameter names, uniqueness of 7-6
run-time parameters 7-5
run-time routines 7-34
S
S_FUNCTION_LEVEL 2, #define 3-31
S_FUNCTION_NAME, #define 3-31
sample times
block-based 7-16
continuous block example 7-23
hybrid block example 7-24
port-based 7-18
specifying block-based 7-15, 7-16
specifying hybrid 7-22
specifying port-based 7-18
scalar expansion of inputs 7-11
S-Function blocks
multirate 7-23
S-functions parameters field 7-2
synchronizing multirate 7-24
S-Function Builder
Build Info pane 3-23
Continuous Derivatives pane 3-19
customizing 3-8
Discrete Update pane 3-21
for C MEX S-functions 3-5
Initialization pane 3-8
Libraries pane 3-13
Outputs pane 3-15
setting the include path 3-23
S-function routines
M-file 2-2
<$nopageS-functions
<it M-file S-functions 2-2
S-functions
building C++ 4-7
C MEX 1-2
creating Ada 5-3
creating C MEX 3-3
creating Fortran 6-3
creating level 2 with Fortran 6-7
creating persistent C++ objects 4-6
creating run-time parameters 7-6
definition 1-2
Index
direct feedthrough 1-13
exception free code 7-33
fully inlined with mdlRTW routine 8-21
inlined 8-19
input arguments for M-files 2-8
level 1 and level 2 6-2
masked multiport 7-12
noninlined 8-7
options 10-188
purpose 1-5
routines 1-9
run-time parameters 7-5
run-time routines 7-34
that work with Real-Time Workshop 8-2
types of 8-3
using in models 1-3
when to use 1-5
wrapper 8-9
writing in C++ 4-2
See also Ada S-functions
See also C MEX S-functions
See also C++ S-functions
See also Fortran MEX S-functions
S-functions parameters field
S-Function block 7-2
sfuntmpl.c template 3-31
sfuntmpl.m template
M-file S-function 2-2
sfuntmpl_fortran.for template 6-3
simsizes function
M-file S-function 2-5
SimStruct 3-33
SimStruct macros 10-3
simulation loop 1-6
simulation stages 1-6
simulink.c 3-33
sizes structure
fields
M-file S-function 2-5
returned in mdlInitializeSizes 1-14
SS_OPTION_ALLOW_INPUT_SCALAR_EXPANSION
10-188
SS_OPTION_ALLOW_PARTIAL_DIMENSIONS_CALL
10-189
SS_OPTION_ASYNC_RATE_TRANSITION 10-189
SS_OPTION_ASYNCHRONOUS 10-189
SS_OPTION_CALL_TERMINATE_ON_EXIT 10-190
SS_OPTION_DISALLOW_CONSTANT_SAMPLE_TIME
10-189
SS_OPTION_DISCRETE_VALUED_OUTPUT 10-188
SS_OPTION_EXCEPTION_FREE_CODE 10-188
SS_OPTION_FORCE_NONINLINED_FCNCALL 10-189
SS_OPTION_PLACE_ASAP 10-188
SS_OPTION_RUNTIME_EXCEPTION_FREE_CODE
10-188
SS_OPTION_SIM_VIEWING_DEVICE 10-190
SS_OPTION_USE_TLC_WITH_ACCELERATOR 10-189
ssCallExternalModeFcn 10-23
ssCallSystemWithTid 10-24, 10-137
ssGetAbsTol 10-25
ssGetBlockReduction 10-26
ssGetContStateAddress 10-27
ssGetContStates 10-28
ssGetDataTypeId 10-29
ssGetDataTypeName 10-30
ssGetDataTypeSize 10-31
ssGetDataTypeZero 10-32
ssGetDiscStates 10-33
ssGetDTypeIdFromMxArray 10-34
ssGetDWork 10-36
ssGetDWorkComplexSignal 10-37
ssGetDWorkDataType 10-38
ssGetDWorkName 10-39, 10-40, 10-41, 10-149,
10-150, 10-151
I-5
Index
I-6
ssGetDWorkRTWTypeQualifier 10-42
ssGetDWorkUsedAsDState 10-43
ssGetDWorkWidth 10-44
ssGetdX 10-45
ssGetErrorStatus 10-46
ssGetInlineParameters 10-47
ssGetInputPortBufferDstPort 10-48
ssGetInputPortComplexSignal 10-49
ssGetInputPortConnected 10-50
ssGetInputPortDataType 10-51
ssGetInputPortDimensions 10-52
ssGetInputPortDirectFeedThrough 10-53
ssGetInputPortFrameData 10-54
ssGetInputPortNumDimensions 10-55
ssGetInputPortOffsetTime 10-56
ssGetInputPortOverWritable 10-57
ssGetInputPortRealSignal 10-58
ssGetInputPortRealSignalPtrs 10-60
ssGetInputPortRequiredContiguous 10-61
ssGetInputPortReusable 10-62
ssGetInputPortSampleTime 10-63
ssGetInputPortSampleTimeIndex 10-64
ssGetInputPortSignal 10-65
ssGetInputPortSignalAddress 10-66
ssGetInputPortSignalPtrs 10-67
ssGetInputPortWidth 10-68
ssGetIWork 10-69
ssGetModelName 10-71
ssGetModeVector 10-72
ssGetModeVectorValue 10-13, 10-73
ssGetNonsampledZCs 10-74
ssGetNumContStates 10-75
ssGetNumDataTypes 10-76
ssGetNumDiscStates 10-77
ssGetNumDWork 10-78
ssGetNumInputPorts 10-79
ssGetNumIWork 10-80
ssGetNumModes 10-81
ssGetNumNonsampledZCs 10-82
ssGetNumOutputPorts 10-83
ssGetNumParameters 10-84
ssGetNumPWork 10-86
ssGetNumRunTimeParams 10-85
ssGetNumRWork 10-87
ssGetNumSampleTimes 10-88
ssGetNumSFcnParams 10-89
ssGetOutputPortBeingMerged 10-90
ssGetOutputPortComplexSignal 10-91
ssGetOutputPortDataType 10-92
ssGetOutputPortDimensions 10-93
ssGetOutputPortFrameData 10-94
ssGetOutputPortNumDimensions 10-95
ssGetOutputPortOffsetTime 10-96
ssGetOutputPortRealSignal 10-97
ssGetOutputPortReusable 10-98
ssGetOutputPortSampleTime 10-99
ssGetOutputPortSignal 10-100
ssGetOutputPortSignalAddress 10-101
ssGetOutputPortWidth 10-102
ssGetParentSS 10-103
ssGetPath 10-104
ssGetPlacementGroup 10-105
ssGetPWork 10-107
ssGetRealDiscStates 10-109
ssGetRootSS 10-110
ssGetRunTimeParamInfo 10-111
ssGetRWork 10-70, 10-108, 10-112, 10-113, 10-172,
10-206, 10-207
ssGetSampleTimeOffset 10-114
ssGetSampleTimePeriod 10-115
ssGetSFcnParam 10-116
ssGetSFcnParamsCount 10-117
ssGetSimMode 10-118
ssGetSolverMode 10-119
Index
ssGetSolverName 10-120
ssGetStateAbsTol 10-121
ssGetStopRequested 10-122
ssGetT 10-123
ssGetTaskTime 10-124
ssGetTFinal 10-125
ssGetTNext 10-126
ssGetTStart 10-127
ssGetUserData 10-128
ssIsContinuousTask 10-129
ssIsFirstInitCond 10-130
ssIsMajorTimeStep 10-131
ssIsMinorTimeStep 10-132
ssIsSampleHit 10-133
ssIsSpecialSampleHit 10-134
ssIsVariableStepSolver 10-135
ssParamRec structure 10-208
returned by ssGetRunTimeParamInfo 10-111
ssPrintf 10-136
ssRegAllTunableParamsAsRunTimeParams
10-138
ssRegisterDataType 10-139
ssSampleTimeAndOffsetAreTriggered 10-106,
10-140
ssSetBlockReduction 10-141
ssSetCallSystemOutput 10-142
ssSetDataTypeSize 10-143
ssSetDataTypeZero 10-144
ssSetDWorkComplexSignal 10-146
ssSetDWorkDataType 10-147
ssSetDWorkName 10-148
ssSetDWorkUsedAsDState 10-152
ssSetDWorkWidth 10-153
ssSetErrorStatus 10-154
ssSetExternalModeFcn 10-155
ssSetInputPortComplexSignal 10-156
ssSetInputPortDataType 10-157
ssSetInputPortDimensionInfo 10-158
ssSetInputPortDirectFeedThrough 10-160
ssSetInputPortFrameData 10-161
ssSetInputPortMatrixDimensions 10-162
ssSetInputPortOffsetTime 10-163
ssSetInputPortOverWritable 10-164
ssSetInputPortRequiredContiguous 10-165
ssSetInputPortReusable 10-166
ssSetInputPortSampleTime 10-168
ssSetInputPortSampleTimeIndex 10-169
ssSetInputPortVectorDimension 10-170
ssSetInputPortWidth 10-171
ssSetModeVectorValue 10-173
ssSetNumContStates 10-174
ssSetNumDiscStates 10-175
ssSetNumDWork 10-176
ssSetNumInputPorts 10-177
ssSetNumIWork 10-178
ssSetNumModes 10-179
ssSetNumNonsampledZCs 10-180
ssSetNumOutputPorts 10-181
ssSetNumPWork 10-182
ssSetNumRunTimeParams 10-183
ssSetNumRWork 10-184
ssSetNumSampleTimes 10-185
ssSetNumSFcnParams 10-186
ssSetOffsetTime 10-187
ssSetOptions 10-188
ssSetOutputPortComplexSignal 10-192
ssSetOutputPortDataType 10-193
ssSetOutputPortFrameData 10-195
ssSetOutputPortMatrixDimensions 10-196
ssSetOutputPortOffsetTime 10-197
ssSetOutputPortReusable 10-198
ssSetOutputPortSampleTime 10-200
ssSetOutputPortVectorDimension 10-201
ssSetOutputPortWidth 10-202
I-7
Index
I-8
ssSetParameterName 10-203
ssSetParameterTunable 10-204
ssSetPlacementGroup 10-205
ssSetRunTimeParamInfo 10-208
ssSetSampleTime 10-211
ssSetSFcnParamNotTunable 10-212
ssSetSFcnParamTunable 10-213
ssSetSolverNeedsReset 10-214
ssSetStopRequested 10-216
ssSetTNext 10-217
ssSetUserData 10-218
ssSetVectorMode 10-219
ssUpdateAllTunableParamsAsRunTimeParams
10-220
ssUpdateRunTimeParamData 10-221
ssUpdateRunTimeParamInfo 10-223
ssWarning 10-224
ssWriteRTW2dMatParam 10-225
ssWriteRTWMx2dMatParam 10-226
ssWriteRTWMxVectParam 10-227
ssWriteRTWParameters 10-228
ssWriteRTWParamSettings 10-232
ssWriteRTWScalarParam 10-236
ssWriteRTWStr 10-237
ssWriteRTWStrParam 10-238
ssWriteRTWStrVectParam 10-239
ssWriteRTWVectParam 10-240
ssWriteRTWWorkVect 10-241
synchronizing multirate S-Function blocks 7-24
T
templates
M-file S-function 2-2
time-varying continuous transfer function
example (C MEX) 7-64
tmwtypes.h 3-32
tunable parameters 7-3
V
variable-step S-function example (C MEX) 7-49
variable-step S-function example (M-file) 2-17
W
work vectors 7-26
wrapper S-functions 8-9
writing S-functions in Ada 5-3
writing S-functions in C++ 4-2
writing S-functions in MATLAB 2-2
Z
zero-crossing S-function example (C MEX) 7-52
| 课件名称： | 自动控制原理（双语教学） |
| 课件分类： | 电气与自动化 |
| 课件类型： | 电子教案 |
| 文件大小： | 46.6MB |
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- 1. 自动控制原理（双语教学）：01.Get started with Matlab
- 2. 自动控制原理（双语教学）：02.Matlab & system emluator
- 3. 自动控制原理（双语教学）：03.control toolbox
- 4. 自动控制原理（双语教学）：04.LMI Control Toolbox
- 5. 自动控制原理（双语教学）：05.simulink reference
- 6. 自动控制原理（双语教学）：06.creating GUI
- 7. 自动控制原理（双语教学）：07.Graphics
- 8. 自动控制原理（双语教学）：08.optimization toolbox
- 9. 自动控制原理（双语教学）：09.s function reference
- 10. 自动控制原理（双语教学）：10.S-function
- 11. 自动控制原理（双语教学）：11.MAT-file Format
- 12. 自动控制原理（双语教学）：12.ident
- 13. 自动控制原理（双语教学）：13.mpc simulink library
- 14. 自动控制原理（双语教学）：14.mpc
- 15. 自动控制原理（双语教学）：1.4.1
- 16. 自动控制原理（双语教学）：1.4.2
- 17. 自动控制原理（双语教学）：1.4.3
- 18. 自动控制原理（双语教学）：1.4.4
