Copyright ? 1997 Altera Corporation
3/3/2011 P.1
Beginner VHDL
Training Class
Danny Mok
Altera HK FAE
(dmok@altera.com)
Copyright ? 1997 Altera Corporation
3/3/2011 P.2
What is VHDL
? Very high speed integrated Hardware Description
Language (VHDL)
– is an industry standard hardware description language
– description the hardware in language instead of graphic
? easy to modify
? easy to maintain
– very good for
? complex combinational logic
– BCD to 7 Segment converter
– address decoding
? state machine
? more than you want……..
Copyright ? 1997 Altera Corporation
3/3/2011 P.3
What VHDL Standard means
? The VHDL is used to describe
– Inputs port
– Outputs port
– behavior and functions of the circuits
? The language is defined by two successive standards
– IEEE Std 1076-1987 (called VHDL 1987)
– IEEE Std 1076-1993 (called VHDL 1993)
Inputs port
Output portfunctions
Copyright ? 1997 Altera Corporation
3/3/2011 P.4
Altera VHDL
? Altera Max+Plus II support both VHDL 1987 and
1993
? Max+Plus II only support SUBSET of the two IEEE
standard
? Detail of the support can be referred to Altera
Max+Plus II VHDL handbook on page 89 Section 3
Copyright ? 1997 Altera Corporation
3/3/2011 P.5
How to use the VHDL
? use any text editor to create the file
– Altera Software Max+Plus II provides text editor
click at
this icon
Copyright ? 1997 Altera Corporation
3/3/2011 P.6
? create your VHDL file
Copyright ? 1997 Altera Corporation
3/3/2011 P.7
? save your VHDL file as name.VHD
The name must be the same
Copyright ? 1997 Altera Corporation
3/3/2011 P.8
? Select the Standard Version of VHDL coding
– 1987 or 1993
Select which
version you
want
Copyright ? 1997 Altera Corporation
3/3/2011 P.9
? Compile your VHDL file
DONE !
Copyright ? 1997 Altera Corporation
3/3/2011 P.10
Bonus Topic
may help for
VHDL Design
within
Max+Plus II
Copyright ? 1997 Altera Corporation
3/3/2011 P.11
Turn on some Max+Plus II Option
? There are some built-in Option to assist the engineer
during the VHDL design stage
– Syntax Color Option from the Option menu
Turn on
this option
Reserve word in Blue
Copyright ? 1997 Altera Corporation
3/3/2011 P.12
User can modify the Color Option
? use the Color Palette under Option Menu to
customize the color of
– comments,illegal characters,megafunctions,
macrofuncitons….
Select
Element Select Color
Copyright ? 1997 Altera Corporation
3/3/2011 P.13
Error Location during Compilation
? Easy to locate the error
Click on
the error
message
Locate the error
Error location
Copyright ? 1997 Altera Corporation
3/3/2011 P.14
VHDL Template
I forgot …….
If-then-else
case-end case
loop-end loop
…
Modify the code as user want
Copyright ? 1997 Altera Corporation
3/3/2011 P.15
General VHDL Format
ENTITY test IS
PORT ( input_pin_name, IN bit;
output_pin_name, OUT bit);
END test;
ARCHITECTURE test_body OF test IS
BEGIN
output_pin_name <= input_pin_name;
END test_body;
Key Word
VHDL Format
Logic
This two must be the same
I/O port define
section
Logic Behaviour
define section
Must be the same
as the save TEST.VHD
file
Copyright ? 1997 Altera Corporation
3/3/2011 P.16
Your First VHDL design -- 2 input AND gate
Entity simand is
Port ( a,b, in bit;
c, out bit);
end simand;
architecture simand_body of simand is
begin
c <= a and b;
end simand_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.17
More detail
Copyright ? 1997 Altera Corporation
3/3/2011 P.18
Why I use VHDL instead of Graphic
? Easy to Modify
? It is more powerful than Graphic
? VHDL is a portable language because
– is device independent
– the same code can be applied to Device manufactured by
Company A or Company B
Copyright ? 1997 Altera Corporation
3/3/2011 P.19
? Graphic vs VHDL
– Graphic is what you draw is what you get
?, tell me what hardware you want and I will give it to you”
– VHDL is what you write is what functional you get
?, tell me how your circuit should behave and the VHDL
compiler will give you the hardware that does the job”
? but the designer can not control how the circuit implement
Copyright ? 1997 Altera Corporation
3/3/2011 P.20
Learning VHDL must learn
What is Combinatorial Logic
What is Sequential Logic
What is Concurrent Statement
What is Process Statement
Copyright ? 1997 Altera Corporation
3/3/2011 P.21
Combinatorial Logic
? Combinatorial Logic if
– Outputs at a specified time are a function only of the inputs at
that time
? e.g,decoders,multiplexers and adders
Output change
instantly when
input change
Copyright ? 1997 Altera Corporation
3/3/2011 P.22
Sequential Logic
? Sequential Logic if
– Outputs at a specified time are a function of the inputs at that time
and at all preceding times
– All sequential circuits must include one or more registers
? e.g,State Machine,Counters,Shift Register and Controllers
Outputs depends
on inputs and
previous output
Register is used to hold the previous value
Copyright ? 1997 Altera Corporation
3/3/2011 P.23
? Now everyone should know what is
– Combinational Logic
– Sequential Logic
Q, Then how about Concurrent or Process Statement?
What is it?
Copyright ? 1997 Altera Corporation
3/3/2011 P.24
Concurrent Statement
? All the Concurrent Statement is executed in parallel
? Concurrent Statement does not care the position within
the coding
? Concurrent Statement is, OUTPUT depends on INPUT
only
Entity test1 Is
Port ( a,b, in bit;
c,d, out bit);
end test1;
architecture test1_body of test1 is
begin
c <= a and b;
d <= a or b;
end test1_body;
Entity test1 Is
Port ( a,b, in bit;
c,d, out bit);
end test1;
architecture test1_body of test1 is
begin
d <= a or b;
c <= a and b;
end test1_body;
This two excute
in parallel
Does not care the position within the coding
Output depends on Input only
without any conditional
constraint
Copyright ? 1997 Altera Corporation
3/3/2011 P.25
THE SAME
C = A and B
D = A OR B
c <= a and b;
d <= a or b;
d <= a or b;
c <= a and b;
Copyright ? 1997 Altera Corporation
3/3/2011 P.26
Process Statement
? All the Process Statement is executed in parallel
? Within the Process Statement,the coding is execute in
sequential
? Process Statement is, OUTPUT depends on INPUT
with Sensitivity List to control the event happen
Copyright ? 1997 Altera Corporation
3/3/2011 P.27
Entity test1 is
Port ( clk,d1,d2, in bit;
q1,q2, out bit);
end test1;
architecture test1_body of test1 is
begin
Process (clk,d1)
begin
if (clk?event and clk = ?1?) then
q1 <= d1;
end if;
end process;
Process (clk,d2)
begin
if (clk?event and clk= ?1?) then
q2 <= d2;
end if;
end process;
end test1_body;
Entity test1 is
Port ( clk,d1,d2, in bit;
q1,q2, out bit);
end test1;
architecture test1_body of test1 is
begin
Process (clk,d2)
begin
if (clk?event and clk = ?1?) then
q2 <= d2;
end if;
end process;
Process (clk,d1)
begin
if (clk?event and clk= ?1?) then
q1 <= d1;
end if;
end process;
end test1_body;
This two processes
execute in parallel
The coding is execute
in sequential within
the process
The output depends
on input with
conditional constraint
Copyright ? 1997 Altera Corporation
3/3/2011 P.28
The two process statement execute in parallel
Copyright ? 1997 Altera Corporation
3/3/2011 P.29
? Now,I know what is
– combinational logic
– sequential logic
– concurrent statement
– process statement
Q, What is the usage of this in VHDL?
A, Engineer can use the mixture of
combinational logic,sequential logic,concurrent statement
and process statement
to do the design
Copyright ? 1997 Altera Corporation
3/3/2011 P.30
How to,.,?
? Now I know what is Combinational Logic but
Q, How to implement of Combinational Logic in VHDL?
? Combinational Logic can be implemented by
– Concurrent Signal Assigment Statements
– Process Statement that describe purely combinational behaviour i.e,
behaviour that does not depends on any CLOCK EDGE
Copyright ? 1997 Altera Corporation
3/3/2011 P.31
Concurrent Statements
for
Combinational Logic
Copyright ? 1997 Altera Corporation
3/3/2011 P.32
Concurrent Statements
? There are several different kinds of Concurrent
Statements
– (1) Simple Signal Assigments
– (2) Conditional Signal Assigments
– (3) Selected Signal Assigments
Copyright ? 1997 Altera Corporation
3/3/2011 P.33
(1) Simple Signal Assigment
? These kind of statements are executed in Parallel
Entity test1 is
port ( a,b,e, in bit;
c,d, out bit);
end test1;
architecture test1_body of test1 is
begin
c <= a and b;
d <= e;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.34
What kind of logic support
? AND
? NAND
? OR
? NOR
? XOR
? NOT
? more,......
Copyright ? 1997 Altera Corporation
3/3/2011 P.35
I want 5 Input AND Gate
Q,AND is only a two input,if I want more input,what can I do?
A, It is easy,we are due with Language not Graphic
Entity test1 is
port ( a,b,c,d,e, in bit;
f, out bit);
end test1;
architecture test1_body of test1 is
begin
f <= a and b and c and d and e;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.36
LAB 1
Design a 7 Input OR gate
Copyright ? 1997 Altera Corporation
3/3/2011 P.37
Sampling Coding
Entity test1 is
port ( a,b,c,d,e,f,g, in bit;
h, out bit);
end test1;
architecture test1_body of test1 is
begin
h <= a or b or c or d or e or f or g;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.38
(2) Conditional Signal Assigments
? The output get the value when the condition is true
– e.g,2 to 1 multiplexer
Entity test1 is
port (in1,in2,sel, in bit;
d, out bit);
end test1;
architecture test1_body of test1 is
begin
d <= in1 when sel = ?0?
else in2;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.39
If I want more -- 4 to 1 Mux
? Once again,you are due with Language not Graphic,so it is
easy
Entity test1 is
port (in1,in2,in3,in4, in bit;
sel1,sel2, in bit;
d, out bit);
end test1;
architecture test1_body of test1 is
begin
d <= in1 when sel1 = ?0? and sel2 = ?0? else
in2 when sel1 = ?0? and sel2 = ?1? else
in3 when sel1 = ?1? and sel2 = ?0? else
in4;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.40
(3) Select Signal Assignments
? The output get value when matching with the selected item
Entity test1 is
port (a,b,in bit;
sel, in bit;
c, out bit);
end test1;
architecture test1_body of test1 is
begin
with sel select
c <= a when ?1?,
b when ?0?;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.41
If I want more choice ---
? It is easy
Entity test1 is
port (in1,in2,in3,in4, in bit;
sel, in integer;
out1, out bit);
end test1;
architecture test1_body of test1 is
begin
with sel select
out1 <= in1 when 0,
in2 when 1,
in3 when 2,
in4 when 3;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.42
LAB 2
Convert the design from Graphic to VHDL
Copyright ? 1997 Altera Corporation
3/3/2011 P.43
Design Constraint
? Use the WHEN-ELSE statement to finish your design
100
010
001
other
Copyright ? 1997 Altera Corporation
3/3/2011 P.44
Sampling Coding
Entity test1 is
port (high,medium,low, in bit;
highest_level3,highest_level2, out bit;
highest_level1,highest_level0, out bit);
end test1;
architecture test1_body of test1 is
begin
highest_level3 <= ?1? when high=?1? and medium=?0? and low=?0? else
?0?;
highest_level2 <= ?1? when high=?0? and medium=?1? and low=?0? else
?0?;
highest_level1 <= ?1? when high=?0? and medium=?0? and low=?1? else
?0?;
highest_level0 <= ?0? when high=?1? and medium=?0? and low=?0? else
?0? when high=?0? and medium=?1? and low=?0? else
?0? when high=?0? and medium=?0? and low=?1? else
?1?;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.45
Simulation
Copyright ? 1997 Altera Corporation
3/3/2011 P.46
Process Statement
for
Combinational Logic
Copyright ? 1997 Altera Corporation
3/3/2011 P.47
Process Statement
? There are some rules for the Process Statement
usage
– any kind of Process Statement must have SENITIVITY LIST
? sensitivity list contains the signals that cause the process
statement to execute if their values change
– the statement within the Process Statement will be execute
STEP-BY-STEP
Q, What does it all means?
A, Follow me.......
Copyright ? 1997 Altera Corporation
3/3/2011 P.48
Template for Process Statement
Using the,SENSITIVITY LIST”
name, PROCESS (sensitivity_list)
begin
sequential statement #1
sequential statement #2
.......
sequential statement # N
END PROCESS name;
General format for a Process Statemtent
Process ( )
begin
..
end process
Sensitivity List
Sequential Statement
The sequential statement execute one by one and
follow the order,ie,finish the #1 then #2 then #3
name is optional
Copyright ? 1997 Altera Corporation
3/3/2011 P.49
Example will be more clear
Entity test1 is
port (a,b,sel1,sel2, in bit;
result, out bit);
end test1;
architecture test1_body of test1 is
begin
process (sel1,sel2,a,b)
begin
if (sel1 = ?1?) then
result <= a;
elsif (sel2 = ?1?) then
result <= b;
else
result <= ?0?;
end if;
end process;
end test1_body;
Result change if sel1,sel2,a or b change the value
Wait, I can do the same join with Concurrent Statement
Copyright ? 1997 Altera Corporation
3/3/2011 P.50
Entity test1 is
port (a,b,sel1,sel2, in bit;
result, out bit);
end test1;
architecture test1_body of test1 is
begin
result <= a when sel1 = ?1? else
b when sel2 = ?1? else
?0?;
end test1_body;
Entity test1 is
port (a,b,sel1,sel2, in bit;
result, out bit);
end test1;
architecture test1_body of test1 is
begin
process (sel1,sel2,a,b)
begin
if (sel1 = ?1?) then
result <= a;
elsif (sel2 = ?1?) then
result <= b;
else
result <= ?0?;
end if;
end process;
end test1_body;
Same function but different
way to do the coding
Concurrent Statement Process Statement
Copyright ? 1997 Altera Corporation
3/3/2011 P.51
Q, What is the different between Concurrent and
Process Statement
A, For this simple example,both Concurrent and
Process can do the same job,But some function
must use Process Statement to do
Copyright ? 1997 Altera Corporation
3/3/2011 P.52
How to,.,?
? Now I know what is Sequential Logic but
Q, How to implement of Sequential Logic in VHDL?
? Sequential Logic can be implemented by
– Process Statement describe the logic with some CLOCK signal
Copyright ? 1997 Altera Corporation
3/3/2011 P.53
Process Statement
for
Sequential Logic
Copyright ? 1997 Altera Corporation
3/3/2011 P.54
How to do the Latch
Entity test1 is
port (clk,d,reset, in bit;
q, out bit);
end test1;
architecture test1_body of test1 is
begin
process (clk,d,reset)
begin
if (reset = ?1?) then
q <= ?0?;
elsif (clk = ?1?) then
q <= d;
end if;
end process;
end test1_body;
Reset take
over the
control first
Clk take
the control
second
Within the process excute in
step-by-step
Copyright ? 1997 Altera Corporation
3/3/2011 P.55
This is a LATCH
Copyright ? 1997 Altera Corporation
3/3/2011 P.56
If I modify the code to...
Entity test1 is
port (clk,d,reset, in bit;
q, out bit);
end test1;
architecture test1_body of test1 is
begin
process (clk)
begin
if (reset = ?1?) then
q <= ?0?;
elsif (clk = ?1?) then
q <= d;
end if;
end process;
end test1_body;
Note, the result is totally different
What is it?
Copyright ? 1997 Altera Corporation
3/3/2011 P.57
I get a Flip-Flop not a LATCH
Copyright ? 1997 Altera Corporation
3/3/2011 P.58
Why I have a Flip-Flop not a Latch
? Latch with a Sensitivity list
process (clk,d,reset)
? Flip-Flop with a Sensitivity list
process(clk)
Q, What is the Sensitivity list use for?
A, The OUTPUT change when the Sensitivity list
change
Copyright ? 1997 Altera Corporation
3/3/2011 P.59
More Detail
? process (clk,d,reset)
– this say that the OUTPUT change when either clk,d or reset
change,if clk,d or reset not change,then maintain the output
– what kind of device will provide this function?
LATCH
Copyright ? 1997 Altera Corporation
3/3/2011 P.60
? process (clk)
– this say that OUTPUT change when CLK change,if clk does
not change,maintain the output
– what kind of device will provide this function?
Flip-Flop
Copyright ? 1997 Altera Corporation
3/3/2011 P.61
? Now you can see VHDL is very powerful,but if you
don’t know what you are doing,you may not get what
you want
– e.g,you want a latch but actually you get a Flip-Flop
Copyright ? 1997 Altera Corporation
3/3/2011 P.62
The other way of coding
LIBRARY IEEE;
USE IEEE.std_logic_1164.all;
ENTITY tdff IS
PORT(clk,d,in std_logic;
q, out std_logic);
END tdff;
ARCHITECTURE behaviour OF tdff IS
BEGIN
PROCESS
BEGIN
wait until clk = '1';
q <= d;
END PROCESS;
END behaviour;
Copyright ? 1997 Altera Corporation
3/3/2011 P.63
Compare IF-THEN-ELSE vs WATI UNTIL
LIBRARY IEEE;
USE IEEE.std_logic_1164.all;
ENTITY tdff IS
PORT(clk,d,in std_logic;
q, out std_logic);
END tdff;
architecture behaviour OF tdff IS
BEGIN
PROCESS
BEGIN
wait until clk = '1';
q <= d;
END PROCESS;
END behaviour;
Entity test1 is
port (clk,d, in bit;
q, out bit);
end test1;
architecture test1_body of test1 is
begin
process (clk)
begin
if (clk = ?1?) then
q <= d;
end if;
end process;
end test1_body;
Entity test1 is
port (clk,d, in bit;
q, out bit);
end test1;
architecture test1_body of test1 is
begin
process (clk,d)
begin
if (clk = ?1? and clk?event) then
q <= d;
end if;
end process;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.64
Review
? Concurrent Statement for
– combinational logic (without Flip-flop circuit)
? eg,decoder,multiplixer,multiplier,adder
? Process Statement for
– combinational logic (without Flip-Flop circuit)
– Sequential logic (with Flip-Flop circuit)
? e.g,State machine,counters,controller
Copyright ? 1997 Altera Corporation
3/3/2011 P.65
Copyright ? 1997 Altera Corporation
3/3/2011 P.66
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d, out bit);
END test1;
architecture test1_body of test1 is
begin
d <= ((a and b) xor c);
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.67
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e, out bit);
END test1;
architecture test1_body of test1 is
begin
process(a,b,c)
begin
d <= ((a and b) xor c);
e <= ((a or b) nand c);
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.68
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d, out bit);
END test1;
architecture test1_body of test1 is
begin
process(a,b,c)
begin
d <= ((a and b) xor c);
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.69
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e, out bit);
END test1;
architecture test1_body of test1 is
begin
process(a,b,c)
begin
d <= ((a and b) xor c);
e <= ((a or b) nand c);
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.70
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e, out bit);
END test1;
architecture test1_body of test1 is
begin
if (clk'event and clk='1') then
d <= ((a or b) and c);
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.71
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d, out bit);
END test1;
architecture test1_body of test1 is
begin
process(clk)
begin
if (clk'event and clk='1') then
d <= ((a or b) and c);
end if;
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.72
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e, out bit);
END test1;
architecture test1_body of test1 is
begin
process(clk,a,b,c)
begin
if (clk'event and clk='1') then
d <= ((a xor b) and c);
end if;
e <= ((a or b) nand c);
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.73
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e,f, out bit);
END test1;
architecture test1_body of test1 is
begin
process(clk,a,b,c)
begin
if (clk'event and clk='1') then
d <= ((a xor b) and c);
end if;
if (clk'event and clk='1') then
e <= ((a or b) nand c);
end if;
if (a = '1') then
f <= (a or b);
end if;
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.74
Seat down an think of your design
D e s i g n F l o w
C o n cu r r e n t
sta t e m e n t
or
P r o ce ss sta t e m e n t
P r o ce ss
sta t e m e n t
C o n c u r r e n t
+
P r o c e s s
s t a t e m e n t
D o e s t h e
d e s i g n i s a
p u r e
s e q u e n t i a l c i r c u i t
D o e s t h e
d e si g n i s a
p u r e
c o m b i n a t i o n a l c i r c u i t
Y N
Y N
Copyright ? 1997 Altera Corporation
3/3/2011 P.75
Compare of AHDL vs VHDL
Variable
temp, dff
temp.clk = clk;
temp.d = data
out = temp.out
if (clk?event and clk=?1?)then
out <= d;
end if;
AHDL VHDL
Both give me the DFF,and timing,functional
are all the same,there is no difference between!!!
Copyright ? 1997 Altera Corporation
3/3/2011 P.76
Closer look of the ADHL
Variable
temp, dff
temp.clk = clk;
temp.d = data
out = temp.out
I want a DFF and named it as,temp”
The DFF?s clock input pin is connected to,clk”
The DFF?s data input pin is connected to,data”
The DFF?s out output pin is connected to,out”
You want a DFF and tell the Max+Plus II how to connect all the input and output pin,
so Max+Plus II will follow your instruction and give you a DFF and connect all the pin
in order to give you what you want,You will get a DFF today,tomorrow or 1000 years later,
because you tell me you want a DFF
Copyright ? 1997 Altera Corporation
3/3/2011 P.77
Closer look at the VHDL
if (clk?event and clk=?1?)then
out <= d;
end if;
When there is a,clk” transaction and stable at,1”then perform
the following function,how to connect the pin,I don?t know!!!
I want the,out” equal to the,d”,but how to connect the pin,
I don?t know!!!!!!
So now,base on what the function you want,the VHDL compiler find out that a DFF will meet
your requirement,so it give you a DFF,Since the DFF is given to you by VHDL compiler,so you
may get a DFF today,but get a latch tomorrow,or get a JKFF 1000 years later -- because you just
tell me what is the function you want and how to implement it is really up to
the VHDL compiler,as far as VHDL give you the function you want is OK!!
Copyright ? 1997 Altera Corporation
3/3/2011 P.78
Conclusion of learning
? Learned what is Combinational Logic/Circuits
? Learned what is Sequential Logic/Circuits
? Understand the different between Concurrent
Statement and Process Statement
Copyright ? 1997 Altera Corporation
3/3/2011 P.79
? Understand the usage of the
– Concurrent Statement
? for Combinational Logic
– simple signal assignment statement
– conditional signal assignment statement
– selected signal assignement statement
– Process Statement
? for Combinational Logic
? for Sequential Logic
– if-then-else structure for Latch
– if-then-else structure for Flip-Flop
– wait until structure for Flip-Flop
Copyright ? 1997 Altera Corporation
3/3/2011 P.80
? All you learn is the basic concept of the VHDL
language
? This is the Beginner VHDL Training Class
? The detail of the Circuit design will be covered at the
Intermediate VHDL Training Class
? Advance VHDL language will be covered at the
Expert VHDL Training Class
Copyright ? 1997 Altera Corporation
3/3/2011 P.81
The most important thing of VHDL Language
,Tell me how your circuit should behave and the VHDL
compiler will give you the hardware circuit that does
the job”
? e.g,Latch and Flip-Flop is a good example
Copyright ? 1997 Altera Corporation
3/3/2011 P.82
VHDL
with
Graphic Interface
Copyright ? 1997 Altera Corporation
3/3/2011 P.83
I have some bug free Graphic designs,
Q, I have some bug free Graphic designs,how can I re-
use it with my new VHDL design file?
A, You can convert your Graphic design to VHDL
coding design manually,but
? it takes time
? human conversion error
OR
A, You can convert your new VHDL coding design to
Graphic and integrate with your old Graphic design
? it is fast and easy
? Max+Plus II handle the conversion,so no error guarantee
Copyright ? 1997 Altera Corporation
3/3/2011 P.84
Good but How
It is easy,just follow me
LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.std_logic_arith.all;
ENTITY adder IS
PORT (op1,op2, IN UNSIGNED(7 downto 0);
result, OUT INTEGER);
END adder;
ARCHITECTURE maxpld OF adder IS
BEGIN
result <= CONV_INTEGER(op1 + op2);
END maxpld;
Use it as normal Graphic Symbol
Copyright ? 1997 Altera Corporation
3/3/2011 P.85
See you at the Intermediate
VHDL training class
3/3/2011 P.1
Beginner VHDL
Training Class
Danny Mok
Altera HK FAE
(dmok@altera.com)
Copyright ? 1997 Altera Corporation
3/3/2011 P.2
What is VHDL
? Very high speed integrated Hardware Description
Language (VHDL)
– is an industry standard hardware description language
– description the hardware in language instead of graphic
? easy to modify
? easy to maintain
– very good for
? complex combinational logic
– BCD to 7 Segment converter
– address decoding
? state machine
? more than you want……..
Copyright ? 1997 Altera Corporation
3/3/2011 P.3
What VHDL Standard means
? The VHDL is used to describe
– Inputs port
– Outputs port
– behavior and functions of the circuits
? The language is defined by two successive standards
– IEEE Std 1076-1987 (called VHDL 1987)
– IEEE Std 1076-1993 (called VHDL 1993)
Inputs port
Output portfunctions
Copyright ? 1997 Altera Corporation
3/3/2011 P.4
Altera VHDL
? Altera Max+Plus II support both VHDL 1987 and
1993
? Max+Plus II only support SUBSET of the two IEEE
standard
? Detail of the support can be referred to Altera
Max+Plus II VHDL handbook on page 89 Section 3
Copyright ? 1997 Altera Corporation
3/3/2011 P.5
How to use the VHDL
? use any text editor to create the file
– Altera Software Max+Plus II provides text editor
click at
this icon
Copyright ? 1997 Altera Corporation
3/3/2011 P.6
? create your VHDL file
Copyright ? 1997 Altera Corporation
3/3/2011 P.7
? save your VHDL file as name.VHD
The name must be the same
Copyright ? 1997 Altera Corporation
3/3/2011 P.8
? Select the Standard Version of VHDL coding
– 1987 or 1993
Select which
version you
want
Copyright ? 1997 Altera Corporation
3/3/2011 P.9
? Compile your VHDL file
DONE !
Copyright ? 1997 Altera Corporation
3/3/2011 P.10
Bonus Topic
may help for
VHDL Design
within
Max+Plus II
Copyright ? 1997 Altera Corporation
3/3/2011 P.11
Turn on some Max+Plus II Option
? There are some built-in Option to assist the engineer
during the VHDL design stage
– Syntax Color Option from the Option menu
Turn on
this option
Reserve word in Blue
Copyright ? 1997 Altera Corporation
3/3/2011 P.12
User can modify the Color Option
? use the Color Palette under Option Menu to
customize the color of
– comments,illegal characters,megafunctions,
macrofuncitons….
Select
Element Select Color
Copyright ? 1997 Altera Corporation
3/3/2011 P.13
Error Location during Compilation
? Easy to locate the error
Click on
the error
message
Locate the error
Error location
Copyright ? 1997 Altera Corporation
3/3/2011 P.14
VHDL Template
I forgot …….
If-then-else
case-end case
loop-end loop
…
Modify the code as user want
Copyright ? 1997 Altera Corporation
3/3/2011 P.15
General VHDL Format
ENTITY test IS
PORT ( input_pin_name, IN bit;
output_pin_name, OUT bit);
END test;
ARCHITECTURE test_body OF test IS
BEGIN
output_pin_name <= input_pin_name;
END test_body;
Key Word
VHDL Format
Logic
This two must be the same
I/O port define
section
Logic Behaviour
define section
Must be the same
as the save TEST.VHD
file
Copyright ? 1997 Altera Corporation
3/3/2011 P.16
Your First VHDL design -- 2 input AND gate
Entity simand is
Port ( a,b, in bit;
c, out bit);
end simand;
architecture simand_body of simand is
begin
c <= a and b;
end simand_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.17
More detail
Copyright ? 1997 Altera Corporation
3/3/2011 P.18
Why I use VHDL instead of Graphic
? Easy to Modify
? It is more powerful than Graphic
? VHDL is a portable language because
– is device independent
– the same code can be applied to Device manufactured by
Company A or Company B
Copyright ? 1997 Altera Corporation
3/3/2011 P.19
? Graphic vs VHDL
– Graphic is what you draw is what you get
?, tell me what hardware you want and I will give it to you”
– VHDL is what you write is what functional you get
?, tell me how your circuit should behave and the VHDL
compiler will give you the hardware that does the job”
? but the designer can not control how the circuit implement
Copyright ? 1997 Altera Corporation
3/3/2011 P.20
Learning VHDL must learn
What is Combinatorial Logic
What is Sequential Logic
What is Concurrent Statement
What is Process Statement
Copyright ? 1997 Altera Corporation
3/3/2011 P.21
Combinatorial Logic
? Combinatorial Logic if
– Outputs at a specified time are a function only of the inputs at
that time
? e.g,decoders,multiplexers and adders
Output change
instantly when
input change
Copyright ? 1997 Altera Corporation
3/3/2011 P.22
Sequential Logic
? Sequential Logic if
– Outputs at a specified time are a function of the inputs at that time
and at all preceding times
– All sequential circuits must include one or more registers
? e.g,State Machine,Counters,Shift Register and Controllers
Outputs depends
on inputs and
previous output
Register is used to hold the previous value
Copyright ? 1997 Altera Corporation
3/3/2011 P.23
? Now everyone should know what is
– Combinational Logic
– Sequential Logic
Q, Then how about Concurrent or Process Statement?
What is it?
Copyright ? 1997 Altera Corporation
3/3/2011 P.24
Concurrent Statement
? All the Concurrent Statement is executed in parallel
? Concurrent Statement does not care the position within
the coding
? Concurrent Statement is, OUTPUT depends on INPUT
only
Entity test1 Is
Port ( a,b, in bit;
c,d, out bit);
end test1;
architecture test1_body of test1 is
begin
c <= a and b;
d <= a or b;
end test1_body;
Entity test1 Is
Port ( a,b, in bit;
c,d, out bit);
end test1;
architecture test1_body of test1 is
begin
d <= a or b;
c <= a and b;
end test1_body;
This two excute
in parallel
Does not care the position within the coding
Output depends on Input only
without any conditional
constraint
Copyright ? 1997 Altera Corporation
3/3/2011 P.25
THE SAME
C = A and B
D = A OR B
c <= a and b;
d <= a or b;
d <= a or b;
c <= a and b;
Copyright ? 1997 Altera Corporation
3/3/2011 P.26
Process Statement
? All the Process Statement is executed in parallel
? Within the Process Statement,the coding is execute in
sequential
? Process Statement is, OUTPUT depends on INPUT
with Sensitivity List to control the event happen
Copyright ? 1997 Altera Corporation
3/3/2011 P.27
Entity test1 is
Port ( clk,d1,d2, in bit;
q1,q2, out bit);
end test1;
architecture test1_body of test1 is
begin
Process (clk,d1)
begin
if (clk?event and clk = ?1?) then
q1 <= d1;
end if;
end process;
Process (clk,d2)
begin
if (clk?event and clk= ?1?) then
q2 <= d2;
end if;
end process;
end test1_body;
Entity test1 is
Port ( clk,d1,d2, in bit;
q1,q2, out bit);
end test1;
architecture test1_body of test1 is
begin
Process (clk,d2)
begin
if (clk?event and clk = ?1?) then
q2 <= d2;
end if;
end process;
Process (clk,d1)
begin
if (clk?event and clk= ?1?) then
q1 <= d1;
end if;
end process;
end test1_body;
This two processes
execute in parallel
The coding is execute
in sequential within
the process
The output depends
on input with
conditional constraint
Copyright ? 1997 Altera Corporation
3/3/2011 P.28
The two process statement execute in parallel
Copyright ? 1997 Altera Corporation
3/3/2011 P.29
? Now,I know what is
– combinational logic
– sequential logic
– concurrent statement
– process statement
Q, What is the usage of this in VHDL?
A, Engineer can use the mixture of
combinational logic,sequential logic,concurrent statement
and process statement
to do the design
Copyright ? 1997 Altera Corporation
3/3/2011 P.30
How to,.,?
? Now I know what is Combinational Logic but
Q, How to implement of Combinational Logic in VHDL?
? Combinational Logic can be implemented by
– Concurrent Signal Assigment Statements
– Process Statement that describe purely combinational behaviour i.e,
behaviour that does not depends on any CLOCK EDGE
Copyright ? 1997 Altera Corporation
3/3/2011 P.31
Concurrent Statements
for
Combinational Logic
Copyright ? 1997 Altera Corporation
3/3/2011 P.32
Concurrent Statements
? There are several different kinds of Concurrent
Statements
– (1) Simple Signal Assigments
– (2) Conditional Signal Assigments
– (3) Selected Signal Assigments
Copyright ? 1997 Altera Corporation
3/3/2011 P.33
(1) Simple Signal Assigment
? These kind of statements are executed in Parallel
Entity test1 is
port ( a,b,e, in bit;
c,d, out bit);
end test1;
architecture test1_body of test1 is
begin
c <= a and b;
d <= e;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.34
What kind of logic support
? AND
? NAND
? OR
? NOR
? XOR
? NOT
? more,......
Copyright ? 1997 Altera Corporation
3/3/2011 P.35
I want 5 Input AND Gate
Q,AND is only a two input,if I want more input,what can I do?
A, It is easy,we are due with Language not Graphic
Entity test1 is
port ( a,b,c,d,e, in bit;
f, out bit);
end test1;
architecture test1_body of test1 is
begin
f <= a and b and c and d and e;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.36
LAB 1
Design a 7 Input OR gate
Copyright ? 1997 Altera Corporation
3/3/2011 P.37
Sampling Coding
Entity test1 is
port ( a,b,c,d,e,f,g, in bit;
h, out bit);
end test1;
architecture test1_body of test1 is
begin
h <= a or b or c or d or e or f or g;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.38
(2) Conditional Signal Assigments
? The output get the value when the condition is true
– e.g,2 to 1 multiplexer
Entity test1 is
port (in1,in2,sel, in bit;
d, out bit);
end test1;
architecture test1_body of test1 is
begin
d <= in1 when sel = ?0?
else in2;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.39
If I want more -- 4 to 1 Mux
? Once again,you are due with Language not Graphic,so it is
easy
Entity test1 is
port (in1,in2,in3,in4, in bit;
sel1,sel2, in bit;
d, out bit);
end test1;
architecture test1_body of test1 is
begin
d <= in1 when sel1 = ?0? and sel2 = ?0? else
in2 when sel1 = ?0? and sel2 = ?1? else
in3 when sel1 = ?1? and sel2 = ?0? else
in4;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.40
(3) Select Signal Assignments
? The output get value when matching with the selected item
Entity test1 is
port (a,b,in bit;
sel, in bit;
c, out bit);
end test1;
architecture test1_body of test1 is
begin
with sel select
c <= a when ?1?,
b when ?0?;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.41
If I want more choice ---
? It is easy
Entity test1 is
port (in1,in2,in3,in4, in bit;
sel, in integer;
out1, out bit);
end test1;
architecture test1_body of test1 is
begin
with sel select
out1 <= in1 when 0,
in2 when 1,
in3 when 2,
in4 when 3;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.42
LAB 2
Convert the design from Graphic to VHDL
Copyright ? 1997 Altera Corporation
3/3/2011 P.43
Design Constraint
? Use the WHEN-ELSE statement to finish your design
100
010
001
other
Copyright ? 1997 Altera Corporation
3/3/2011 P.44
Sampling Coding
Entity test1 is
port (high,medium,low, in bit;
highest_level3,highest_level2, out bit;
highest_level1,highest_level0, out bit);
end test1;
architecture test1_body of test1 is
begin
highest_level3 <= ?1? when high=?1? and medium=?0? and low=?0? else
?0?;
highest_level2 <= ?1? when high=?0? and medium=?1? and low=?0? else
?0?;
highest_level1 <= ?1? when high=?0? and medium=?0? and low=?1? else
?0?;
highest_level0 <= ?0? when high=?1? and medium=?0? and low=?0? else
?0? when high=?0? and medium=?1? and low=?0? else
?0? when high=?0? and medium=?0? and low=?1? else
?1?;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.45
Simulation
Copyright ? 1997 Altera Corporation
3/3/2011 P.46
Process Statement
for
Combinational Logic
Copyright ? 1997 Altera Corporation
3/3/2011 P.47
Process Statement
? There are some rules for the Process Statement
usage
– any kind of Process Statement must have SENITIVITY LIST
? sensitivity list contains the signals that cause the process
statement to execute if their values change
– the statement within the Process Statement will be execute
STEP-BY-STEP
Q, What does it all means?
A, Follow me.......
Copyright ? 1997 Altera Corporation
3/3/2011 P.48
Template for Process Statement
Using the,SENSITIVITY LIST”
name, PROCESS (sensitivity_list)
begin
sequential statement #1
sequential statement #2
.......
sequential statement # N
END PROCESS name;
General format for a Process Statemtent
Process ( )
begin
..
end process
Sensitivity List
Sequential Statement
The sequential statement execute one by one and
follow the order,ie,finish the #1 then #2 then #3
name is optional
Copyright ? 1997 Altera Corporation
3/3/2011 P.49
Example will be more clear
Entity test1 is
port (a,b,sel1,sel2, in bit;
result, out bit);
end test1;
architecture test1_body of test1 is
begin
process (sel1,sel2,a,b)
begin
if (sel1 = ?1?) then
result <= a;
elsif (sel2 = ?1?) then
result <= b;
else
result <= ?0?;
end if;
end process;
end test1_body;
Result change if sel1,sel2,a or b change the value
Wait, I can do the same join with Concurrent Statement
Copyright ? 1997 Altera Corporation
3/3/2011 P.50
Entity test1 is
port (a,b,sel1,sel2, in bit;
result, out bit);
end test1;
architecture test1_body of test1 is
begin
result <= a when sel1 = ?1? else
b when sel2 = ?1? else
?0?;
end test1_body;
Entity test1 is
port (a,b,sel1,sel2, in bit;
result, out bit);
end test1;
architecture test1_body of test1 is
begin
process (sel1,sel2,a,b)
begin
if (sel1 = ?1?) then
result <= a;
elsif (sel2 = ?1?) then
result <= b;
else
result <= ?0?;
end if;
end process;
end test1_body;
Same function but different
way to do the coding
Concurrent Statement Process Statement
Copyright ? 1997 Altera Corporation
3/3/2011 P.51
Q, What is the different between Concurrent and
Process Statement
A, For this simple example,both Concurrent and
Process can do the same job,But some function
must use Process Statement to do
Copyright ? 1997 Altera Corporation
3/3/2011 P.52
How to,.,?
? Now I know what is Sequential Logic but
Q, How to implement of Sequential Logic in VHDL?
? Sequential Logic can be implemented by
– Process Statement describe the logic with some CLOCK signal
Copyright ? 1997 Altera Corporation
3/3/2011 P.53
Process Statement
for
Sequential Logic
Copyright ? 1997 Altera Corporation
3/3/2011 P.54
How to do the Latch
Entity test1 is
port (clk,d,reset, in bit;
q, out bit);
end test1;
architecture test1_body of test1 is
begin
process (clk,d,reset)
begin
if (reset = ?1?) then
q <= ?0?;
elsif (clk = ?1?) then
q <= d;
end if;
end process;
end test1_body;
Reset take
over the
control first
Clk take
the control
second
Within the process excute in
step-by-step
Copyright ? 1997 Altera Corporation
3/3/2011 P.55
This is a LATCH
Copyright ? 1997 Altera Corporation
3/3/2011 P.56
If I modify the code to...
Entity test1 is
port (clk,d,reset, in bit;
q, out bit);
end test1;
architecture test1_body of test1 is
begin
process (clk)
begin
if (reset = ?1?) then
q <= ?0?;
elsif (clk = ?1?) then
q <= d;
end if;
end process;
end test1_body;
Note, the result is totally different
What is it?
Copyright ? 1997 Altera Corporation
3/3/2011 P.57
I get a Flip-Flop not a LATCH
Copyright ? 1997 Altera Corporation
3/3/2011 P.58
Why I have a Flip-Flop not a Latch
? Latch with a Sensitivity list
process (clk,d,reset)
? Flip-Flop with a Sensitivity list
process(clk)
Q, What is the Sensitivity list use for?
A, The OUTPUT change when the Sensitivity list
change
Copyright ? 1997 Altera Corporation
3/3/2011 P.59
More Detail
? process (clk,d,reset)
– this say that the OUTPUT change when either clk,d or reset
change,if clk,d or reset not change,then maintain the output
– what kind of device will provide this function?
LATCH
Copyright ? 1997 Altera Corporation
3/3/2011 P.60
? process (clk)
– this say that OUTPUT change when CLK change,if clk does
not change,maintain the output
– what kind of device will provide this function?
Flip-Flop
Copyright ? 1997 Altera Corporation
3/3/2011 P.61
? Now you can see VHDL is very powerful,but if you
don’t know what you are doing,you may not get what
you want
– e.g,you want a latch but actually you get a Flip-Flop
Copyright ? 1997 Altera Corporation
3/3/2011 P.62
The other way of coding
LIBRARY IEEE;
USE IEEE.std_logic_1164.all;
ENTITY tdff IS
PORT(clk,d,in std_logic;
q, out std_logic);
END tdff;
ARCHITECTURE behaviour OF tdff IS
BEGIN
PROCESS
BEGIN
wait until clk = '1';
q <= d;
END PROCESS;
END behaviour;
Copyright ? 1997 Altera Corporation
3/3/2011 P.63
Compare IF-THEN-ELSE vs WATI UNTIL
LIBRARY IEEE;
USE IEEE.std_logic_1164.all;
ENTITY tdff IS
PORT(clk,d,in std_logic;
q, out std_logic);
END tdff;
architecture behaviour OF tdff IS
BEGIN
PROCESS
BEGIN
wait until clk = '1';
q <= d;
END PROCESS;
END behaviour;
Entity test1 is
port (clk,d, in bit;
q, out bit);
end test1;
architecture test1_body of test1 is
begin
process (clk)
begin
if (clk = ?1?) then
q <= d;
end if;
end process;
end test1_body;
Entity test1 is
port (clk,d, in bit;
q, out bit);
end test1;
architecture test1_body of test1 is
begin
process (clk,d)
begin
if (clk = ?1? and clk?event) then
q <= d;
end if;
end process;
end test1_body;
Copyright ? 1997 Altera Corporation
3/3/2011 P.64
Review
? Concurrent Statement for
– combinational logic (without Flip-flop circuit)
? eg,decoder,multiplixer,multiplier,adder
? Process Statement for
– combinational logic (without Flip-Flop circuit)
– Sequential logic (with Flip-Flop circuit)
? e.g,State machine,counters,controller
Copyright ? 1997 Altera Corporation
3/3/2011 P.65
Copyright ? 1997 Altera Corporation
3/3/2011 P.66
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d, out bit);
END test1;
architecture test1_body of test1 is
begin
d <= ((a and b) xor c);
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.67
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e, out bit);
END test1;
architecture test1_body of test1 is
begin
process(a,b,c)
begin
d <= ((a and b) xor c);
e <= ((a or b) nand c);
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.68
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d, out bit);
END test1;
architecture test1_body of test1 is
begin
process(a,b,c)
begin
d <= ((a and b) xor c);
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.69
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e, out bit);
END test1;
architecture test1_body of test1 is
begin
process(a,b,c)
begin
d <= ((a and b) xor c);
e <= ((a or b) nand c);
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.70
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e, out bit);
END test1;
architecture test1_body of test1 is
begin
if (clk'event and clk='1') then
d <= ((a or b) and c);
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.71
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d, out bit);
END test1;
architecture test1_body of test1 is
begin
process(clk)
begin
if (clk'event and clk='1') then
d <= ((a or b) and c);
end if;
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.72
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e, out bit);
END test1;
architecture test1_body of test1 is
begin
process(clk,a,b,c)
begin
if (clk'event and clk='1') then
d <= ((a xor b) and c);
end if;
e <= ((a or b) nand c);
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.73
ENTITY test1 IS
PORT( clk,a,b,c, in bit;
d,e,f, out bit);
END test1;
architecture test1_body of test1 is
begin
process(clk,a,b,c)
begin
if (clk'event and clk='1') then
d <= ((a xor b) and c);
end if;
if (clk'event and clk='1') then
e <= ((a or b) nand c);
end if;
if (a = '1') then
f <= (a or b);
end if;
end process;
end test1_body;
Is this OK
Copyright ? 1997 Altera Corporation
3/3/2011 P.74
Seat down an think of your design
D e s i g n F l o w
C o n cu r r e n t
sta t e m e n t
or
P r o ce ss sta t e m e n t
P r o ce ss
sta t e m e n t
C o n c u r r e n t
+
P r o c e s s
s t a t e m e n t
D o e s t h e
d e s i g n i s a
p u r e
s e q u e n t i a l c i r c u i t
D o e s t h e
d e si g n i s a
p u r e
c o m b i n a t i o n a l c i r c u i t
Y N
Y N
Copyright ? 1997 Altera Corporation
3/3/2011 P.75
Compare of AHDL vs VHDL
Variable
temp, dff
temp.clk = clk;
temp.d = data
out = temp.out
if (clk?event and clk=?1?)then
out <= d;
end if;
AHDL VHDL
Both give me the DFF,and timing,functional
are all the same,there is no difference between!!!
Copyright ? 1997 Altera Corporation
3/3/2011 P.76
Closer look of the ADHL
Variable
temp, dff
temp.clk = clk;
temp.d = data
out = temp.out
I want a DFF and named it as,temp”
The DFF?s clock input pin is connected to,clk”
The DFF?s data input pin is connected to,data”
The DFF?s out output pin is connected to,out”
You want a DFF and tell the Max+Plus II how to connect all the input and output pin,
so Max+Plus II will follow your instruction and give you a DFF and connect all the pin
in order to give you what you want,You will get a DFF today,tomorrow or 1000 years later,
because you tell me you want a DFF
Copyright ? 1997 Altera Corporation
3/3/2011 P.77
Closer look at the VHDL
if (clk?event and clk=?1?)then
out <= d;
end if;
When there is a,clk” transaction and stable at,1”then perform
the following function,how to connect the pin,I don?t know!!!
I want the,out” equal to the,d”,but how to connect the pin,
I don?t know!!!!!!
So now,base on what the function you want,the VHDL compiler find out that a DFF will meet
your requirement,so it give you a DFF,Since the DFF is given to you by VHDL compiler,so you
may get a DFF today,but get a latch tomorrow,or get a JKFF 1000 years later -- because you just
tell me what is the function you want and how to implement it is really up to
the VHDL compiler,as far as VHDL give you the function you want is OK!!
Copyright ? 1997 Altera Corporation
3/3/2011 P.78
Conclusion of learning
? Learned what is Combinational Logic/Circuits
? Learned what is Sequential Logic/Circuits
? Understand the different between Concurrent
Statement and Process Statement
Copyright ? 1997 Altera Corporation
3/3/2011 P.79
? Understand the usage of the
– Concurrent Statement
? for Combinational Logic
– simple signal assignment statement
– conditional signal assignment statement
– selected signal assignement statement
– Process Statement
? for Combinational Logic
? for Sequential Logic
– if-then-else structure for Latch
– if-then-else structure for Flip-Flop
– wait until structure for Flip-Flop
Copyright ? 1997 Altera Corporation
3/3/2011 P.80
? All you learn is the basic concept of the VHDL
language
? This is the Beginner VHDL Training Class
? The detail of the Circuit design will be covered at the
Intermediate VHDL Training Class
? Advance VHDL language will be covered at the
Expert VHDL Training Class
Copyright ? 1997 Altera Corporation
3/3/2011 P.81
The most important thing of VHDL Language
,Tell me how your circuit should behave and the VHDL
compiler will give you the hardware circuit that does
the job”
? e.g,Latch and Flip-Flop is a good example
Copyright ? 1997 Altera Corporation
3/3/2011 P.82
VHDL
with
Graphic Interface
Copyright ? 1997 Altera Corporation
3/3/2011 P.83
I have some bug free Graphic designs,
Q, I have some bug free Graphic designs,how can I re-
use it with my new VHDL design file?
A, You can convert your Graphic design to VHDL
coding design manually,but
? it takes time
? human conversion error
OR
A, You can convert your new VHDL coding design to
Graphic and integrate with your old Graphic design
? it is fast and easy
? Max+Plus II handle the conversion,so no error guarantee
Copyright ? 1997 Altera Corporation
3/3/2011 P.84
Good but How
It is easy,just follow me
LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.std_logic_arith.all;
ENTITY adder IS
PORT (op1,op2, IN UNSIGNED(7 downto 0);
result, OUT INTEGER);
END adder;
ARCHITECTURE maxpld OF adder IS
BEGIN
result <= CONV_INTEGER(op1 + op2);
END maxpld;
Use it as normal Graphic Symbol
Copyright ? 1997 Altera Corporation
3/3/2011 P.85
See you at the Intermediate
VHDL training class
