Copyright ? 1997 Altera Corporation
3/3/2011 P.1
Tri-State vs MUX
Danny Mok
Altera HK FAE
(dmok@altera.com)
Copyright ? 1997 Altera Corporation
3/3/2011 P.2
Tri-State Buffer
? There are two application area for the Tri-State Buffer
– Internal Tri-State Buffer Logic
? need a Tri-State Buffer within Device
– External Tri-State Buffer Logic
? need a Tri-State Buffer at the I/O pin
? What Altera can provide
– Altera will implement Internal Tri-State Buffer with MUX
– All the I/O pad can provide a real Tri-State Buffer
? But some other PLD vendor can provide
– Internal Tri-State Buffer
? Is that any design limitation if use Altera Device?
Copyright ? 1997 Altera Corporation
3/3/2011 P.3
External Tri-State Buffer
This Tri-State Buffer for I/O pad application
Copyright ? 1997 Altera Corporation
3/3/2011 P.4
What Altera Provide for,...
All Altera Device will provide real Tri-State Buffer at the I/O pad
Copyright ? 1997 Altera Corporation
3/3/2011 P.5
Compilation Output
Copyright ? 1997 Altera Corporation
3/3/2011 P.6
Internal Tri-State Buffer
Internal Tri-State Buffer Logic
Copyright ? 1997 Altera Corporation
3/3/2011 P.7
What Altera Provide....
Altera Max+Plus II will convert Internal Tri-State Buffer
to MUX
Copyright ? 1997 Altera Corporation
3/3/2011 P.8
Can Altera support the following Design?
Copyright ? 1997 Altera Corporation
3/3/2011 P.9
Let us see,..
Use see,Altera can not handle this design,but the other PLD vendor X...,can
do it,Altera is not Good !!!!!!!!!!
Copyright ? 1997 Altera Corporation
3/3/2011 P.10
Look at the Circuit
Copyright ? 1997 Altera Corporation
3/3/2011 P.11
What the engineer wants?
X?
If there is an Internal Tri-State,what does the engineer
expect for the Output? The circuit itself is meaningless
Copyright ? 1997 Altera Corporation
3/3/2011 P.12
What is the application for
? Even though some PLD vendor can provide you the
Internal Tri-State Buffer
– but what is the applicaton for?
Copyright ? 1997 Altera Corporation
3/3/2011 P.13
Can Altera support this?
Before consider whether Altera support it or not? First ask is this a meaningful circuit
Yes,this is meaningful circuit
Altera support all kind of meaningful circuit
Copyright ? 1997 Altera Corporation
3/3/2011 P.14
Compilation Output
No doubt about it,Altera of course this because it is meaningful design
Copyright ? 1997 Altera Corporation
3/3/2011 P.15
Anything Wrong
This is my existing design and
work perfectly OK,but now I want
to use Altera device to implement it.
Is that OK !?!?!?
Copyright ? 1997 Altera Corporation
3/3/2011 P.16
Try it,...
Copyright ? 1997 Altera Corporation
3/3/2011 P.17
Correct Approach
WHY?
Copyright ? 1997 Altera Corporation
3/3/2011 P.18
Closer Look
Copyright ? 1997 Altera Corporation
3/3/2011 P.19
Max+Plus II Compilation Result
Copyright ? 1997 Altera Corporation
3/3/2011 P.20
Conclusion
? Altera provide complete solution for Tri-State Buffer
Design
– Internal Tri-State Buffer
? Altera Max+Plus II will convert Internal Tri-State Buffer to
MUX
? MUX solution provide more advantage then real Tri-State
Buffer
– no signal contention
– smaller in die size -> low device cost
– External Tri-State Buffer
? All Altera Device I/O pad provide a real Tri-State Buffer
Copyright ? 1997 Altera Corporation
3/3/2011 P.21
? A lot of Design need a real Tri-State Buffer at I/O
– almost all the PLD vendor provide this solution,of course
ALTERA does
? Some PLD vendor emphasize support Internal Tri-
State Buffer
– there is no meaningful application for this