Programmable Devices
CPLDs, FPGAs, SoC FPGAs, Configuration, and Transceivers
20705 Discussions

Timing Contraint on latch

Altera_Forum
Honored Contributor II
1,627 Views

Anyone knows how to constraint the latch related circuitry? I attached a pdf that show the diagram. The clock is running at 10MHz and the timing requirements from input to output is 80nSec.

0 Kudos
3 Replies
Altera_Forum
Honored Contributor II
402 Views

What is the purpose of this latch? Generally, using latches is not good design practice.  

 

 

 

--- Quote Start ---  

Anyone knows how to constraint the latch related circuitry? I attached a pdf that show the diagram. The clock is running at 10MHz and the timing requirements from input to output is 80nSec. 

--- Quote End ---  

0 Kudos
Altera_Forum
Honored Contributor II
402 Views

I know using latch is not good design and do not want to use. Unfortunately, I must use it for my application. I need to find out how I can constraint these latch. I was thinking of using set_max_delay, but I'm not sure whether this would do it since set_max_delay is used for combinatorial logic path.

Altera_Forum
Honored Contributor II
402 Views

 

--- Quote Start ---  

I know using latch is not good design and do not want to use. Unfortunately, I must use it for my application. I need to find out how I can constraint these latch. I was thinking of using set_max_delay, but I'm not sure whether this would do it since set_max_delay is used for combinatorial logic path. 

--- Quote End ---  

 

Kattice, 

Yes, Latch IS a small combinational loop by itself. 

 

just interesting, why you cannot use the flip-flop with Synchronous Clear, because, anyway, you latch by implication depends on the Clock - it clears after 5 clock cycles. 

 

And for me it is looks strange to provide constraints for one specific module; what if you design contains 1000 logic gates, you cannot constraint each. 

0 Kudos
Reply