How did you find multi cycle path?

[u24c02]

Hi.
I have some question.
if you did synthesis without any information from digital designer's, How did you handle of SDC file on synthesis about multi cycle path ?

If you don't mind, Please let me know your experience and idea.

 

[sharath666]

It the responsibility of the designer to communicate it to the synthesis engineer if there are any multicycle paths in the design. The designer is the only person familiar with the design. The synthesis engineer is unaware of the design details.
Once the synthesis engineer is aware of multicycle paths, he can form the necessary constraints and use them in his SDC/constraints file.

 

[u24c02]

What if designer don't recognize their fault? Even you can't get any help then What do you do?

 

[sharath666]

As designs usually go through multiple rounds of review before signoff, it is highly uncommon for the designers to miss out on anything. In case you are a synthesis engineer try approaching the design team and confirm with them.
I am not sure how can a synthesis guy make out if a multicycle path constraint has been missed out at any place in the design. I guess finding a very long timing path is one clue. But not aware of any other clues. I would appreciate if others also chip in with their comments as "other clues" is something i also would like to know.

 

[ads-ee]

What if designer don't recognize their fault? Even you can't get any help then What do you do?

Are you saying you've found a timing fault in a path and don't know what to do?

If so, send an email back to the design group with details about all the failing source/destinations and tell them they don't meet timing and they need to change the RTL as they have too many levels of logic. As the synthesis engineer you should never assume that you have to add a multi-cycle path or one even exists in a design unless specifically told there is one. If the design team has multi-cycle paths but doesn't tell you about them, that is a different problem (i.e. You have a lax/poor design team).