Honored ContributorHi guys, I got a Fit warning like below: Warning (335093): TimeQuest Timing Analyzer is analyzing 45 combinational loops as latches. This warning is not very self-explanatory. There's no farther detail, even doesn't tell me which part of code caused this problem. How can I locate the root cause. Thanks in advance.
Honored ContributorThe warning is quite clear: you have designed combinatorial logic which somehow feeds itself with its own outputs.
This usually leads to a latch-like behavior. If you are not fully aware of the involved timings, you could have unpredictable results, race conditions, unstable outputs. That's why TQ warns you.Honored ContributorThanks, Cris.
I already knew the risk, so I must find them. The situation I got is that the RTL is not designed by myself, so it is not easy for me to review the RTL line by line to find the latch-like coding style. I am wondering if TQ can tell me more info besides just give out the number of combinatorial loop, such as: 1. which part of RTL code is causing the combinatorial loops. 2. if it can't locate the loops in RTL, maybe it can locate it in Net List or in Technology Map View. 3. some other ways help me to find the loops quickly. Theoretically, TQ knows there are 45 combinatorial loops in the design, it must know where they are, right? Thanks a lot.Honored ContributorTry reporting combinatorial loops information with:
check_timing -include loopsHonored ContributorGood call...
check_timing -include latches ...gave the me the information I needed when I came across this warning.
