UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 17707

9.1i PrimeTime - The Timing Analysis of FROM:TO constraint does not match in PrimeTime

Description

When I run the design through PrimeTime and Timing Analyzer, why do more paths appear in PrimeTime?

Solution

The Verbose Report of Minimum Paths indicates that race/hold analysis is no longer performed for MAXDELAY FROM:TO constraints. Because of this, the hold will not be checked for multicycle paths (slow or fast exception) and might be another potential area of discrepancy between TRCE/PrimeTime, as PrimeTime does check hold for this case.

This is definitely a discrepancy issue; however, two things should be noted: first, it is still possible to cover a multicycle path with a PERIOD constraint and perform a race/hold check; second, it is highly unlikely that a slow exception path will have a race/hold violation, as these paths usually require a longer amount of time to reach their destination.

Fast exceptions can be potential issues when comparing PrimeTime to TRCE. To obtain a fast exception to analyze, use one of the following suggestions:

- Xilinx recommends that TRCE users create FROM:TO constraints for the fast exceptions. If you want to perform a hold/race check on this path, create a PERIOD constraint instead of a FROM:TO constraint.

- Translate the resultant group constraints to SDC.

- Leave the MAX delays as FROM:TO constraints in translation to SDC and PrimeTime.

AR# 17707
Date Created 09/03/2007
Last Updated 01/18/2010
Status Archive
Type General Article