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AR# 11766

9.1i PrimeTime/Timing Analyzer/Virtex-II/Virtex-II Pro - Timing Analyzer and PrimeTime report different OFFSET slacks for two-phase clocks

Description

For OFFSETs with both positive and negative edge flip-flops, TRCE incorrectly calculates slack for negative-edge flip-flops. This causes problems with the correlation of Trace and PrimeTime simulations.

Solution

TRACE calculates offset slacks for two-phase clocks by basing the calculation on the respective edges. PrimeTime, on the other hand, bases its slack calculation on only the rising clock edge for both positive- and negative-edge flops.

To remedy this issue, create a group and OFFSET it for the positive set of flip-flops; create another group and OFFSET it for the negative-edge flip-flops.

This issue will be fixed in the next major software release.

AR# 11766
Date Created 08/29/2007
Last Updated 01/18/2010
Status Archive
Type General Article