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AR# 35886

14.x Timing - Unconstrained cross-clock domain analysis

Description

In reviewingthe unconstrained path analysis in Timing Analyzer, I see the following:

Timing constraint: Unconstrained OFFSET IN BEFORE analysis for clock "CLK"
Timing constraint: Unconstrained OFFSET OUT AFTER analysis for clock "CLK"
Timing constraint: Unconstrained PERIOD analysis for net "CLK"

However, when you have an unconstrained path crossing clock domains, then this is reported as a standard unconstrained path rather than an unconstrained PERIOD. This is similar to how asynchronous paths are shown as follows:

Timing constraint: Unconstrained path analysis

Solution

The timing engine has found paths that would naturally fall into these OFFSET IN/OUT and PERIOD constraints for this given clock signal. Please review these paths and make sure they are not constrainted incorrectly with a TIG constraint or unrelated PERIOD constraint.

AR# 35886
Date Created 11/13/2012
Last Updated 11/13/2012
Status Active
Type General Article
Tools
  • ISE Design Suite - 12.1
  • ISE Design Suite - 12.2
  • ISE Design Suite - 12.3
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