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AR# 3285

4.1i Timing Analyzer - A timing analysis reports "0 items analyzed" for a PERIOD constraint.


General Description:

A timing analysis for a PERIOD constraint reports "0 items analyzed." Why does this happen?


If a PERIOD constraint and a FROM:TO cover the same path, the PERIOD constraint is overridden. This conflict also occurs when using the OFFSET constraint with an associated PERIOD constraint and the FROM:TO constraint.

This causes the path to only be reported under the FROM:TO constraint. (The OFFSET and FROM:TO constraints perform similar analysis and normally only one of them is needed.)

This is correct behavior; the user needs to decide what type of constraint to use.

If you wish to use the PERIOD constraint, the solution is to remove the path from the FROM:TO or OFFSET constraint. This will allow the paths to be reported under the PERIOD constraint.

For more information, please see (Xilinx Answer 2435) for other "0 items Analyzed" issues, and see (Xilinx Answer 5747) for information on how constraints are prioritized.

AR# 3285
Date 01/18/2010
Status Archive
Type General Article