Solution ID: rd06282006_610
Last Modified: Sep 11, 2012
Product Category: Design Software
Product Area: Timing Analysis
Product Sub-area: QII Classic Timing Analysis
Software: Quartus II PC
Device Family: STRATIX II
Why do I see many unconstrained setup and hold paths in the Quartus II software version 6.0 when I have paths that cross clock domains?
In the Quartus® II software, the Cut Paths Between Unrelated Clock Domains option is turned on by default. Beginning with the Quartus II software version 6.0, this setting causes the software to ignore all setup and hold constraints on paths that cross unrelated clock domains. The Quartus II Classic Timing Analyzer reports paths crossing unrelated clock domains as unconstrained.
This reporting did not occur in previous versions of Quartus II software. To avoid these warnings, turn off Cut Paths Between Unrelated Clock Domains. To prevent timing analysis on specific paths, make an individual cut path assignment for each relevant path.
Altera does not warrant that this solution will work for the customer's intended purpose and disclaims all liability for use of or reliance on the solution.