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Altera_Forum's avatar
Altera_Forum
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10 years ago

seems timeQuest bug in Setup Relationship

I generate two clocks from a 288MHz input clock, one is 96MHz with -30 degree phase shift and another is 288MHz with -90 degree phase shift. Why timeQuest set 'setup relationship' to 0.001ns during t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
10 years ago

Rounding error. If you look at the actual launch and latch edges, they're off by 1ps. This was improved on in TimeQuest a few releases ago, so if using something years old, it might be fixed, but there can still be problems. Using clocks that are multiples of 3 is pretty uncommon. Sometimes tweaking the input clock frequency by a ps or two fixes it.