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17268 Discussions

seems timeQuest bug in Setup Relationship

Altera_Forum
Honored Contributor II
‎01-05-2016 05:13 AM
1,147 Views

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 timing analysis? 

http://www.alteraforum.com/forum/attachment.php?attachmentid=11662&stc=1  

 

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Altera_Forum
Honored Contributor II
‎01-06-2016 04:16 AM
350 Views

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.

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