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Altera_Forum's avatar
Altera_Forum
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16 years ago

Timequest Report Metastability

Timequest seems to ignore all synchronization chains except those contained in a megafunction DCFIFO. For example with the following clock definitions: create_clock -period "30.000 ns" -name ...
Altera_Forum's avatar
Altera_Forum
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16 years ago

If you go to Assignments -> Settings -> TimingQuest and set the metastability to Forced if Asynchronous, it will identify it. In general, this setting is too conservative for most designs, i.e. it will find asynchronous transfers where metastability is not a concern, and use them in its MTBF calculations. If that's the case, set this to Auto, so it will identify all asynchronous transfers but not do MTBF calculations. From that list you can force it on specific chains, i.e. do:

set_instance_assignment -name SYNCHRONIZER_IDENTIFICATION "FORCED IF ASYNCHRONOUS" -to sync[0]

It will then identify that chain. (FIFOs have this built into them, since it's Altera's IP and they know it needs this analysis)