Re: Exact Timing Constraints vs. Over-Constraining

When you implement double synchronizers, make sure that the two
flip-flops are closely spaced ( e.g. in the same slice ) with minimal
routing delay between them. Overconstrain this delay between them (
enforce a few ns ) so that you do not squander the time available for
metastable resolution.

Remember: The software takes your constraint requests literally. Once
they are met, the software does nothing to make it any better ( why
should it? ), the way a good engineer might naturally be inclined to do it...
It's just a computer!

Peter Alfke
======================
Larry Doolittle wrote: 
> An alternative approach (I have seen other people do this) is to put
> two stages of flip-flops on all clock-domain crossings, and _assume_
> there is a ton of slack between them.
> 
>     - Larry