Asynchronous resets are bad design practice. Reset your flops synchronously or not at all.https://twitter.com/iowahawkblog/status/932309842123022336 …
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In most standard cell libraries that I used DFF with async reset smaller then DFF with sync reset. 90% of projects I worked over last 20 years, async reset was BKM
Yes, it is incredibly wide spread and most people who use it are completely unaware of all the things that could go wrong with it. That's why it's my "most trivial hill on which I am willing to die". :)
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Re size: That's why I added the "or not at all" part. Most flops in a design actually don't need resetting. If area is a concern: Only reset the flops that actually need resetting. No reset needs even less area than async reset.
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At least thinking about size of sync vs async rest _is_ thinking about it. AFAICT, many designers either don't consider sync vs async reset at all, or have a _very_ mistaken idea that async reset is somehow better.
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