Verification
Reset Domain Crossing: The Cousin of CDC Everyone Forgets
Clock domain crossing checks sit on almost every sign-off list. Reset domain crossing checks often do not, even though an RDC needs no second clock at all. Two flops on one clock, each with its own asynchronous reset, joined by a wire, are enough. Assert the launching flop's reset and its output changes at a moment that has nothing to do with the clock. This post is for RTL and verification engineers. It shows how these bugs arise, why the…