Timing analysis and CDC
In a flip-flop with asynchronous reset, which STA check examines whether reset deassertion is too close to a clock edge?
- AClock gating check
- BRecovery and removal checks
- CMaximum transition (max transition) check
Show answer and explanation
Answer: B. Recovery and removal checks
Like a data input, deassertion of an asynchronous reset must be a certain time away from the clock edge. The recovery check (equivalent to setup) looks at whether deassertion comes too soon before the edge, and the removal check (equivalent to hold) at whether it comes too soon after the edge. A violation makes it uncertain whether reset is released in that cycle, so different flip-flops may start operating in different cycles. The transition check looks at the slew of signal waveforms and serves a different purpose.