Recovery time is the minimum length of time an asynchronous control signal, for example, and preset, must be stable before the next active clock edge. The recovery slack time calculation is similar to the clock setup slack time calculation, but it applies asynchronous control signals.
Removal time is the minimum length of time an asynchronous control signal must be stable after the active clock edge. The TimeQuest analyzer removal time slack calculation is similar to the clock hold slack calculation, but it applies asynchronous control signals.
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recovery time specifies the time the inactive edge of the asynchronous signal has to arrive before the closing edge of the clock.
Removal time specifies the length of time the active phase of the asynchronous signal has to be held after the closing edge of the clock.
也就是说recovery time和removal time都是检查异步信号（reset或preset或set）的释放沿，释放沿必须在时钟沿前面提前recovery time释放，或者在时钟沿后removal time之后释放
