Why two hold checks done byTimeQuest

Hi,

TimeQuest says it uses two hold checks per each setup check. The first hold check for

previous latch edge with current launch edge and second check for current latch edge

with next launch edge. It then gives a diagram which makes sense as one hold check

could miss the most restrictive case. The diagram is based on different clocks (possibly latch is at half speed). My question is:

who will use such clocking and what about other cases of clock frequency mismatch?

Regards

Kaz

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