时序约束保持时间的两项检查有什么区别

wsk0523

quartus prime的时序分析手册中提到，The Timing Analyzer peRForms two hold checks for each setup relationship. The first
2 s! {' }; k0 r# r/ \' C6 lhold check determines that the data launched by the current launch edge is not
captured by the previous latch edge. The second hold check determines that the data
/ t5 A; N2 X  q0 Q' Vlaunched by the next launch edge is not captured by the current latch edge.  为什么要分成这两种方式，这有什么区别。
; d2 B- W/ K" s! |" k

lingling555

第一次保持检查确定由当前启动边沿启动的数据未被先前的锁存器沿捕获。