Setup Time ()

Minimum time before active clock edge that input must remain stable.

Properties

  • A Flip-Flop requires to correctly sample the current clock cycle input. This determines maximum clock frequency.
  • slack is

where,

  • : delay from preceding flip-flop
  • : delay from Combinatorial Logic after preceding flip-flop
  • : setup time for receiving flip-flop
  • : clock difference between preceding and receiving flip-flop

Analysis

A Flip-Flop stores the input signal with a Latch during the inactive clock. The time from the received input to this latch grasping the value is called .
If the clock transitions during , the flip-flop becomes Metastable and the output is unpredictable.

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