Synchronizer failure

• Occurs when FF input changes close to the clock edge

  • The input is neither logic 1 nor logic 0 when the clock goes high
  • The output may be neither a logic 0 nor a logic 1
  • The output may stay in this undefined state for a long time
  • The undefined state is called metastability

logic 0

logic 1

D

CLK

Q

?

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