2.8 Setup and Hold Times

• Two timing requirements must be met if a clocked FF is to respond reliably to its control inputs when the active CLK transition occurs
• The setup time is the time interval immediately preceding the active transition of the CLK signal, during which the synchronous input has to be maintained at the proper level
• The hold time is the time interval immediately following the active transition of the CLK signal, during which the synchronous input has to be maintained at the proper level
• Synchronous inputs must be stable for setup time range prior to the clock transition, and for hold time range after the clock transition