Final answer:
A clocked flip-flop requires the control inputs to be stable for a certain duration before the active clock transition. This is known as the minimum setup time (ts). The control inputs must be stable for at least 20nS before the active clock transition.
Step-by-step explanation:
A clocked flip-flop timing diagram
A clocked flip-flop is a type of sequential logic circuit that stores one bit of information. It has two main control inputs, the clock input and the data input. The clock input determines when the flip-flop will change its state based on the data input. The flip-flop has a minimum setup time (ts) and a minimum hold time (tH) that must be met for proper operation.
To ensure the stability of the control inputs prior to the active clock transition, the control inputs must be stable for a duration longer than the minimum setup time (ts). In this case, since ts is given as 20nS, the control inputs must be stable for at least 20nS before the active clock transition.
Timing Diagram:
Clock: ______|█|__________________________|█|______________
Data Input: ___________|█|_______________________
Output: _____________________|█|______________