Question

Which element of JK flip-flop operates in toggle mode when clock pulse is applied?

• A. S
• B. R
• C. J
• D. J and K

Hint:

JK = 1,1 → toggle mode.

Answer 1

The Correct Option is D

Step 1: Recall the JK flip-flop's four input combinations.
A JK flip-flop can be told to hold its state, reset to 0, set to 1, or toggle, depending on the values placed on its J and K inputs, and the action only takes effect when the clock edge arrives.
Step 2: Write the next-state rule.
The next state is given by $Q_{next} = J\overline{Q} + \overline{K}Q$. If you substitute $J = 1$ and $K = 1$ into this expression, it simplifies to $Q_{next} = \overline{Q}$, meaning the output simply flips to the opposite of whatever it currently is.
Step 3: Connect this to toggle mode.
Since flipping the output every clock pulse is exactly what toggle means, and this only happens when both J and K are held high together, both inputs are jointly responsible for the toggle action.
\[ \boxed{J \text{ and } K} \]