J–K flip-flop toggle behavior — effect of a TOGGLE (T) command State whether the following is correct: “A TOGGLE input to a J–K flip-flop causes the Q and Q̄ outputs to switch to their opposite states.”

Introduction / Context:
J–K flip-flops are general-purpose sequential elements. When both J and K are asserted (J=1, K=1) at the active clock edge, the device toggles, meaning Q changes to Q̄ and vice versa. Many devices expose this function as a dedicated T (toggle) input by internally tying J and K together.

Given Data / Assumptions:

• An edge-triggered J–K flip-flop is clocked properly and meets setup/hold constraints.
• No asynchronous inputs (PRESET/CLEAR) are overriding the state.
• Toggle condition corresponds to J=K=1 or an external T command translated to that condition.

Concept / Approach:
J=0,K=0 holds state; J=1,K=0 sets Q=1; J=0,K=1 resets Q=0; J=1,K=1 toggles Q. Therefore, under a toggle directive the outputs invert each active clock edge, implementing divide-by-2 counting when driven by a periodic clock.

Step-by-Step Solution:
Apply T (or J=K=1) with the clock at its active edge.Flip-flop recognizes the toggle condition.Q becomes Q̄(previous), and Q̄ becomes Q(previous).On subsequent active edges, the process repeats, producing a square-wave at half the clock frequency.

Verification / Alternative check:
Build a divide-by-2 using a J–K with J=K=1; scope shows Q toggling each clock.

Why Other Options Are Wrong:
“Incorrect” ignores the standard J–K truth table. Preset/Clear dominance is an orthogonal feature; toggle still works when they are inactive. Clock level vs. edge triggering does not negate the definition of the toggle case.

Common Pitfalls:
Violating setup/hold around the edge causes metastability instead of clean toggling; forgetting asynchronous inputs override normal operation.

Final Answer:
Correct