J-K versus S-R flip-flop: What is the key advantage of the J-K flip-flop when compared to the S-R latch/flip-flop?

Introduction / Context:
The S-R latch has an invalid input condition when both S and R are HIGH simultaneously. The J-K flip-flop extends this behavior to allow a defined toggle action when both inputs are asserted, making it more versatile.

Given Data / Assumptions:

• J-K is edge-triggered in most logic families.
• Inputs J = 1 and K = 1 cause toggling on each active clock edge.
• S-R with S = R = 1 is invalid or forbidden.

Concept / Approach:
The toggle state enables divide-by-2 counters and flexible state machines without additional gating to avoid illegal states, simplifying designs.

Step-by-Step Solution:

Verification / Alternative check:
Construct a divide-by-2 using a single J-K with J=K=1; observe Q toggling each clock.

Why Other Options Are Wrong:

• Much faster: Speed depends on implementation, not a fundamental advantage.
• No propagation delay problems: All real devices have propagation delays.
• Two outputs: Many flip-flops provide Q and not-Q; this is not unique to J-K.

Common Pitfalls:
Assuming J-K eliminates all illegal transitions automatically; race-around must be mitigated by edge triggering or master-slave design.

Final Answer:
The J-K flip-flop has a toggle state.