Which statement about JK flip-flops is true?

Which statement about JK flip-flops is true?

• A. They use Set and Reset inputs only
• B. They are purely combinational elements
• C. They cannot be used for memory storage
• D. They use J and K inputs and can toggle on a clock edge when J and K are both high

Answer: (D)

JK flip-flops are clocked storage elements that use two inputs, J and K, to steer the next state on a clock edge. The J and K inputs control how the output Q changes: J can set Q to 1, K can reset Q to 0, and when both are high, the flip-flop toggles its state on the triggering clock edge. This toggling behavior is what gives JK flip-flops their versatility for counting and memory tasks. The other statements miss key features. They imply only Set and Reset inputs or claim the device is purely combinational, which ignores the memory and edge-triggered nature of JK flip-flops. They also claim it cannot be used for storage, which is false since JK flip-flops are classic memory elements. Therefore, the statement about using J and K inputs and toggling on a clock edge when both are high is the accurate description.

JK flip-flops are clocked storage elements that use two inputs, J and K, to steer the next state on a clock edge. The J and K inputs control how the output Q changes: J can set Q to 1, K can reset Q to 0, and when both are high, the flip-flop toggles its state on the triggering clock edge. This toggling behavior is what gives JK flip-flops their versatility for counting and memory tasks.

The other statements miss key features. They imply only Set and Reset inputs or claim the device is purely combinational, which ignores the memory and edge-triggered nature of JK flip-flops. They also claim it cannot be used for storage, which is false since JK flip-flops are classic memory elements. Therefore, the statement about using J and K inputs and toggling on a clock edge when both are high is the accurate description.