Edge-triggered J–K flip-flops — clarity of sampling instant State whether the statement is correct or incorrect: “Edge-triggered J–K flip-flops make it hard for design engineers to know when to accept (sample) input data.”

Introduction / Context:
Edge-triggered flip-flops are widely used because they define an exact instant at which input data are sampled. The claim that they make it “hard to know when to accept input data” conflicts with their design purpose. This item checks your understanding of timing behavior for edge-triggered J–K flip-flops and why they simplify, not complicate, data acceptance.

Given Data / Assumptions:

• The device is an edge-triggered J–K flip-flop (often represented with a triangle on the clock input).
• Inputs J and K are sampled at a specific clock edge (rising or falling as specified).
• Standard timing specs apply: setup time (tSU) and hold time (tH) around the active edge; propagation delay tPLH/tPHL from clock edge to output response.

Concept / Approach:
Edge-triggered devices capture data only at the defined active edge. Designers ensure input signals meet setup/hold windows around that edge. After the edge, the output changes after a finite propagation delay. This model provides a clear “sampling instant,” greatly simplifying synchronous design compared with level-triggered (transparent) latches that can pass glitches while enabled.

Step-by-Step Solution:
Identify active edge (e.g., rising edge for a device with a triangle symbol and no bubble).Guarantee J and K are stable for at least tSU before the edge and tH after the edge.After the edge, the flip-flop output updates after tPLH or tPHL depending on its previous state and inputs.Therefore, the sampling moment is explicit, not ambiguous.

Verification / Alternative check:
Timing diagrams show a narrow capture instant at the clock edge. Static timing analysis in synchronous design is built around these edges and tSU/tH constraints, confirming the predictability of data acceptance.

Why Other Options Are Wrong:
“Correct” contradicts the role of edge triggering. “Only true for negative-edge devices” is incorrect; edge polarity does not add ambiguity. “True only for master–slave types” is also incorrect; master–slave or single-edge behavior still samples at a defined edge.

Common Pitfalls:
Confusing edge-triggered flip-flops with level-sensitive latches; ignoring setup/hold leading to metastability; assuming output updates exactly at the edge rather than after propagation delay.

Final Answer:
Incorrect