Positive edge-triggered D flip-flop operation Which statement best describes how a positive edge-triggered D-type flip-flop transfers data from D to Q?

Introduction / Context:
Edge-triggered flip-flops are the building blocks of synchronous digital systems. A positive edge-triggered D flip-flop samples its data input D precisely at the rising edge of the clock and immediately updates its output Q accordingly, holding that value until the next active edge. This behavior supports precise timing and state sequencing in registers and pipelines.

Given Data / Assumptions:

• Positive edge-triggered topology (rising-edge sensitive).
• Setup and hold times around the clock edge are satisfied.
• Single data input D with complementary outputs Q and Q̄.

Concept / Approach:

Unlike level-sensitive latches, an edge-triggered D flip-flop is insensitive to D during the rest of the clock cycle (beyond setup/hold windows). At the instant of the rising edge, the value on D is captured and immediately appears at Q; it remains held until the next rising edge.

Step-by-Step Explanation:

Verification / Alternative check:

Datasheet timing diagrams show a vertical transfer at the rising edge. Simulation waveforms confirm Q updates only on the leading edge and stays constant otherwise.

Why Other Options Are Wrong:

• (a) Toggle behavior is characteristic of T or J–K devices under specific inputs, not D flip-flops.
• (c) There is no invalid “both inputs LOW” condition for a single-input D device.
• (d) Immediate update occurs at the rising edge; there is no delayed transfer to the trailing edge.
• (e) Continuous updating describes a transparent latch, not an edge-triggered flip-flop.

Common Pitfalls:

• Violating setup/hold times, which can cause metastability.
• Confusing level-sensitive latches with edge-triggered flip-flops in mixed-clock designs.

Final Answer:

The output will follow the input on the leading edge of the clock.