Definition of transparency in latches When is a latch or flip-flop said to be transparent in practical digital design terminology?

Introduction / Context:
Transparency refers to whether the stored element passes input changes directly to the output during a certain control interval. This concept distinguishes level-sensitive latches from edge-triggered flip-flops and is fundamental for timing closure in pipelined and gated data paths.

Given Data / Assumptions:

• Device: level-sensitive latch (for example, D latch) controlled by an enable or gate signal.
• Transparency applies during the active level of the enable.
• Edge-triggered flip-flops are not transparent; they sample only at transitions.

Concept / Approach:
A latch is called transparent when, while enabled, its output Q follows (tracks) the input D essentially in real time, limited only by propagation delay. When the enable is inactive, the latch becomes opaque, holding the last sampled value and blocking further input changes from affecting Q until re-enabled.

Step-by-Step Solution:

Verification / Alternative check:
Timing diagrams show Q tracking D during the enable window and flat otherwise. Simulation confirms that glitches on D may propagate while transparent, underscoring the need for clean combinational inputs during that interval.

Why Other Options Are Wrong:

• Opposite the input: That describes inversion, not transparency.
• See-through packaging: Humorous distractor; unrelated to logic behavior.
• Ignores the input regardless of control: That would be an inoperative or constantly opaque device.

Common Pitfalls:
Assuming flip-flops behave transparently (they do not) and overlooking that transparency can allow hazards or race-through if enable timing is poorly constrained.

Final Answer:
when the Q output follows the input