Terminology in flip-flop triggering: If an input responds specifically to a signal transition (rising or falling), that input is described as __________.

Introduction / Context:
In sequential logic, the way a storage element responds to its control input critically affects timing analyses and race avoidance. Designers must distinguish between edge-triggered behavior, which samples on transitions, and level-sensitive behavior, which responds while an enable level is present.

Given Data / Assumptions:

• We consider standard digital storage elements such as D, T, J–K, and S–R flip-flops/latches.
• “Signal transition” refers to a change in logic level, e.g., low-to-high (rising edge) or high-to-low (falling edge).

Concept / Approach:
An input that causes action only at the moment of a transition is termed edge-triggered. Typical notations include a triangle on the clock pin for edge-triggered flip-flops and an added bubble for negative-edge triggering. In contrast, “level-triggered” or pulse-triggered devices respond for the duration of an enable level or pulse width, not just at a boundary instant.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets and timing diagrams show edge-triggered devices sampling inputs at clock edges (tSU/tH constraints), while level-sensitive devices have transparent intervals; this confirms the terminology.

Why Other Options Are Wrong:

• Clock-triggered: Too broad—could be level- or edge-sensitive.
• Toggle-triggered: Refers to T flip-flop behavior when T=1, not generalized transition sensitivity.
• Noise-triggered: Undesirable and not a design feature.
• Level-enabled: Opposite of edge-triggered; responds to level duration.

Common Pitfalls:
Confusing “pulse-triggered” (responds while pulse is active) with “edge-triggered” (responds only at the boundary). Always inspect the clock symbol and timing specs in the datasheet.

Final Answer:
edge-triggered