Edge-triggering polarity: A positive edge-triggered flip-flop changes state on a HIGH-to-LOW clock transition. Evaluate the statement.
Correct Answer: Incorrect
Introduction / Context:Edge-triggered devices respond on a specific transition of the clock: positive (rising) or negative (falling). Understanding clock polarity is essential for timing design and multi-stage pipelines.
Given Data / Assumptions:
- Positive edge-triggered means action on LOW-to-HIGH transition.
- Negative edge-triggered means action on HIGH-to-LOW transition.
- Clock-to-output delay follows the triggering edge.
Concept / Approach:The statement claims a positive edge-triggered device reacts on a falling edge (HIGH-to-LOW), which contradicts the definition. Therefore, the statement must be judged incorrect.
Step-by-Step Solution:
Recall: Positive edge = rising edge = LOW-to-HIGH.Given statement: “changes on HIGH-to-LOW.” That is a falling edge.Thus, the statement mislabels the triggering edge.Conclusion: The statement is incorrect.Verification / Alternative check:Datasheets use a triangle or up-arrow symbol near the clock for positive edge; a down-arrow for negative edge. Rising edges are explicitly indicated as 0→1 transitions.
Why Other Options Are Wrong:
Correct: Would agree with the false claim; not acceptable.“True only for master–slave” or “with Schmitt clocks”: Edge polarity is independent of these details.Common Pitfalls:Confusing edge polarity; overlooking that duty cycle does not affect which edge triggers (only timing margins do).
Final Answer:Incorrect