Introduction / Context:
Edge-triggered flip-flops capture input data at a particular clock edge. To ensure reliable operation, the data and control inputs must be stable around that edge. These time windows are known as setup time (before the edge) and hold time (after the edge).
Given Data / Assumptions:
- We consider synchronous data inputs (e.g., D for D-FF, J/K under synchronous use).
- “Active edge” means rising or falling edge that triggers capture.
- Device timing parameters come from datasheets and vary by technology.
Concept / Approach:
Setup time t_setup: the signal must be stable for at least t_setup before the clock edge. Hold time t_hold: the signal must remain stable for at least t_hold after the edge. Violating either can cause metastability or incorrect data capture. Therefore, the statement accurately describes a universal requirement for synchronous inputs to flip-flops.
Step-by-Step Solution:
Ensure data meets t_setup relative to the clock edge.Ensure data meets t_hold following the clock edge.Budget clock skew and propagation delays to maintain margins across the design.Verify in timing analysis tools and with oscilloscope measurements where applicable.
Verification / Alternative check:
Static timing analysis explicitly checks setup/hold constraints between registers; silicon failures often trace to violations.
Why Other Options Are Wrong:
Incorrect: Would ignore well-established timing constraints.Applies only to asynchronous inputs: Asynchronous inputs use different constraints (like pulse width, recovery/removal), not setup/hold.True only for D flip-flops: All clocked flip-flops impose setup/hold on their synchronous data paths.
Common Pitfalls:
Forgetting clock skew/jitter reduces effective timing margins.Confusing asynchronous set/reset with synchronous data timing.
Final Answer:
Correct
Discussion & Comments