Effect of asynchronous inputs Do asynchronous inputs (such as preset or clear) cause a flip-flop to respond immediately, independent of the clock input?

Introduction / Context:
Flip-flops generally have two classes of inputs: synchronous inputs that are evaluated with respect to a clock (for example, D, J, K, T) and asynchronous inputs that act immediately (for example, PRE and CLR). Understanding this distinction is crucial for safe reset design, power-on initialization, and robust timing closure.

Given Data / Assumptions:

• Asynchronous inputs are typically labeled preset (PRE) and clear (CLR) and are often active-LOW.
• When asserted, they override normal synchronous operation.
• Clock presence or level is irrelevant to their immediate effect.

Concept / Approach:
Asynchronous controls bypass the clocked input path and directly force the internal storage node to a defined state. For example, PRE forces Q = 1 and CLR forces Q = 0 (polarity depending on the device). Because these signals do not wait for an active clock edge, they are described as causing an immediate response with respect to the clock.

Step-by-Step Solution:

Verification / Alternative check:
Datasheet timing sections specify asynchronous set/reset timing (recovery/removal) separately from synchronous setup/hold, confirming independence from the clock for assertion, but requiring care when deasserting around clock edges.

Why Other Options Are Wrong:

• False: Would imply asynchronous controls wait for the clock, which contradicts their definition and practical behavior.

Common Pitfalls:
Mixing synchronous resets (implemented through clocked logic) with asynchronous resets (through PRE/CLR pins), and failing to respect recovery/removal constraints when releasing asynchronous signals.

Final Answer:
True