Cross-coupled NOR latch polarity For a cross-coupled NOR flip-flop (latch), are the set and reset control inputs active-HIGH or active-LOW?

Introduction / Context:
Cross-coupled latches can be realized with either NOR or NAND gates. Their input polarities differ: understanding which version uses active-HIGH versus active-LOW controls is essential for interfacing with the rest of a digital system.

Given Data / Assumptions:

• Device: cross-coupled NOR latch.
• Inputs: S (set) and R (reset) applied to NOR gate inputs.
• Outputs: Q and Q̄ taken from the gates’ outputs in the standard configuration.

Concept / Approach:
A NOR gate outputs HIGH only when all inputs are LOW. Therefore, applying a HIGH on one input forces that NOR output LOW, which—through cross-coupling—drives the opposite output HIGH. Thus, asserting a HIGH on S sets Q=1; asserting a HIGH on R resets Q=0. Hence the NOR latch uses active-HIGH set and reset inputs.

Step-by-Step Solution:

Verification / Alternative check:
Compare with the NAND latch: it uses active-LOW controls (asserting a LOW performs the action). The two are duals with inverted input polarities.

Why Other Options Are Wrong:

• active-LOW: That describes the NAND-based latch, not NOR-based.
• Both / neither: Input polarity is well-defined; the latch is level-sensitive to explicit HIGH assertions for control.

Common Pitfalls:
Mixing up NOR and NAND latch conventions, or assuming output inversion changes input active level (it does not).

Final Answer:
active-HIGH