Input levels required to control an S–R flip-flop: For a conventional S–R flip-flop (active-HIGH control inputs), what input level is required on the respective S or R pin to SET or RESET the device?

Introduction / Context:
Flip-flop control inputs can be active-HIGH or active-LOW depending on family and symbol notation. Being able to read symbols and determine which logic level asserts SET or RESET is essential when wiring control lines for initialization and control in synchronous systems.

Given Data / Assumptions:

• We consider the common active-HIGH S–R flip-flop interface (e.g., edge-triggered or level-sensitive with S and R bubbles absent).
• Active-HIGH means a logic HIGH at S asserts SET; a logic HIGH at R asserts RESET.

Concept / Approach:
For active-HIGH S–R flip-flops, the functional inputs S and R respond to a HIGH assertion. An asserted S drives Q to 1; an asserted R drives Q to 0. This is distinct from S–R latches made from NAND gates, which use active-LOW inputs, but the question explicitly targets the conventional active-HIGH case, as is typical for symbol sets without inversion bubbles.

Step-by-Step Solution:

Verification / Alternative check:
Review datasheets: pins labeled /S or /R (with slashes/bubbles) indicate active-LOW; plain S and R (no bubbles) indicate active-HIGH. This symbol convention confirms the answer when “conventional active-HIGH” is assumed.

Why Other Options Are Wrong:

• LOW: Would be true only for active-LOW (bubbled) S–R inputs.
• Steering diodes / limiting resistor / tri-stated: These are wiring details or output conditions, not the necessary logic levels to assert the function.

Common Pitfalls:
Forgetting to read inversion bubbles on logic symbols; mixing NAND-latch conventions (active-LOW) with generalized flip-flop pin behavior (often active-HIGH).

Final Answer:
HIGH