Master–slave JK flip-flop timing: in a JK master-slave configuration, when is the master latch enabled and when does the slave latch update?

Introduction / Context:The master–slave JK flip-flop is a classic edge-effective memory element built from two level-sensitive latches. Understanding which latch is active on which clock level explains why the pair behaves like an edge-triggered device and avoids race-through problems.

Given Data / Assumptions:

• Level-sensitive master and slave latches are cascaded.
• Single clock controls both, with complementary enabling.
• Positive level enables the master; negative level enables the slave (for the standard convention).

Concept / Approach:During the high phase of the clock, the master latch is transparent and can capture changes at J/K (subject to gating). When the clock goes low, the master closes, and the slave latch becomes transparent, taking the master’s stored state to the output, emulating a falling-edge triggered update.

Step-by-Step Solution:Clock high → master enabled (transparent), slave disabled.Clock low → master disabled (holds), slave enabled (updates Q).Thus the succinct timing is “high, low.”

Verification / Alternative check:Timing diagrams show input sampling while CLK is high and output transfer on the transition to low. This stagger prevents immediate input changes from racing to the output.

Why Other Options Are Wrong:set/reset: describe states, not clock levels.race/no change: not a clock-level pairing.set/race: mismatched terms unrelated to clock polarity.None: incorrect because “high, low” is the established description.

Common Pitfalls:Confusing master–slave with true edge-triggered FFs; forgetting that implementation details vary with active-high vs. active-low conventions.

Final Answer:high, low