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Codiode/Problems/Sequential Logic

D Latch: Transparency Hazard with Combinational Glitches

HardLogic CircuitTiming Diagram

A D latch is transparent when GATE is HIGH, immediately passing all input changes to the output, while a positive-edge-triggered D flip-flop captures D only exactly on the LOW-to-HIGH transition of GATE.

Four signals are shown: GATE (control input), D (data input driven by an upstream combinational block), Q_LATCH (latch output, initially 0), and Q_DFF (flip-flop output, initially 0).

Trace Q_LATCH and Q_DFF across all 14 time steps to observe how the flip-flop filters out the combinational glitches that the latch allows to pass through.

Constraints

  • Q_LATCH must follow D continuously whenever GATE is 1 and hold its value when GATE is 0.
  • Q_DFF must only update its value when GATE transitions from 0 to 1 and hold its value at all other times.

Topics

HazardsLatchesFlip-FlopsTiming

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Place the gates, wire them up and watch the signals settle. Every submission runs on the same simulation engine that grades it.

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