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Codiode/Problems/Sequential Logic

DFF: Setup Time Violation

MediumLogic CircuitTiming Diagram

A positive-edge-triggered D flip-flop captures the value of D on the LOW-to-HIGH transition of CLK provided D is stable immediately before the edge. Three signals are shown: CLK (clock, period 2), D (input) and Q (output, initially 0). If D transitions at the exact same time step as the CLK rising edge, a setup time violation occurs and Q becomes indeterminate ('X'). Trace Q across all 10 time steps.

Constraints

  • The output must be exactly 0, 1, or "X" for each time step.
  • Use "X" to represent a metastable state caused by a setup time violation.
  • The flip-flop holds its previous state (including "X") when the clock is LOW.

Topics

Sequential LogicMetastabilityTimingLatches and Flip-Flops

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