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Codiode/Problems/Sequential Logic

Asynchronous Reset Release: Which Cycle Does Q Recover?

HardLogic CircuitTiming Diagram

A positive-edge-triggered D flip-flop with an active-low asynchronous reset forces its output to 0 immediately when reset is asserted, but resumes normal edge-triggered capture only at the next clock edge after reset is released. Three signals are provided: CLK (clock, period 8), RST_bar (active-low asynchronous reset input), and D (data input). Trace the output signal Q across all 16 time steps given an initial state of 1.

Constraints

  • RST_bar is active-low: it forces Q to 0 immediately at the exact time step it transitions to 0, overriding all other inputs.
  • When RST_bar transitions to 1 (deasserts), Q does not capture the current value of D immediately.
  • The flip-flop only captures D on a LOW-to-HIGH transition of CLK while RST_bar is 1.

Topics

Flip-FlopsAsynchronous ResetTiming Analysis

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