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Codiode/Problems/Sequential Logic

Ring Counter: Initialization Waveform Verification

MediumLogic CircuitTiming Diagram

A 4-bit ring counter requires proper initialization to establish its circulating pattern. On every LOW-to-HIGH transition of CLK, the counter shifts its bits right (Q3 to Q2, Q2 to Q1, Q1 to Q0) and feeds Q0 back into Q3, unless LOAD is HIGH. When LOAD is HIGH during a rising clock edge, the counter synchronously loads the valid starting state 1000 (Q3=1, Q2=0, Q1=0, Q0=0).

Six signals are shown: CLK (clock, period 2), LOAD (synchronous initialization input), and the four state outputs Q3, Q2, Q1, and Q0 (all initially 0).

Trace Q3, Q2, Q1, and Q0 across all 16 time steps to observe the all-zeros lockup behavior followed by valid ring circulation.

Constraints

  • The initial state of Q3, Q2, Q1, and Q0 is exactly 0000.
  • Output transitions occur only exactly at the LOW-to-HIGH edge of CLK.
  • The LOAD signal operates synchronously and only takes effect on the rising clock edge.

Topics

sequential-logicshift-registersstate-initialization

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