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Codiode/Problems/Sequential Logic

Pipeline Register Between Combinational Stages

MediumLogic CircuitTiming Diagram

A two-stage pipeline uses a positive-edge-triggered register to isolate two combinational addition stages. Stage 1 computes A XOR B and the pipeline register captures this intermediate result on every LOW-to-HIGH transition of CLK. Stage 2 computes the final output by evaluating the captured register value XORed with C.

Five signals are shown: CLK (clock, period 4), A (Stage 1 input), B (Stage 1 input), C (Stage 2 input), and OUT (Stage 2 output). The pipeline register initially holds 0.

Trace OUT across all 16 time steps.

Constraints

  • The pipeline register only updates its stored value exactly at the LOW-to-HIGH clock transitions.
  • Stage 2 is purely combinational: OUT updates immediately whenever C changes or when the pipeline register updates.
  • Mid-cycle changes to A or B do not affect OUT until the next rising clock edge.

Topics

CombinationalShift RegistersPIPOPipeline

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