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Codiode/Problems/Sequential Logic

Counter: Single Wrong Transition Diagnosis

HardLogic CircuitDebug

A custom sequence counter controls the timing phases of a digital communication protocol. The counter must produce the continuous state sequence 3, 4, 5, 6, 7, repeating back to 3.

Expected behavior:

| Q2 | Q1 | Q0 | Next_Q2 | Next_Q1 | Next_Q0 | |------|------|------|-----------|-----------|-----------| | 0 | 1 | 1 | 1 | 0 | 0 | | 1 | 0 | 0 | 1 | 0 | 1 | | 1 | 0 | 1 | 1 | 1 | 0 | | 1 | 1 | 0 | 1 | 1 | 1 | | 1 | 1 | 1 | 0 | 1 | 1 |

Simulation shows the observed sequence is 3, 5, 4, 7, 6, 3. State 3 (011) incorrectly transitions to 5 (101). State 4 (100) incorrectly transitions to 7 (111).

Inspect the circuit and correct the fault.

Constraints

  • Do not modify the clock or reset networks.
  • Do not add additional flip-flops.
  • Only replace or rewire the existing faulty logic gates.

Topics

DebuggingSequential LogicCountersState Machines

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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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