The Dead One Hot Machine
A one-hot state machine requires exactly one active state bit at any given time to function safely. The combinational next-state logic for this 4-bit machine must advance the active bit sequentially and automatically jump-start the system to state 0001 if it ever falls into the invalid all-zero state.
Expected behavior:
| Q3 | Q2 | Q1 | Q0 | D3 | D2 | D1 | D0 | |------|------|------|------|------|------|------|------| | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | | 1 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | | 1 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 |
Simulation shows D0 = 0 for input Q3=0, Q2=0, Q1=0, Q0=0. The machine fails to recover from the all-zero state and remains completely dead. Inspect the circuit and correct the fault.
Constraints
- You must fix the combinational logic to handle the recovery state automatically.
- Do not add an external reset pin to the circuit.
Topics
Solve this problem
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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