The Forgotten Default State
Unmapped states in finite state machines cause unpredictable behavior during power-up or radiation events. A 3-bit next-state logic block uses 5 valid states and must route the remaining 3 unused states to a safe reset state.
Expected behavior:
| S2 | S1 | S0 | N2 | N1 | N0 | |---|---|---|---|---|---| | 0 | 0 | 0 | 0 | 0 | 1 | | 0 | 0 | 1 | 0 | 1 | 0 | | 0 | 1 | 0 | 0 | 1 | 1 | | 0 | 1 | 1 | 1 | 0 | 0 | | 1 | 0 | 0 | 0 | 0 | 0 | | 1 | 0 | 1 | 0 | 0 | 0 | | 1 | 1 | 0 | 0 | 0 | 0 | | 1 | 1 | 1 | 0 | 0 | 0 |
Simulation shows N2 = 1, N1 = 0, N0 = 0 for input state S2 = 1, S1 = 1, S0 = 1. The unmapped state fails to transition to the reset state 000. Inspect the circuit and correct the fault.
Constraints
- Do not add new input or output pins.
- Ensure all 3 unused states strictly transition to
000.
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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