Finite State Machines

Model sequential behaviour as states and transitions — Moore and Mealy machines.

Intermediate

An FSM has a finite set of states, inputs that trigger transitions, and outputs:

Moore — outputs depend only on the current state.
Mealy — outputs depend on the state and the inputs (react one cycle faster).

Examples: traffic lights, vending machines, protocol decoders, button debouncers. In software:

switch (state) {
    case IDLE:    if (start) state = RUNNING; break;
    case RUNNING: if (fault) state = ERROR; else if (done) state = IDLE; break;
    case ERROR:   if (reset) state = IDLE; break;
}

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