Moore machine

Moore model control of a winch door in the theory of computation, a Moore machine is a finite state automaton where the outputs are determined by the current state alone. The state diagram for a Moore machine will include an output signal for each state. Compare with a Mealy machine, which maps transitions in the machine to outputs.

The name Moore machine comes from that of its supporter, Edward F. Moore, a state-machine pioneer who wrote "Gedanken-experiments on Sequential Machines".

Most digital electronic systems are designed as clocked sequential systems. Clocked sequential systems are a limited form of Moore machine where the state changes only when the global clock signal changes. Typically the current state is stored in flip-flops, and a global clock signal is connected to the "clock" input of the flip-flops. Clocked chronological systems are one way to solve met stability problems.

A typical electronic Moore machine includes a combinatorial logic chain to decode the current state into the outputs. The instant the current state changes, those changes ripple through that chain, and almost instantaneously the outputs change. There are design techniques to ensure that no glitches occur on the outputs during that brief period while those changes are rippling through the chain, but most systems are designed so that glitches during that brief transition time are ignored or are irrelevant. The outputs then stay the same indefinitely, until the Moore machine changes state again.