Difference between mealy and moore state machine

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Arvind
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Difference between mealy and moore state machine

Post by Arvind » Fri Apr 11, 2014 8:36 pm

What is the difference between mealy and moore state machine?

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Narveer
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Re: Difference between mealy and moore state machine

Post by Narveer » Sun May 11, 2014 12:06 pm

A) Mealy and Moore models are the basic models of state machines. A state machine which uses only Entry Actions, so that its output depends on the state, is called a Moore model. A state machine which uses only Input Actions, so that the output depends on the state and also on inputs, is called a Mealy model. The models selected will influence a design but there are no general indications as to which model is better. Choice of a model depends on the application, execution means (for instance, hardware systems are usually best realized as Moore models) and personal preferences of a designer or programmer.

B) Mealy machine has outputs that depend on the state and input (thus, the FSM has the output written on edges) Moore machine has outputs that depend on state only (thus, the FSM has the output written in the state itself.

Advantages and Disadvantages:
In Mealy as the output variable is a function both input and state, changes of state of the state variables will be delayed with respect to changes of signal level in the input variables, there are possibilities of glitches appearing in the output variables. Moore overcomes glitches as output dependent on only states and not the input signal level.
All of the concepts can be applied to Moore-model state machines because any Moore state machine can be implemented as a Mealy state machine, although the converse is not true. Moore machine: the outputs are properties of states themselves... which means that you get the output after the machine reaches a particular state, or to get some output your machine has to be taken to a state which provides you the output.The outputs are held until you go to some other state Mealy machine: Mealy machines give you outputs instantly, that is immediately upon receiving input, but the output is not held after that clock cycle.

jesica1
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Re: Difference between mealy and moore state machine

Post by jesica1 » Sat Dec 26, 2015 5:10 pm

Good answer, thanku. :D

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