Difference Between Mealy Machine and Moore Machine

Mealy Machine Vs. Moore Machine: Explore What is the Difference Between Mealy Machine and Moore Machine?

In this article, we will discuss the major ways in which both the machines vary. But before we dig deeper into the difference between Mealy Machine and Moore Machine- we will first look into what they do individually.

What is a Mealy Machine?

In the computation theory, we refer to a Mealy Machine as a finite-state machine. In a Mealy machine, we determine the output values by both- the current inputs and the current state.

One can describe a Mealy machine by a 6 tuple of Q, δ, Ʃ, O, X, q0. Here:

  • q0 – It is the very initial state for a user, from where they can process any input (q0 ϵQ)
  • X – It is the transition function for output. Here, X:Q x Ʃ―>O
  • δ – It is the transition function for input. Here, δ:Q x Ʃ ―>Q
  • Ʃ – It is a set of symbols (finite), also known as the input alphabets.
  • O – It is a set of symbols (finite), also known as the output alphabets.
  • Q – It is a set of states (finite).

Characteristics of a Mealy Machine:

  • A Mealy machine has fewer states as compared to a Moore machine.
  • Based on its present state and the current input, the Mealy machine alters its output.
  • It places its output on the transition.
  • Every Mealy machine reacts to inputs comparatively faster. The reaction occurs in the very same clock cycle.
  • When the input logic is done in the present state, then the value of the output function becomes a function of transitions and changes.
  • A Mealy Machine generally requires only a very few states for the process of synthesis.
  • The asynchronous generation of output through its state alters to synchronous on the present clock.
  • It requires very little hardware for designing a Mealy Machine.
  • The designing process doesn’t need to be very easy.
  • You cannot refer to the counter as a Mealy Machine.

What is a Moore Machine?

In computation theory, we refer to a Moore Machine as a finite-state machine. In a Moore Machine, we determine the output values by their current state only.

One can describe a Moore Machine by a 6 tuple of Q, δ, Ʃ, O, X, q0. Here:

  • q0 – It is the very initial state for a user, from where they can process any input (q0 ϵQ)
  • X – It is the transition function for output. Here, X:Q x Ʃ―>O
  • δ – It is the transition function for input. Here, δ:Q x Ʃ ―>Q
  • Ʃ – It is a set of symbols (finite), also known as the input alphabets.
  • O – It is a set of symbols (finite), also known as the output alphabets.
  • Q – It is a set of states (finite).

Characteristics of a Moore Machine:

  • A Moore Machine consists of more states than the Mealy Machine.
  • Its output does not depend on the current input. It depends only on its current state.
  • It places its output on the transition.
  • Whenever a change occurs in the state, the output function’s value becomes the function of its current state along with the changes at the edges of the clock.
  • The state and output- both change the synchronous to its clock edge.
  • In a Moore Machine, one requires more logic for decoding the output. As a result, it leads to more delays in the circuit. Generally, these react after one clock cycle.
  • One requires more hardware to design a Moore Machine.
  • The states for synthesis required for this machine are also more.
  • It is very easy to design.
  • You can refer to the counter as a Moore Machine.

Difference Between Mealy Machine And Moore Machine

Parameters

Mealy Machine

Moore Machine

Definition

A Mealy Machine changes its output on the basis of its present state and current input.

A Moore Machine’s output depends only on the current state. It does not depend on the current input.

Output

Mealy Machine places its output on the transition.

Moore machine also places its output on the transition.

States

It has comparatively fewer or the same states as that of the Moore machine.

It has comparatively fewer or the same states as that of the Mealy machine.

Value of the Output Function

When the input logic is done in the present state, then the value of the output function becomes a function of transitions and changes.

Whenever a change occurs in the state, the output function’s value becomes the function of its current state along with the changes at the edges of the clock.

Reaction to the Inputs

A Mealy machine reacts comparatively faster to inputs than the Moore machine. Generally, it reacts in the very same clock cycle.

In a Moore Machine, one requires more logic for decoding the output. As a result, it leads to more delays in the circuit. Generally, these react after one clock cycle.

State and Output

The asynchronous generation of output through its state alters to synchronous on the present clock.

The state and output- both change the synchronous to its clock edge.

Requirement of States

A Mealy Machine generally requires only a very few states for the process of synthesis.

The states for synthesis required for this machine are also more.

Requirement of Hardware

It requires very little hardware for designing a Mealy Machine.

One requires more hardware to design a Moore Machine.

Counter

You cannot refer to the counter as a Mealy Machine.

You can refer to the counter as a Moore Machine.

Design

The designing process doesn’t need to be very easy.

It is very easy to design.

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