Prerequisite – Mealy and Moore Machines

**Mealy Machine –** A mealy machine is defined as a machine in theory of computation whose output values are determined by both its current state and current inputs. In this machine atmost one transition is possible.

It has 6 tuples: (Q, q0, ∑, O, δ, λ’)

Q is finite set of states

q0 is the initial state

∑ is the input alphabet

O is the output alphabet

δ is transition function which maps Q×∑ → Q

‘λ’ is the output function which maps Q×∑→ O

**Diagram –**

**Moore Machine –** A moore machine is defined as a machine in theory of computation whose output values are determined only by its current state.

It has also 6 tuples: (Q, q0, ∑, O, δ, λ)

Q is finite set of states

q0 is the initial state

∑ is the input alphabet

O is the output alphabet

δ is transition function which maps Q×∑ → Q

λ is the output function which maps Q → O

**Diagram –**

**Moore Machine –**

- Output depends only upon present state.
- If input changes, output does not change.
- More number of states are required.
- There is more hardware requirement.
- They react slower to inputs(One clock cycle later)
- Synchronous output and state generation.
- Output is placed on states.
- Easy to design.

**Mealy Machine –**

- Output depends on present state as well as present input.
- If input changes, output also changes.
- Less number of states are required.
- There is less hardware requirement.
- They react faster to inputs.
- Asynchronous output generation.
- Output is placed on transitions.
- It is difficult to design.

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