|
|
| Line 1: |
Line 1: |
| In the [[theory of computation]], a '''Mealy machine''' is a [[finite-state machine]] whose output values are determined both by its current [[state (computer science)|state]] and the current inputs. (This is in contrast to a [[Moore machine]], whose output values are determined solely by its current state.)
| | Eusebio Stanfill is what's indicated on my birth document although it is in no way the name on particular birth certificate. Vermont can be where my home can. Software making has been my afternoon job for a but. To cook is the only sport my wife doesn't agree to. You can acquire my website here: http://prometeu.net<br><br>My web-site; clash of clans hack tool ([http://prometeu.net relevant site]) |
| A Mealy machine is a [[deterministic automaton|deterministic]] [[finite state transducer]]: for each state and input, at most one transition is possible.
| |
| | |
| ==History==
| |
| The Mealy machine is named after [[George H. Mealy]], who presented the concept in a 1955 paper, “A Method for Synthesizing Sequential Circuits”.<ref>{{cite journal| last=Mealy| first=George H.| title=A Method for Synthesizing Sequential Circuits| journal=Bell Systems Technical Journal| volume=34| pages=1045–1079|date=September 1955}}</ref>
| |
| | |
| ==Formal definition==
| |
| | |
| A Mealy machine is a [[n-tuple|6-tuple]], (''S'', ''S''<sub>0</sub>, Σ, Λ, ''T'', ''G''), consisting of the following:
| |
| * a [[finite set]] of [[State (computer science)|states]] (''S'')
| |
| * a start state (also called initial state) ''S''<sub>0</sub> which is an element of (''S'')
| |
| * a [[finite set]] called the input alphabet (Σ)
| |
| * a [[finite set]] called the output alphabet (Λ)
| |
| * a transition [[function (mathematics)|function]] (''T'' : ''S'' × Σ → ''S'') mapping pairs of a state and an input symbol to the corresponding next state.
| |
| * an output function (''G'' : ''S'' × Σ → Λ) mapping pairs of a state and an input symbol to the corresponding output symbol.
| |
| | |
| In some formulations, the transition and output functions are coalesced into a single function (''T'' : ''S'' × Σ → ''S'' × Λ).
| |
| | |
| ==Diagram==
| |
| The [[state diagram]] for a Mealy machine associates an output value with each transition edge (in contrast to the state diagram for a Moore machine, which associates an output value with each state).
| |
| | |
| When the input and output alphabet are both Σ, one can also associate to a Mealy Automata an Helix [[directed graph]].<ref>{{cite journal|last=Akhavi|first=Ali|coauthors=Ines Klimann, Sylvain Lombardy, Jean Mairesse, Matthieu Picantin|title=On the finiteness Problem for Automaton (Semi)groups|journal=arXiv|date=25 May 2011|url=http://arxiv.org/abs/1105.4725}}</ref> <math>(S \times \Sigma, (x,i)\rightarrow (T(x,i),G(x,i)))</math> This graph has as vertices the couples of state and letters, every nodes are of out-degree one, and the successor of <math>(x,i)</math> is the next state of the automata and the letter that the automata output when it is instate <math>x</math> and it reads letter <math>i</math>. This graph is a union of cycle iff the automaton is bireversible.
| |
| | |
| ==Examples==
| |
| | |
| ===Simple ===
| |
| [[File:Mealy.png|thumb|169px|[[State diagram]] for a simple Mealy machine with one input and one output.]]
| |
| A simple Mealy machine has one input and one output. Each transition edge is labeled with the value of the input (shown in red) and the value of the output (shown in blue).{{nbsp}} The machine starts in state S<sub>i</sub>.{{nbsp}} (In this example, the output is the [[exclusive or|exclusive-or]] of the two most-recent input values; thus, the machine implements an edge detector, outputting a one every time the input flips and a zero otherwise.){{nbsp}}
| |
| | |
| === Complex ===
| |
| More complex Mealy machines can have multiple inputs as well as multiple outputs.
| |
| | |
| ==Applications==
| |
| | |
| Mealy machines provide a rudimentary mathematical model for cipher machines. Considering the input and output alphabet the [[Latin alphabet]], for example, then a Mealy machine can be designed that given a string of letters (a sequence of inputs) can process it into a ciphered string (a sequence of outputs). However, although one could use a Mealy model to describe the [[Enigma machine|Enigma]], the state diagram would be too complex to provide feasible means of designing complex ciphering machines.
| |
| | |
| == See also ==
| |
| * [[Synchronous circuit]]
| |
| * [[Moore machine]]
| |
| * [[Algorithmic State Machine]]
| |
| | |
| == Footnotes ==
| |
| {{Reflist}}
| |
| | |
| == References ==
| |
| *{{cite book
| |
| | last = Mealy
| |
| | first = George H.
| |
| | title = A Method to Synthesizing Sequential Circuits
| |
| | publisher = Bell System Technical Journal
| |
| | year = 1955
| |
| | pages = 1045–1079
| |
| }}
| |
| | |
| *{{cite book
| |
| | last = Roth
| |
| | first = Charles H., Jr.
| |
| | title = Fundamentals of Logic Design
| |
| | publisher = Thomson-Engineering
| |
| | year = 2004
| |
| | pages = 364–367
| |
| | isbn = 0-534-37804-8
| |
| }}
| |
| | |
| *{{cite news
| |
| | last = Akhavi
| |
| | first = Ali
| |
| | title = On the Finiteness Problem for Automaton (Semi)groups
| |
| | date = 25 May 2011
| |
| | url = http://arxiv.org/abs/1105.4725
| |
| }}
| |
| | |
| [[Category:Models of computation]]
| |
Eusebio Stanfill is what's indicated on my birth document although it is in no way the name on particular birth certificate. Vermont can be where my home can. Software making has been my afternoon job for a but. To cook is the only sport my wife doesn't agree to. You can acquire my website here: http://prometeu.net
My web-site; clash of clans hack tool (relevant site)