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1、电子与信息工程学院本科毕业论文(设计)外文文献翻译译文题目：ProgrammablelogiccontrollersHardware,softwarearchitecture学生姓名：吴凡专业：电气工程及其自动化指导教师：李东京2012年12月Programmablelogiccontrollers:Hardware,softwarearchitectureManyrespects,thearchitectureoftheprogrammablelogiccontroller(PLC)resemblesageneral-purposecomputerwithspecializedinp
2、ut/output(I/O)modules.However,someimportantcharacteristicsdistinguishaPLCfromageneral-purposecomputer.Mostimportant,aPLCismuchmorereliable,designedforameantimebetweenfailuresmeasuredinyears.Second,aPLCcanbeplacedinanindustrialenvironmentwithitssubstantialamountofelectricalnoise,vibration,extreme
3、temperatures,andhumidity.Third,PLCsareeasilymaintainedbyplanttechnicians.BasicPLChardwarearchitectureThebasicarchitectureofaPLCconsistsofmaincomponents-theprocessormodule,thepowersupply,andtheI/Omodules.Theprocessormoduleconsistsofthecentralprocessingunit(CPU)andmemory.Inadditiontoamicroprocesso
4、r,theCPUalsocontainsatleastaninterfacetoaprogrammingdeviceandmaycontaininterfacestoremoteI/Oandothercommunicationnetworks.Thepowersupplyisusuallyaseparatemodule,andtheI/Omodulesareseparatefromtheprocessor.ThetypesofI/Omodulesincludediscrete(on/off),analog(continuousvariable),andspecialmoduleslik
5、emotioncontrolorhigh-speedcounters.ThefielddevicesareconnectedtotheI/Omodules.DependingontheamountofI/OandtheparticularPLCprocessor,theI/Omodulesmaybeinthesamechassisastheprocessorand/orinoneormoreotherchassis.Upuntilthelate1980s,theI/OmodulesinatypicalPLCsystemwereinchassisseparatefromthePLCpro
6、cessor.Inthemoretypicalpresent-dayPLC,someoftheI/Omodulesarepresentinthechassisthatcontainstheprocessor.SomePLCsystemsallowmorethanoneprocessorinthesamechassis.SmallerPLCsareoftenmountedonaDINrail.ThesmallestPLCs(oftencalledmicro-PLCsornaon-PLCs)includethepowersupply,processor,andalloftheI/Osino
7、nepack-age.Somemicro-PLCscontainabuilt-inoperatorinterfacepanel.Formanymicro-PLCs,theamountofI/Oislimitedandnotexpandable.Basicsoftware,memoryarchitecture(IEC61131-3)TheIEC61131-3standarddefinesamemoryandprogrammodelthatfoll
