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中英文外文翻译--PLC和微处理器.doc

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中英文外文翻译--PLC和微处理器.doc

INTRODUCTIONSOFPLCANDMCUAPLCISADEVICETHATWASINVENTEDTOREPLACETHENECESSARYSEQUENTIALRELAYCIRCUITSFORMACHINECONTROLTHEPLCWORKSBYLOOKINGATITSINPUTSANDDEPENDINGUPONTHEIRSTATE,TURNINGON/OFFITSOUTPUTSTHEUSERENTERSAPROGRAM,USUALLYVIASOFTWAREORPROGRAMMERTHATGIVESTHEDESIREDRESULTSPLCAREUSEDINMANY“REALWORLD”APPLICATIONSIFTHEREISINDUSTRYPRESENT,CHANCESAREGOODTHATTHEREISAPLCPRESENTIFYOUAREINVOLVEDINMACHINING,PACKAGING,MATERIALHANDLING,AUTOMATEDASSEMBLYORCOUNTLESSOTHERINDUSTRIES,YOUAREPROBABLYALREADYUSINGTHEMIFYOUARENOT,YOUAREWASTINGMONEYANDTIMEALMOSTANYAPPLICATIONTHATNEEDSSOMETYPEOFELECTRICALCONTROLHASNEEDFORPLCFOREXAMPLE,LET’SASSUMETHATWHENASWITCHTURNSONWEWANTTOTURNASOLENOIDONFOR5SECONDSANDTHENTURNITOFFREGARDLESSOFHOWLONGTHESWITCHISONFORWECANDOTHISWITHASIMPLEEXTERNALTIMERWHATIFTHEPROCESSALSONEEDEDTOCOUNTHOWMANYTIMESTHESWITCHINDIVIDUALLYTURNEDONWENEEDALOTOFEXTERNALCOUNTERSASYOUCANSEE,THEBIGGERTHEPROCESSTHEMOREOFANEEDWEHAVEFORAPLCWECANSIMPLYPROGRAMTHEPLCTOCOUNTITSINPUTSANDTURNTHESOLENOIDSONFORTHESPECIFIEDTIMEWEWILLTAKEALOOKATWHATISCONSIDEREDTOBETHE“TOP20”PLCINSTRUCTIONSITCANBESAFELYESTIMATEDTHATWITHAFIRMUNDERSTANDINGOFTHEREINSTRUCTIONSONECANSOLVEMORETHAN80OFTHEAPPLICATIONSINEXISTENCETHAT‘SRIGHT,MORETHAN80OFCOURSEWE’LLLEARNMORETHANJUSTTHESEINSTRUCTIONSTOHELPYOUSOLVEALMOSTALLYOURPOTENTIALPLCAPPLICATIONSTHEPLCMAINLYCONSISTSOFACPU,MEMORYAREAS,ANDAPPROPRIATECIRCUITSTORECEIVEINPUT/OUTPUTDATA,ASSHOWNINFIG191WECANACTUALLYCONSIDERTHEPLCTOBEABOXFULLOFHUNDREDSORTHOUSANDSOFSEPARATERELAYS,COUNTERS,TIMERANDDATESTORAGELOCATIONSDOTHESECOUNTERS,TIMERS,ETCREALLYEXISTNO,THEYDON’T“PHYSICALLY”EXISTBUTRATHERTHEYARESIMULATEDANDCANBECONSIDEREDSOFTWARECOUNTERS,TIMERS,ETCTHESEINTERNALRELAYSARESIMULATEDTHROUGHBITLOCATIONSINREGISTERSWHATDOESEACHPARTDOINPUTRELAYSCONTACTSTHESEARECONNECTEDTOTHEOUTSIDEWORLDTHEYPHYSICALLYEXISTANDRECEIVESIGNALSFROMSWITCHES,SENSORS,ETCTYPICALLYTHEYARENOTRELAYSBUTRATHERTHEYARETRANSISTORSINTERNALUTILITYRELAYSCONTACTSTHESEDONOTRECEIVESIGNALSFROMTHEOUTSIDEWORLDNORDOTHEYPHYSICALLYEXISTTHEYARESIMULATEDRELAYSANDAREWHATENABLESAPLCTOELIMINATEEXTERNALRELAYSTHEREAREALSOSOMESPECIALRELAYSTHATAREDEDICATEDTOPERFORMINGONLYONETASKSOMEAREALWAYSONWHILESOMEAREALWAYSOFFSOMEAREONONLYONCEDURINGPOWERONANDARETYPICALLYUSERFORINITIALIZINGDATAWHATWASSTOREDCOUNTERSTHESEAGAINDONOTPHYSICALLYEXISTTHEYARESIMULATEDCOUNTERSANDTHEYCANBEPROGRAMMEDTOCOUNTPULSESTYPICALLYTHESECOUNTERSCANCOUNTUP,DOWNORBOTHUPANDDOWNSINCETHEREARESIMULATED,THEYARELIMITEDINTHEIRCOUNTINGSPEEDSOMEMANUFACTURERSALSOINCLUDEHIGHSPEEDCOUNTERSTHATAREHARDWAREBASEDWECANTHINKOFTHESEASPHYSICALLYEXISTINGMOSTTIMERSTHESECOUNTERSCANCOUNTUP,DOWNORUPANDDOWNTIMERSTHESEALSODONOTPHYSICALLYEXISTTHEYCOMEINMANYVARIETIESANDINCREMENTSTHEMOSTCOMMONTYPEISANONDELAYTYPEOTHERINCLUDEOFFDELAYANDBOTHRETENTIVEANDNONRETENTIVETYPESINCREMENTSVARYFROM1MSTHROUGH1SOUTPUTRELAYSCOILTHESEARECONNECTEDTOTHEOUTSIDEWORLDTHEYPHYSICALLYEXISTANDSENDON/OFFSIGNALSTOSOLENOIDS,LIGHTS,ETCTHEYCANBETRANSISTORS,RELAYS,ORTRIACSDEPENDINGUPONTHEMODELCHOSENDATASTORAGETYPICALLYTHEREAREREGISTERSASSIGNEDTOSIMPLYSTOREDATATHEREAREUSUALLYUSEDASTEMPORARYSTORAGEFORMATHORDATAMANIPULATIONTHEYCANALSOTYPICALLYBEUSERPOWERUPTHEYWILLSTILLHAVETHESAMECONTENTSASBEFOREPOWERWARREMOVEDVERYCONVENIENTANDNECESSARYAPLCWORKSBYCONTINUALLYSCANNINGAPROGRAMWECANTHINKOFTHISSCANCYCLEASCONSISTINGOF3IMPORTANTSTEPS,ASSHOWNINFIG192THEREARETYPICALLYMORETHAN3BUTWECANFOCUSONTHEIMPORTANTPARTSANDNOTWORRYABOUTTHEOTHERSTYPICALLYTHEOTHERSARECHECKINGTHESYSTEMANDUPDATINGTHECURRENTANDTIMERVALUESSTEP1CHECKINPUTSTATUSFIRSTTHEPLCTAKESALOOKATEACHINPUTTODETERMINEIFITISONOROFFINOTHERWORDS,ISTHESENSORCONNECTEDTOTHEFIRSTINPUTONHOWABOUTTHESECONDINPUTHOWABOUTTHETHIRDITRECORDSTHISDATAINTOITSMEMORYTOBEUSEDDURINGTHENEXTSTEPSTEP2EXECUTEPROGRAMNEXTTHEPLCEXECUTESYOURPROGRAMONEINSTRUCTIONATATIMEMAYBEYOURPROGRAMSAIDTHATIFTHEFIRSTINPUTWASONTHENITSHOULDTURNONTHEFIRSTOUTPUTSINCEISALREADYKNOWSWHICHINPUTSAREON/OFFFROMTHEPREVIOUSSTEP,ITWILLBEABLETODECIDEWHETHERTHEFIRSTOUTPUTSHOULDBETURNEDONBASEDONTHESTATEOFTHEFIRSTINPUTITWILLSTORETHEEXECUTIONRESULTSFORUSELATERDURINGTHENEXTSTEPSTEP3UPDATEOUTPUTSTSTUSFINALLYTHEPLCUPDATESTHESTATUSOFOUTPUTSITUPDATESTHEOUTPUTSBASEDONWHICHINPUTSWEREONDURINGTHEFIRSTSTEPANDTHERESULTSOFEXECUTINGYOURPROGRAMDURINGTHESECONDSTEPBASEDONTHEEXAMPLEINSTEP2ITWOULDNOWTURNONTHEFIRSTOUTPUTBECAUSETHEFIRSTINPUTWASONANDYOURPROGRAMSAIDTOTURNONTHEFIRSTOUTPUTWHENTHISCONDITIONISTRUEAFTERTHETHIRDSTEPTHEPLCGOESBACKTOSTEPONEANDREPEATSTHESTEPSCONTINUOUSLYONESCANTIMEISDEFINEDASTHETIMEISTAKESTOEXECUTETHE3STEPSLISTEDABOVETHUSAPRACTICALSYSTEMISCONTROLLEDTOPERFORMSPECIFIEDOPERATIONSASDESIREDTHEAT89S52ISALOWPOWER,HIGHPERFORMANCECMOS8BITMICROCONTROLLERWITH8KBYTESOFINSYSTEMPROGRAMMABLEFLASHMEMORYTHEDEVICEISMANUFACTUREDUSINGATMEL’SHIGHDENSITYNONVOLATILEMEMORYTECHNOLOGYANDISCOMPATIBLEWITHTHEINDUSTRYSTANDARD80C51INSTRUCTIONSETANDPINOUTTHEONCHIPFLASHALLOWSTHEPROGRAMMEMORYTOBEREPROGRAMMEDINSYSTEMORBYACONVENTIONALNONVOLATILEMEMORYPROGRAMMERBYCOMBININGAVERSATILE8BITCPUWITHINSYSTEMPROGRAMMABLEFLASHONAMONOLITHICCHIP,THEATMELAT89S52ISAPOWERFULMICROCONTROLLERWHICHPROVIDESAHIGHLYFLEXIBLEANDCOSTEFFECTIVESOLUTIONTOMANYEMBEDDEDCONTROLAPPLICATIONSTHEAT89S52PROVIDESTHEFOLLOWINGSTANDARDFEATURES8KBYTESOFFLASH,256BYTESOFRAM,32I/OLINES,WATCHDOGTIMER,TWODATAPOINTERS,THREE16BITTIMER/COUNTERS,ASIXVECTORTWOLEVELINTERRUPTARCHITECTURE,AFULLDUPLEXSERIALPORT,ONCHIPOSCILLATOR,ANDCLOCKCIRCUITRYINADDITION,THEAT89S52ISDESIGNEDWITHSTATICLOGICFOROPERATIONDOWNTOZEROFREQUENCYANDSUPPORTSTWOSOFTWARESELECTABLEPOWERSAVINGMODESTHEIDLEMODESTOPSTHECPUWHILEALLOWINGTHERAM,TIMER/COUNTERS,SERIALPORT,ANDINTERRUPTSYSTEMTOCONTINUEFUNCTIONINGTHEPOWERDOWNMODESAVESTHERAMCONTENTSBUTFREEZESTHEOSCILLATOR,DISABLINGALLOTHERCHIPFUNCTIONSUNTILTHENEXTINTERRUPTORHARDWARERESETPORT0ISAN8BITOPENDRAINBIDIRECTIONALI/OPORTASANOUTPUTPORT,EACHPINCANSINKEIGHTTTLINPUTSWHENISWRITTENTOPORT0PINS,THEPINSCANBEUSEDASHIGHIMPEDANCEINPUTSPORT0CANALSOBECONFIGUREDTOBETHEMULTIPLEXEDLOWEREDADDRESS/DATABUSDURINGACCESSESTOEXTERNALPROGRAMANDDATAMEMORYINTHISMODE,P0HASINTERNALPULLUPSPORT0ALSORECEIVESTHECODEBYTESDURINGFLASHPROGRAMMINGANDOUTPUTSTHECODEBYTESDURINGPROGRAMVERIFICATIONEXTERNALPULLUPSAREREQUIREDDURINGPROGRAMVERIFICATIONPORT1ISAN8BITBIDIRECTIONALI/OPORTWITHINTERNALPULLUPSTHEPORT1OUTPUTBUFFERSCANSINK/SOURCEFOURTTLINPUTSWHEN1SAREWRITTENTOPORT1PINS,THEYAREPULLEDHIGHBYTHEINTERNALPULLUPSANDCANBEUSEDASINPUTSASINPUTS,PORT1PINSTHATAREEXTERNALLYBEINGPULLEDLOWWILLSOURCECURRENTIILBECAUSEOFTHEINTERNALPULLUPSINADDITION,P10ANDP11CANBECONFIGUREDTOBETHETIMER/COUNTER2EXTERNALCOUNTINPUTP10/T2ANDTHETIMER/COUNTER2TRIGGERINPUTP11/T2EX

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