英文資料翻譯機(jī)0405-33張明旺TheS7-200seriesisalineofmicro-programmablelogiccontrollers(MicroPLC)thatcancontrolavarietyofautomationapplications.Compactdesign,lowcost,andapowerfulinstructionsetmaketheS7-200aperfectsolutionforcontrollingsmallapplications.ThewidevarietyofS7-200modelsandtheWindows-basedprogrammingtoolgiveyoutheflexibilityyouneedtosolveyourautomationproblems.TheS7-200seriesofmicro-programmablelogiccontrollers(MicroPLC)cancontrolawidevarietyofdevicestosupportyourautomationneeds.TheS7-200monitorsinputsandchangesoutputsascontrolledbytheuserprogram,whichcanincludeBooleanlogic,counting,timing,complexmathoperations,andcommunicationswithotherintelligentdevices.Thecompactdesign,flexibleconfiguration,andpowerfulinstructionsetcombinetomaketheS7-200aperfectsolutionforcontrollingawidevarietyofapplications.TheS7-200storesinformationindifferentmemorylocationsthathaveuniqueaddresses.Youcanexplicitlyidentifythememoryaddressthatyouwanttoaccess.Thisallowsyourprogramtohavedirectaccesstotheinformation.Table4-1showstherangeofintegervaluesthatcanberepresentedbythedifferentsizesofdata.Table4-1DecimalandHexadecimalRangesfortheDifferentSizesofDataRepresentationByte(B)Word(W)DoubleWord(D)UnsignedInteger0to2550toFF0to65,5350toFFFF0to4,294,967,2950toFFFFFFFFSignedInteger-128to+12780to7F-32,768to+32,7678000to7FFF-2,147,483,648to+2,147,483,64780000000to7FFFFFFFRealIEEE32-bitFloatingPointNotapplicableNotapplicable+1.175495E-38to+3.402823E+38(positive)-1.175495E-38to-3.402823E+38(negative)Toaccessabitinamemoryarea,youspecifytheaddress,whichincludesthememoryareaidentifier,thebyteaddress,andthebitnumber.Figure4-3showsanexampleofaccessingabit(whichisalsocalled“byte.bit”addressing).Inthisexample,thememoryareaandbyteaddress(I=input,and3=byte3)arefollowedbyaperiod(“.”)toseparatethebitaddress(bit4).Youcanaccessdatainmostmemoryareas(V,I,Q,M,S,L,andSM)asbytes,words,ordoublewordsbyusingthebyte-addressformat.Toaccessabyte,word,ordoublewordofdatainthememory,youmustspecifytheaddressinawaysimilartospecifyingtheaddressforabit.Thisincludesanareaidentifier,datasizedesignation,andthestartingbyteaddressofthebyte,word,ordouble-wordvalue,asshowninFigure4-4.Datainothermemoryareas(suchasT,C,HC,andtheaccumulators)areaccessedbyusinganaddressformatthatincludesanareaidentifierandadevicenumber.AccessingDataintheMemoryAreasProcess-ImageInputRegister:ITheS7-200samplesthephysicalinputpointsatthebeginningofeachscancycleandwritesthesevaluestotheprocess-imageinputregister.Youcanaccesstheprocess-imageinputregisterinbits,bytes,words,ordoublewords:Bit:Ibyteaddress.bitaddressI0.1Byte,Word,orDoubleWord:IsizestartingbyteaddressIB4Process-ImageOutputRegister:QAttheendofthescancycle,theS7-200copiesthevaluesstoredintheprocess-imageoutputregistertothephysicaloutputpoints.Youcanaccesstheprocess-imageoutputregisterinbits,bytes,words,ordoublewords:Bit:Qbyteaddress.bitaddressQ1.1Byte,Word,orDoubleWord:QsizestartingbyteaddressQB5VariableMemoryArea:VYoucanuseVmemorytostoreintermediateresultsofoperationsbeingperformedbythecontrollogicinyourprogram.YoucanalsouseVmemorytostoreotherdatapertainingtoyourprocessortask.YoucanaccesstheVmemoryareainbits,bytes,words,ordoublewords:Bit:Vbyteaddress.bitaddressV10.2Byte,Word,orDoubleWord:VsizestartingbyteaddressVW100BitMemoryArea:MYoucanusethebitmemoryarea(Mmemory)ascontrolrelaystostoretheintermediatestatusofanoperationorothercontrolinformation.Youcanaccessthebitmemoryareainbits,bytes,words,ordoublewords:Bit:Mbyteaddress.bitaddressM26.7Byte,Word,orDoubleWord:MsizestartingbyteaddressMD20TimerMemoryArea:TTheS7-200providestimersthatcountincrementsoftimeinresolutions(time-baseincrements)of1ms,10ms,or100ms.Twovariablesareassociatedwithatimer:-Currentvalue:this16-bitsignedintegerstorestheamountoftimecountedbythetimer.-Timerbit:thisbitissetorclearedasaresultofcomparingthecurrentandthepresetvalue.Thepresetvalueisenteredaspartofthetimerinstruction.Youaccessbothofthesevariablesbyusingthetimeraddress(T+timernumber).Accesstoeitherthetimerbitorthecurrentvalueisdependentontheinstructionused:instructionswithbitoperandsaccessthetimerbit,whileinstructionswithwordoperandsaccessthecurrentvalue.AsshowninFigure4-5,theNormallyOpenContactinstructionaccessesthetimerbit,whiletheMoveWordinstructionaccessesthecurrentvalueofthetimer.Format:TtimernumberT24CounterMemoryArea:CTheS7-200providesthreetypesofcountersthatcounteachlow-to-hightransitioneventonthecounterinput(s):onetypecountsuponly,onetypecountsdownonly,andonetypecountsbothupanddown.Twovariablesareassociatedwithacounter:-Currentvalue:this16-bitsignedintegerstorestheaccumulatedcount.-Counterbit:thisbitissetorclearedasaresultofcomparingthecurrentandthepresetvalue.Thepresetvalueisenteredaspartofthecounterinstruction.Youaccessbothofthesevariablesbyusingthecounteraddress(C+counternumber).Accesstoeitherthecounterbitorthecurrentvalueisdependentontheinstructionused:instructionswithbitoperandsaccessthecounterbit,whileinstructionswithwordoperandsaccessthecurrentvalue.AsshowninFigure4-6,theNormallyOpenContactinstructionaccessesthecounterbit,whiletheMoveWordinstructionaccessesthecurrentvalueofthecounter.Format:CcounternumberC24Accumulators:ACTheaccumulatorsareread/writedevicesthatcanbeusedlikememory.Forexample,youcanuseaccumulatorstopassparameterstoandfromsubroutinesandtostoreintermediatevaluesusedinacalculation.TheS7-200providesfour32-bitaccumulators(AC0,AC1,AC2,andAC3).Youcanaccessthedataintheaccumulatorsasbytes,words,ordoublewords.Thesizeofthedatabeingaccessedisdeterminedbytheinstructionthatisusedtoaccesstheaccumulator.AsshowninFigure4-7,youusetheleastsignificant8or16bitsofthevaluethatisstoredintheaccumulatortoaccesstheaccumulatorasbytesorwords.Toaccesstheaccumulatorasadoubleword,youuseall32bits.Format:ACaccumulatornumberAC0SpecialMemory:SMTheSMbitsprovideameansforcommunicatinginformationbetweentheCPUandyourprogram.YoucanusethesebitstoselectandcontrolsomeofthespecialfunctionsoftheS7-200CPU,suchas:abitthatturnsonforthefirstscancycle,abitthattogglesatafixedrate,orabitthatshowsthestatusofmathoroperationalinstructions.(FormoreinformationabouttheSMbits,seeAppendixD.)YoucanaccesstheSMbitsasbits,bytes,words,ordoublewords:Bit:SMbyteaddress.bitaddressSM0.1Byte,Word,orDoubleWord:SMsizestartingbyteaddressSMB86LocalMemoryArea:LTheS7-200provides64bytesoflocalmemoryofwhich60canbeusedasscratchpadmemoryorforpassingformalparameterstosubroutines.Tip:IfyouareprogrammingineitherLADorFBD,STEP7-Micro/WINreservesthelastfourbytesof