自动化专业外文文献英文文献外文翻译plc方面.docx

自动化专业外文文献英文文献外文翻译plc方面.docx

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自动化专业外文文献英文文献外文翻译plc方面

1、外文原文（复印件）

A：

FundamentalsofSingle—chipMicrocomputer

Thesingle-chipmicrocomputeristheculminationofboththedevelopmentofthedigitalcomputerandtheintegratedcircuitarguablythetowmostsignificantinventionsofthe20thcentury［1].

Thesetowtypesofarchitecturearefoundinsingle—chipmicrocomputer.Someemploythesplitprogram/datamemoryoftheHarvardarchitecture，showninFig.3—5A—1，othersfollowthephilosophy，widelyadaptedforgeneral—purposecomputersandmicroprocessors,ofmakingnologicaldistinctionbetweenprogramanddatamemoryasinthePrincetonarchitecture,showninFig.3-5A—2.

Ingeneraltermsasingle-chipmicrocomputerischaracterizedbytheincorporationofalltheunitsofacomputerintoasingledevice，asshowninFig3—5A-3。

Fig.3-5A-1AHarvardtype

Fig。

3-5A—2。

AconventionalPrincetoncomputer

Reset

Interrupts

Power

Fig3—5A-3。

Principalfeaturesofamicrocomputer

Randomaccessmemory（RAM）.RAMisforthestorageofworkingvariablesanddatausedduringprogramexecution.Thesizeofthismemoryvarieswithdevicetypebutithasthesamecharacteristicwidth（4，8，16bitsetc.）astheprocessor，Specialfunctionregisters，suchasstackpointerortimerregisterareoftenlogicallyincorporatedintotheRAMarea.ItisalsocommoninHarardtypemicrocomputerstotreattheRAMareaasacollectionofregister;itisunnecessarytomakedistinctionbetweenRAMandprocessorregisterasisdoneinthecaseofamicroprocessorsystemsinceRAMandregistersarenotusuallyphysicallyseparatedinamicrocomputer。

Centralprocessingunit（CPU）。

TheCPUismuchlikethatofanymicroprocessor。

Manyapplicationsofmicrocomputersandmicrocontrollersinvolvethehandlingofbinary—codeddecimal（BCD）data（fornumericaldisplays,forexample），henceitiscommontofindthattheCPUiswelladaptedtohandlingthistypeofdata.Itisalsocommontofindgoodfacilitiesfortesting,settingandresettingindividualbitsofmemoryorI/Osincemanycontrollerapplicationsinvolvetheturningonandoffofsingleoutputlinesorthereadingthesingleline。

Theselinesarereadilyinterfacedtotwo—statedevicessuchasswitches,thermostats，solid-staterelays，valves，motor,etc。

Parallelinput/output。

Parallelinputandoutputschemesvarysomewhatindifferentmicrocomputer;inmostamechanismisprovidedtoatleastallowsomeflexibilityofchoosingwhichpinsareoutputsandwhichareinputs.Thismayapplytoallorsomeoftheports.SomeI/Olinesaresuitablefordirectinterfacingto,forexample，fluorescentdisplays，orcanprovidesufficientcurrenttomakeinterfacingothercomponentsstraightforward。

SomedevicesallowanI/Oporttobeconfiguredasasystembustoallowoff—chipmemoryandI/Oexpansion。

Thisfacilityispotentiallyusefulasaproductrangedevelops,sincesuccessiveenhancementsmaybecometoobigforon-chipmemoryanditisundesirablenottobuildontheexistingsoftwarebase.

Serialinput/output.Serialcommunicationwithterminaldevicesiscommonmeansofprovidingalinkusingasmallnumberoflines.Thissortofcommunicationcanalsobeexploitedforinterfacingspecialfunctionchipsorlinkingseveralmicrocomputerstogether。

Boththecommonasynchronoussynchronouscommunicationschemesrequireprotocolsthatprovideframing（startandstop）information.ThiscanbeimplementedasahardwarefacilityorU（S）ART（Universal（synchronous）asynchronousreceiver/transmitter）relievingtheprocessor（andtheapplicationsprogrammer）ofthislow-level,time—consuming，detail。

tismerelynecessarytoselectedabaud—rateandpossiblyotheroptions（numberofstopbits，parity，etc。

）andload（orreadfrom）theserialtransmitter（orreceiver）buffer.Serializationofthedataintheappropriateformatisthenhandledbythehardwarecircuit。

Timing/counterfacilities。

Manyapplicationofsingle-chipmicrocomputersrequireaccurateevaluationofelapsedrealtime。

Thiscanbedeterminedbycarefulassessmentoftheexecutiontimeofeachbranchinaprogrambutthisrapidlybecomesinefficientforallbutsimplestprograms.Thepreferredapproachistousetimercircuitthatcanindependentlycountprecisetimeincrementsandgenerateaninterruptafterapresettimehaselapsed.Thistypeoftimerisusuallyarrangedtobereloadablewiththerequiredcount.Thetimerthendecrementsthisvalueproducinganinterruptorsettingaflagwhenthecounterreacheszero.Bettertimersthenhavetheabilitytoautomaticallyreloadtheinitialcountvalue.Thisrelievestheprogrammeroftheresponsibilityofreloadingthecounterandassessingelapsedtimebeforethetimerrestarted，whichotherwisewoundbenecessaryifcontinuouspreciselytimedinterruptswererequired（asinaclock,forexample）。

Sometimesassociatedwithtimerisaneventcounter.Withthisfacilitythereisusuallyaspecialinputpin,thatcandrivethecounterdirectly。

Timingcomponents.Theclockcircuitryofmostmicrocomputersrequiresonlysimpletimingcomponents.Ifmaximumperformanceisrequired,acrystalmustbeusedtoensurethemaximumclockfrequencyisapproachedbutnotexceeded。

Manyclockcircuitsalsoworkwitharesistorandcapacitoraslow-costtimingcomponentsorcanbedrivenfromanexternalsource。

Thislatterarrangementisusefulisexternalsynchronizationofthemicrocomputerisrequired。

WORDSANDTERMS

culminationn。

顶点

spiltadj.分离的

volatilen。

易变的

commitv.保证

albeitconj.虽然

customadj。

定制的

variantadj。

不同的

piggy-backadj.背负式的

socketn.插座

B：

PLC[1］

PLCs（programmablelogicalcontroller）faceevermorecomplexchallengesthesedays.Whereoncetheyquietlyreplacedrelaysandgaveanoccasionalreporttoacorporatemainframe，theyarenowgroupedintocells,givennewjobandnewlanguages，andareforcedtocompeteagainstagrowingarrayofcontrolproducts.Forthisyear'sannualPLCtechnologyupdate,wequeriedPLCmakersonthesetopicsandmore。

Programminglanguages

HigherlevelPLCprogramminglanguageshavebeenaroundforsometime,butlatelytheirpopularityhasmushrooming。

"AsRaymondLeveille,vicepresident&generalmanager,SiemensEnergy＆Automation.inc；Programmablecontrolsarebeingusedformoreandmoresophisticatedoperations,languagesotherthanladderlogicbecomemorepractical，efficient，andpowerful。

Forexample,it'sverydifficulttowriteatrigonometricfunctionusingladderlogic。

"LanguagesgainingacceptanceincludeBoolean，controlsystemflowcharting,andsuchfunctionchartlanguagesasGraphcetanditsvariation.Andthere’sincreasinginterestinlanguageslikeCandBASIC。

PLCsinprocesscontrol

Thusfar,PLCshavenotbeenusedextensivelyforcontinuousprocesscontrol.Willthiscontinue？

"ThefeelingthatI’vegotten,"saysKenJannotta,manger，productplanning,seriesOneandSeriesSixproduct，atGEFanucNorthAmerica,'isthatPLCswillbeusedintheprocessindustrybutnotnecessarilyforprocesscontrol.”

Severalvendors—obviouslybettingthattheoppositewillhappen—haveintroducedPLCsoptimizedforprocessapplication.RichRyan,manger，commercialmarketing，Allen—bradleyProgrammableControlsDiv。

，citesPLCs’sincreasingusesuchindustriesasfood,chemicals,andpetroleum。

Ryanfeelstherearetwotypesofapplicationsinwhichthey'reappropriate.”one,"hesays，”iswherethesizeoftheprocesscontrolsystemthat’sbeingautomateddoesn'tjustifyDCS［distributedcontrolsystem]。

Withthestartingpricetagsofchoseproductsbeingrelativelyhigh,aprogrammablecontrollermakessenseforsmall,lowloopcountapplication。

Thesecondiswhereyouhavetointegratetheloopcloselywiththesequentiallogical。

Batchcontrollersareprimeexample，wherethesequenceandmaintainingtheprocessvariableareintertwinedsocloselythatthebenefitsofhavingaprogrammablecontrollertodothesequentiallogicaloutweighssomeofthedisadvantagesofnothavingadistributedcontrolsystem.”

BillBarkovitz,presidentofTriconex，predictsthat"allfuturecontrollersthatcomeoutintheprocesscontrolsystembusinesswillembracealotofmorePLCtechnologyandalotmorePLCfunctionalitythantheyeverdidbefore。

"

CommunicationsandMAP

Communicationsarevitaltoanindividualautomationcellandtobeautomatedfactoryasawhole.We’veheardalotaboutMAPinthelastfewyears，andalotofcompanieshavejumpedonthebandwagon。

［2］Many，however,weredisappointedwhenafully-definedandcompletedMAPspecificationdidn’tappearimmediately.SaysLarryKomarek：

”Rightnow,MAPisstillamovingtargetforthemanufacturers，aspecificationthatisnotfinal.Presently,forexample。

peopleareintroducingproductstomeettheMAP2。

1standard。

Yet2.1—basedproductswillbeobsoletewhenthenewstandardforMAP3.0isintroduced.”

Becauseofthis,manyPLCvendorsareholdingoffonfullMAPimplementations。

Omron,forexample，hasanongoingMAP-compatibilityprogram；［3］butFrankNewburn,vicepresidentofOmron'sIndustrialDivision，reportsthatbecauseofthelackofafirmdefinition,Omron’sPLCsdon’tyettalktoMAP.

Sinceit’sunlikelythatanindividualPLCwouldtalktobroadMAPanyway，makersareconcentratingonproprietarynetworks。

AccordingtoSalProvanzano,usersfearthatiftheydogetonboardandvendorswithdrawfromMAP，they'llbetheonesleftholdingacommunicationsstructurethat’snotsupported.

UniversalI/O

WhilethereareconcernsaboutthelackofcompatiblecommunicationsbetweenPLCsfromdifferentvendors,theconnectionattheotherend—theI/O—isevenmorefragmented。

Withrareexceptions,I/Oisstillproprietary。

YettherearethosewhofeelthatI/Owilleventuallybecomemoreuniversal.GEFanucishopin