3-電氣工程及其自動化專業(yè)-外文文獻-英文文獻-外文翻譯-plc方面

外文原文（復(fù)印件）A:FundamentalsofSingle-chipMicrocomputerThesingle-chipmicrocomputeristheculminationofboththedevelopmentofthedigitalcomputerandtheintegratedcircuitarguablythetowmostsignificantinventionsofthe20thcentury[1].Thesetowtypesofarchitecturearefoundinsingle-chipmicrocomputer.Someemploythesplitprogram/datamemoryoftheHarvardarchitecture,showninFig.3-5A-1,othersfollowthephilosophy,widelyadaptedforgeneral-purposecomputersandmicroprocessors,ofmakingnologicaldistinctionbetweenprogramanddatamemoryasinthePrincetonarchitecture,showninFig.3-5A-2.Ingeneraltermsasingle-chipmicrocomputerischaracterizedbytheincorporationofalltheunitsofacomputerintoasingledevice,asshowninFig3-5A-3.ProgramProgrammemoryInput&OutputInput&OutputunitCPUCPUDatamemoryDatamemoryFig.3-5A-1AInput&Input&OutputunitCPUCPUmemorymemoryFig.3-5A-2.AconventionalPrincetoncomputerTimer/CounterSystemclockTimer/CounterSystemclockExternalTimingcomponentsSerialI/OSerialI/OROMROMResetPrarallelI/OPrarallelI/ORAMInterruptsRAMCPUCPUPowerFig3-5A-3.PrincipalfeaturesofamicrocomputerReadonlymemory(ROM).ROMisusuallyforthepermanent,non-volatilestorageofanapplicationsprogram.Manymicrocomputersandmicrocontrollersareintendedforhigh-volumeapplicationsandhencetheeconomicalmanufactureofthedevicesrequiresthatthecontentsoftheprogrammemorybecommittedpermanentlyduringthemanufactureofchips.Clearly,thisimpliesarigorousapproachtoROMcodedevelopmentsincechangescannotbemadeaftermanufacture.Thisdevelopmentprocessmayinvolveemulationusingasophisticateddevelopmentsystemwithahardwareemulationcapabilityaswellastheuseofpowerfulsoftwaretools.SomemanufacturersprovideadditionalROMoptionsbyincludingintheirrangedeviceswith(orintendedforusewith)userprogrammablememory.Thesimplestoftheseisusuallydevicewhichcanoperateinamicroprocessormodebyusingsomeoftheinput/outputlinesasanaddressanddatabusforaccessingexternalmemory.ThistypeofdevicecanbehavefunctionallyasthesinglechipmicrocomputerfromwhichitisderivedalbeitwithrestrictedI/Oandamodifiedexternalcircuit.TheuseoftheseROMlessdevicesiscommoneveninproductioncircuitswherethevolumedoesnotjustifythedevelopmentcostsofcustomon-chipROM[2];therecanstillbeasignificantsavinginI/Oandotherchipscomparedtoaconventionalmicroprocessorbasedcircuit.MoreexactreplacementforROMdevicescanbeobtainedintheformofvariantswith'piggy-back'EPROM(ErasableprogrammableROM)socketsordeviceswithEPROMinsteadofROM。ThesedevicesarenaturallymoreexpensivethanequivalentROMdevice,butdoprovidecompletecircuitequivalents.EPROMbaseddevicesarealsoextremelyattractiveforlow-volumeapplicationswheretheyprovidetheadvantagesofasingle-chipdevice,intermsofon-chipI/O,etc.,withtheconvenienceofflexibleuserprogrammability.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.WORDSANDTERMSculminationn.頂點spiltadj.分別的volatilen.易變的commitv.保證albeitconj.雖然customadj.定制的variantadj.不同的piggy-backadj.背負式的socketn.插座B:PLC[1]PLCs(programmablelogicalcontroller)faceevermorecomplexchallengesthesedays.Whereoncetheyquietlyreplacedrelaysandgaveanoccasionalreporttoacorporatemainframe,theyarenowgroupedintocells,givennewjobandnewlanguages,andareforcedtocompeteagainstagrowingarrayofcontrolproducts.Forthisyear'sannualPLCtechnologyupdate,wequeriedPLCmakersonthesetopicsandmore.ProgramminglanguagesHigherlevelPLCprogramminglanguageshavebeenaroundforsometime,butlatelytheirpopularityhasmushrooming."AsRaymondLeveille,vicepresident&generalmanager,SiemensEnergy&Automation.inc;Programmablecontrolsarebeingusedformoreandmoresophisticatedoperations,languagesotherthanladderlogicbecomemorepractical,efficient,andpowerful.Forexample,it'sverydifficulttowriteatrigonometricfunctionusingladderlogic."LanguagesgainingacceptanceincludeBoolean,controlsystemflowcharting,andsuchfunctionchartlanguagesasGraphcetanditsvariation.Andthere'sincreasinginterestinlanguageslikeCandBASIC.PLCsinprocesscontrolThusfar,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."CommunicationsandMAPCommunicationsarevitaltoanindividualautomationcellandtobeautomatedfactoryasawhole.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/OWhilethereareconcernsaboutthelackofcompatiblecommunicationsbetweenPLCsfromdifferentvendors,theconnectionattheotherend-theI/O-isevenmorefragmented.Withrareexceptions,I/Oisstillproprietary.YettherearethosewhofeelthatI/Owilleventuallybecomemoreuniversal.GEFanucishopingtodothatwithitsGeniussmartI/Oline.TheindependentI/Omakersarepullinginthesamedirection.ManysaythatI/Oissuchahigh-valueitemthatPLCmakerswillalwayswanttokeepitproprietary.AsKenJannotta,says:"TheI/Oisgoingtobeadisproportionateamountofthehardwaresale.CertainlyeachPLCvendorisgoingtotrytoprotectthat."Forthatreason,hesays,PLCmakerswon'tbeginsellinguniversalI/Osystemfromothervendor."ifwestartsellingthatkindofproduct,"saysjannotta,"whatdowemanufacture?"WithmoreintelligentI/Oappearing,SalProvanzanofeelsthiswillleadtomoredifferentiationamongI/Ofromdifferentmakers."WheretheI/Obecomesextremelyintelligentandbecomespartofthesystem,"hesays,"itreallyishardtodefinewhichistheI/OandwhichisCPU.ItreallyCPU,ifyouwill,isequallyintegratedintothesystemastheI/O."ConnectingPLCI/OtoPCsWhiledifferentPLCsprobablywillcontinuetouseproprietaryI/O,severalvendorsmakeitpossibletoconnect5theirI/OtoIBMPC-compatibleequipment.Alle-bradeley,Could,andCincinnatiMilacronalreadyhave,andrumorhasitthatGEisplanningsomethingalongthesesamelines.[4]BillKetelhut,manageofproductplanningatGEFanucNorthAmerica,seesthissortofthingasalternativetouniversalI/O."Ithinkthetrend,insteadoftowarduniversalI/O,willbemultiplehostinterface,"hesays.JodieGlore,directorofmarking,SquareDAutomationProducts,ViewsitasanotherindicationthatPLCsare,andhavebeenforsometime,industrialcomputers.PLCsVSPCsIftheIBM7552,theActionInstrumentsBC22,andothercomputersareappearingonthefactoryfloor,won'tthismeannewcompetitionforPLCs?RichRyan:"Therearesomecontrolfunctionsthatarebetterjobsforcomputers.Programmablecontrollershavebeenforcedtofitintothoseapplications."Yet,themajorityofvendorswesurveyeddon'tlikethe"PCinvasion"willposeaproblemforthem.MostsaidthatPLCsandPCsareenoughapartinarchitecturethattheywillusuallydothecontrol.Theydon'tfeelthatPCswilltakejobsfromPLCsjustbecausePLCI/OmodulescannowbeconnectedtoPCs;theybelievethissimplymeansthatPLCsandPCswillbeabletosharethesamedata."Thereareinherentarchitecturaldifferencesbetweenageneralpurposecomputer,"saysRichRyan,"andaprogrammablecontroller.Therearehardwareconstructsbuiltintoalmosteverymanufacture'sprogrammablecontrollertodaythatcustomizethehardwaretorunladderlogicandtosolvemachinecode."Onefundamentaldifferencehecitesiscalledstateofthemachine.Ryan:"Whenyoushutthemachineoff,orinterruptthecycle,oryoujumptoanotherspotinthecycle,programmablecontrollersinherentlyrememberthestateofthemachine:whatthetimerswere,whatthecounterswere,whatthestatesofallthelatcheswere.Computersdon'tinherentlydothat."WORDSANDTERMSbetv.確信optimizedn.優(yōu)化程序corporateadj.共同的mushroomv.快速發(fā)展trigonometricfunction三角函數(shù)vendorn.廠商tagn.標簽smartadj.智能型的compatibleadj.兼容的外文資料翻譯譯文單片機基礎(chǔ)單片機是電腦和集成電路發(fā)展的巔峰，有據(jù)可查的是他們也是20世紀最有意義的兩大獨創(chuàng)。這兩種特性在單片機中得到了充分的體現(xiàn)。一些廠家用這兩種特性區(qū)分程序內(nèi)存和數(shù)據(jù)內(nèi)存在硬件中的特性，如圖3-5A-1，依據(jù)同樣的原理廣泛的適用于一般目的的電腦和微電腦，一些廠家在程序內(nèi)存和數(shù)據(jù)內(nèi)存之間不區(qū)分的像Princeton特性，展示如圖3-5A-2.只讀存貯器(ROM).ROM是通常的永久性的，非應(yīng)用程序的易失性存儲器。不少微機和單片機用于大批量應(yīng)用，因此，經(jīng)濟的設(shè)備制造要求的程序存儲器的內(nèi)容是在制造期間永久性的刻錄在芯片中，這意味著嚴謹?shù)姆椒?，因為修改ROM代碼不能制造之后發(fā)展。這一發(fā)展過程可能涉及仿真,運用硬件仿真功能以及強大的軟件工具運用先進的開發(fā)系統(tǒng)。一些制造商在其供應(yīng)的設(shè)備包括的范圍（或擬運用）用戶可編程內(nèi)存.其中最簡潔的通常是設(shè)備能夠運行于微處理器模式通過運用一些輸入/輸出作為地址線額外的ROM選項和數(shù)據(jù)總線訪問外部內(nèi)存.這種類型的設(shè)備可以表現(xiàn)為單芯片微型計算機盡管有限制的I/O和外部修改這些設(shè)備的電路.小內(nèi)存裝置的應(yīng)用是特別普遍的在永久性內(nèi)存的制造中[2];但仍舊可以在我節(jié)約大量成本I/O和其它芯片相比，傳統(tǒng)的基于微處理器電路.更精確的ROM設(shè)備更換，可在與'形式變種背馱式'EPROM（可擦除可編程只讀存儲器）插座或存儲器，而不是ROM器件。這些器件自然價格比同等ROM設(shè)備貴，但不供應(yīng)完整的等效電路.EPROM的設(shè)備也特別有吸引力對于低容量應(yīng)用中，他們供應(yīng)的單芯片器件的優(yōu)勢，在以下方面的板載I/O等，在敏捷的用戶可編程帶來的便利。隨機存取存儲器（RAM）。RAM用于變量和工作在程序運用該存儲器的執(zhí)行.隨數(shù)據(jù)存儲設(shè)備的大小不同類型而有所不同，但具有相同的特征寬度（4,8,16比特等）作為處理器。特別功能寄存器，如棧指針或定時器寄存器，往往邏輯納入內(nèi)存區(qū)域.它也在型微電腦的硬件中做集中內(nèi)存，它是不必要的區(qū)分內(nèi)存和處理器之間的區(qū)分在通常不物理上分開的微機中。中心處理單元（CPU）。CPU是很象微型電子計算機和微限制器的任何微電腦.很多微電腦和微限制器涉及到二進制編碼(十進制處理（BCD）的數(shù)據(jù)為例）數(shù)字顯示，因而，經(jīng)?？梢园l(fā)覺該CPU是很適合處理這種類型的數(shù)據(jù)。對設(shè)施良好與否進行的測試，設(shè)置和重置單個位的內(nèi)存或I/O限制器的應(yīng)用程序，也是常見的因為很多涉及打開和關(guān)閉的單輸出線或在單線.這些線很簡潔連接到二進制的設(shè)備，如開關(guān)，恒溫器，固態(tài)繼電器，閥門，電機等并行輸入/輸出.并行輸入和輸出的支配有所不同，在不同的微機，在大多數(shù)設(shè)立一個機制，至少選擇讓其中一些引腳輸出，一些引腳輸如是特別敏捷的。這可能適用于全部或端口.有些I/O線干脆連接到適當?shù)脑O(shè)備，例如，熒光顯示器，也可以供應(yīng)足夠的電流，使接口和其他設(shè)備干脆相連.一些設(shè)備允許一個I/O端口,其他組件將作為系統(tǒng)總線配置為允許片外存儲器和I/O擴展。這個設(shè)施是潛在有用的一個產(chǎn)品系列的發(fā)展，因為連續(xù)增加可能成為太上存儲器，這是不行取的，不是建立在現(xiàn)有的軟件基礎(chǔ)上的。串行輸入/輸出。串行通信是指與終端設(shè)備的鏈接運用少量的通訊線.這種通訊也可利用特別的接口連接功能芯片使幾個微型機連在一起。雙方共同異步同步通信方案要求的規(guī)則供應(yīng)成幀（啟動和停止）的信息。這可以作為一個硬件設(shè)施或U（擰）藝術(shù)（通用執(zhí)行（同步）異步接收器/發(fā)送器）減輕處理器（和應(yīng)用程序）的這種低層次的確費時.它也只須要選擇一個波特率及其他可能的選擇（停止位，奇偶校驗等）和負載號碼（或讀?。?，串行發(fā)送器（或接收）的緩沖器.進行適當?shù)母袷降臄?shù)據(jù)串行處理，然后由硬件電路完成。定時/計數(shù)器設(shè)施。很多應(yīng)用的單片機須要對過去的真實時間精確的評價。這可以由每個程序中的執(zhí)行時間分支仔細評估，但除最簡潔的程序外，他的工作效率不高。首選方法是運用計時器電路，能獨立計算精確的時間增量，并生成一個預(yù)設(shè)的時間后中斷的時間。這種類型的定時器通常在所要求的數(shù)量可重載中應(yīng)用。計時器然后削減此值產(chǎn)生中斷或設(shè)置標記時，計數(shù)器到達零.更好的計時器有自動加載初始值的功能。這將緩解重新加載計數(shù)器和評估所用的時間，計時器重新啟動之前這是必要的。有時候與定時器相關(guān)的是一個事務(wù)計數(shù)器。這個設(shè)備通常有一個特別的輸入引腳，可干脆驅(qū)動計數(shù)器。定時元件。大多數(shù)微型計算機時鐘電路只須要簡潔的計時元件.假如要求最高性能，必需運用晶體以確保最大時鐘頻率接近，但不會超出。很多時鐘電路，還具有電阻和低電容工作成本定時元件，也可以從外部源驅(qū)動。這后一種支配是有用的在微機外部同步是必需的時候。B:PLC[1]今日的PLC（可編程邏輯限制器）將面對日益困難的挑戰(zhàn)。一旦他們靜靜地取代繼電器，間或向主機報告，假如他們將他們比作細胞，給予新的工作和新的語言，將被迫和大量的限制產(chǎn)品競爭。對于今年的年度PLC技術(shù)的更新，我們對PLC的制造商會就這些主題提出更多問題.編程語言更高水平的PLC編程語言已經(jīng)推行有一段時間了，但最近的流行，如雨后春筍般。正如雷蒙德萊韋耶，副總裁兼總經(jīng)理，西門子能源和自動化公司，可編程限制正在為更困難的操作運用，梯形邏輯比語言變得更加實際，有效和強大的。舉例來說，很難寫三角函數(shù)運用梯形邏輯。“語言