电气工程及其自动化专业-外文文献-英文文献-外文翻译-plc方面

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1、1、外文原文A:FundamentaIsofSingIe-chipMicrocomputerThesingle~chipmicrocomputeristheculminationofboththedevelopmentofthedigitalcomputerandtheintegratedcircuitarguab1ythetowmostsignificantinventionsofthe20thcentury[1].Thesetowtypesofarchitecturearefoundinsingle-chipmicrocomputer.Some

2、emp1oythesplitprogram/datamemoryoftheHarvardarchitecture,showninFig.3-5A-1,othersfoilowthephi1osophy,widelyadaptedforgeneral-purposecomputersandmicroprocessors,ofmakingnologicaldistinctionbetweenprogramanddatamemoryasinthePrincetonarchitccturc,showninFig.3-5A-2・Ingeneraltermsa

3、single~chipmicrocomputerischaracterizedbytheincorporationofalltheunitsofacomputerintoasing1edevice,asshowninFig3-5A-3.Fig.3-5A-1AHarvardtypeFig.3・5A・2.AconventionalPrincetoncomputerReadonIymemory(ROM)・ROMisusuallyforthepermanent,non-volatilestorageofanapp1icationsprogram.Manym

4、icrocomputersandinareintendedforhigh-volumeapp1icationsandhencetheeconomicalmanufactureofthedevicesrequiresthatthecontentsoftheprogrammemorybecommittedpermanentlyduringthemanufactureofchips.Clearly,thisimp1iesarigorousapproachtoROMcodedeve1opmentsincechangescannotbemadeafterma

5、nufacturc.Thisdevelopmentprocessmayinvolveemu1ationusingasophisticateddevelopmentsystemwithahardwareemu1ationcapabilityaswellastheuseofpowerfulsoftwaretools.SomemanufacturersprovideadditionalROMoptionsbyincludingintheirrangedeviceswith(orintendedforusewith)userprogrammab1ememo

6、ry.Thesimplestoftheseisusuallydevicewhichcanoperateinamicroprocessormodebyusingsomeoftheinput/outputlinesasanaddressanddatabusforaccessingexternalmemory.ThistypeofdevicecanbehavefunctionallyasthesinglechipmicrocomputerfromwhichitisderivedalbeitwithrestrictedI/Oandamodifiedexte

7、rnalcircuit.Theuseofthesedevicesiscommoneveninproductioncircuitswherethevolumedoesnotjustifythedevelopmentcostsofcustomon-chipROM[2];therecanstillbeasignificantsavinginI/Oandotherchipscomparedtoaconventionalmicroprocessorbasedcircuit.MorcexactreplacementforROMdevicescanbeobtai

8、nedintheformofvariantswith'piggy-back'EPROM(Erasab1eprogramma