3-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

《3-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》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、1、外文原文（复印件）A:FundamentalsofSingle-chipMicrocomputerThesingle-chipmicrocomputeristheculminationofboththedevelopmentofthedigitalcomputerandtheintegratedcircuitarguablythetowmostsignificantinventionsofthe20thcentury[1].Thesetowtypesofarchitecturearefoundinsingle-chipmicrocom

2、puter.Someemploythesplitprogram/datamemoryoftheHarvardarchitecture,showninFig.3-5A-1,othersfollowthephilosophy,widelyadaptedforgeneral-purposecomputersandmicroprocessors,ofmakingnologicaldistinctionbetweenprogramanddatamemoryasinthePrincetonarchitecture,showninFig.3-5A-2.

3、Ingeneraltermsasingle-chipmicrocomputerischaracterizedbytheincorporationofalltheunitsofacomputerintoasingledevice,asshowninFig3-5A-3.ProgrammemoryInput&OutputunitCPUDatamemoryFig.3-5A-1AHarvardtypeInput&OutputunitCPUmemoryFig.3-5A-2.AconventionalPrincetoncomputerTimer/Cou

4、nterSystemclockExternalTimingcomponentsSerialI/OROMResetPrarallelI/ORAMInterruptsCPUPowerFig3-5A-3.PrincipalfeaturesofamicrocomputerReadonlymemory(ROM).ROMisusuallyforthepermanent,non-volatilestorageofanapplicationsprogram.Manymicrocomputersandmicrocontrollersareintendedf

5、orhigh-volumeapplicationsandhencetheeconomicalmanufactureofthedevicesrequiresthatthecontentsoftheprogrammemorybecommittedpermanentlyduringthemanufactureofchips.Clearly,thisimpliesarigorousapproachtoROMcodedevelopmentsincechangescannotbemadeaftermanufacture.Thisdevelopment

6、processmayinvolveemulationusingasophisticateddevelopmentsystemwithahardwareemulationcapabilityaswellastheuseofpowerfulsoftwaretools.SomemanufacturersprovideadditionalROMoptionsbyincludingintheirrangedeviceswith(orintendedforusewith)userprogrammablememory.Thesimplestofthes

7、eisusuallydevicewhichcanoperateinamicroprocessormodebyusingsomeoftheinput/outputlinesasanaddressanddatabusforaccessingexternalmemory.ThistypeofdevicecanbehavefunctionallyasthesinglechipmicrocomputerfromwhichitisderivedalbeitwithrestrictedI/Oandamodifiedexternalcircuit.The

8、useoftheseROMlessdevicesiscommoneveninproductioncircuitswherethevolumedoesnotjustifythedevelopme