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ID:15372260
大小:82.00 KB
页数:16页
时间:2018-08-02
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1、MicrocomputerSystemsElectronicsystemsareusedforhandinginformationinthemostgeneralsense;thisinformationmaybetelephoneconversation,instrumentreadoracompany’saccounts,butineachcasethesamemaintypeofoperationareinvolved:theprocessing,storageandtransmissionofinformatio
2、n.inconventionalelectronicdesigntheseoperationsarecombinedatthefunctionlevel;forexampleacounter,whetherelectronicormechanical,storesthecurrentandincrementsitbyoneasrequired.Asystemsuchasanelectronicclockwhichemployscountershasitsstorageandprocessingcapabilitiessp
3、readthroughoutthesystembecauseeachcounterisabletostoreandprocessnumbers.Presentdaymicroprocessorbasedsystemsdepartfromthisconventionalapproachbyseparatingthethreefunctionsofprocessing,storage,andtransmissionintodifferentsectionofthesystem.Thispartitioningintothre
4、emainfunctionswasdevisedbyVonNeumannduringthe1940s,andwasnotconceivedespeciallyformicrocomputers.Almosteverycomputerevermadehasbeendesignedwiththisstructure,anddespitetheenormousrangeintheirphysicalforms,theyhaveallbeenofessentiallythesamebasicdesign.Inamicroproc
5、essorbasedsystemtheprocessingwillbeperformedinthemicroprocessoritself.Thestoragewillbebymeansofmemorycircuitsandthecommunicationofinformationintoandoutofthesystemwillbebymeansofspecialinput/output(I/O)circuits.Itwouldbeimpossibletoidentifyaparticularpieceofhardwa
6、rewhichperformedthecountinginamicroprocessorbasedclockbecausethetimewouldbestoredinthememoryandincrementedatregularintervalsbutthemicroprocessor.However,thesoftwarewhichdefinedthesystem’sbehaviorwouldcontainsectionsthatperformedascounters.Theapparentlyratherabstr
7、actapproachtothearchitectureofthemicroprocessoranditsassociatedcircuitsallowsittobeveryflexibleinuse,sincethesystemisdefinedalmostentirelysoftware.Thedesignprocessislargelyoneofsoftwareengineering,andthesimilar16problemsofconstructionandmaintenancewhichoccurincon
8、ventionalengineeringareencounteredwhenproducingsoftware.Thefigure1.1illustrateshowthesethreesectionswithinamicrocomputerareconnectedintermsofthecommunicationof
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