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1、英文资料及中文翻译PDIUSBD12----USBinterfacedevicewithparallelbusThePDIUSBD12isacostandfeatureoptimizedUSBdevice.Itisnormallyusedinmicrocontrollerbasedsystemsandcommunicateswiththesystemmicrocontrolleroverthehigh-speedgeneralpurposeparallelinterface.ItalsosupportslocalDMAtransfer.Thi
2、smodularapproachtoimplementingaUSBinterfaceallowsthedesignertochoosetheoptimumsystemmicrocontrollerfromtheavailablewidevariety.Thisflexibilitycutsdownthedevelopmenttime,risks,andcostsbyallowingtheuseoftheexistingarchitectureandminimizefirmwareinvestments.Thisresultsinthefas
3、testwaytodevelopthemostcosteffectiveUSBperipheralsolution.ThePDIUSBD12fullyconformstotheUSBspecificationRev.2.0(basicspeed).Itisalsodesignedtobecompliantwithmostdeviceclassspecifications:ImagingClass,MassStorageDevices,CommunicationDevices,PrintingDevices,andHumanInterfaceD
4、evices.Assuch,thePDIUSBD12isideallysuitedformanyperipheralslikePrinter,Scanner,ExternalMassStorage(ZipDrive),DigitalStillCamera,etc.ItoffersanimmediatecostreductionforapplicationsthatcurrentlyuseSCSIimplementations.ThePDIUSBD12lowsuspendpowerconsumptionalongwiththeLazyClock
5、outputallowsforeasyimplementationofequipmentthatiscomplianttotheACPI(TM),OnNOW(TM),andUSBpowermanagementrequirements.Thelowoperatingpowerallowstheimplementationofbuspoweredperipherals.Inaddition;italsoincorporatesfeatureslikeSoftConnect(TM),GoodLink(TM),programmableclockout
6、put,lowfrequencycrystaloscillator,andintegrationofterminationresistors.AllofthesefeaturescontributetosignificantcostsavingsinthesystemimplementationandatthesametimeeasetheimplementationofadvancedUSBfunctionalityintotheperipherals.1.DMAtransferDirectMemoryAddress(DMA)allowsa
7、nefficienttransferofablockofdatabetweenthehostandlocalsharedmemory.UsingaDMAcontroller,datatransferbetweenthePDIUSBD12’smainendpoint(endpoint2)andlocalsharedmemorycanhappenautonomouslywithoutlocalCPUintervention.PrecedinganyDMAtransfer,thelocalCPUreceivesfromthehosttheneces
8、sarysetupinformationandprogramstheDMAcontrolleraccordingly.Typically,theDMAcontrol
