spi wishbone controller.PDF

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1、SPIWISHBONEControllerJanuary2011ReferenceDesignRD1044IntroductionTheSerialPeripheralInterface(SPI)busprovidesanindustrystandardinterfacebetweenmicroprocessorsandotherdevicesasshowninFigure1.ThisreferencedesigndocumentsaSPIWISHBONEcontrollerdesignedtoprovideaninterfac

2、ebetweenamicroprocessorwithaWISHBONEbusandexternalSPIdevices.Inmastermode,theSPIcontrollercanbeconfiguredforcommunicationwithmultipleoff-chipSPIports.Inslavemode,theSPIsup-portscommunicationswithanoff-chipSPImaster.Asasimpleserialport,theSPIusesfewFPGAresources(seeTa

3、ble6)andlittleboardspaceforwires.ThisSPIreferencedesignusesonlythreepins(clock,datain,anddataout)plusoneselectforeachslavedevice.ASPIisagoodchoiceforcommunicatingwithlow-speeddevicesthatareaccessedintermittentlyandtransferdatastreamsratherthanreadingandwritingtospeci

4、ficaddresses.ASPIisanespeciallygoodchoiceifyoucantakeadvantageofitsfull-duplexnature,whichsendsandreceivesdataatthesametime.Figure1.UsingtheSPIWISHBONEControllertoConnecttoPeripheralsFPGAPeripheralSlaveSPISPIWISHBONEMicroprocessorController(MasterMode)PeripheralWISHB

5、ONESlaveSPIBothVerilogandVHDLversionsofthereferencedesignareavailable.Latticedesigntoolsareusedforsynthesis,placeandrouteandsimulation.ThedesigncanbetargetedtomultipleLatticedevicefamilies.ItssmallsizemakesitportableacrossdifferentFPGAorCPLDarchitectures.Thisdesignas

6、sumestheuserhasexperiencewithWISHBONEcontrollers.InformationavailableinthedocumentslistedintheReferencessectionisnotrepeatedinthisdocument.TheoryofOperationOverviewThisSPIWISHBONEcontrollerprovidesaninterfacebetweenamicroprocessorwithaWISHBONEbusandaSPIdevice.Thecont

7、rollercaneitheractastheSPIMasterorSPISlavedevice.TheselectionoftheMasterorSlavemodeisdoneusingparametersintheHDLcode.Thedesignusesasinglemodule.TheSPIWISHBONEreferencedesignprovidesstandard,fully-configurableSPIportsincluding:•WISHBONEB.3interface•Slaveandmastermodes

8、.Mastermodecancontroluptoeightslaves.Morecanbeaddedifdesired.•Interruptrequesttotheprocessor,configurableforavarietyofstatusconditi