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PRODUCT PREVIEW
4SystemInterconnect
4.1InternalBuses,Bridges,andSwitchFabrics
TMS320C6454
Fixed-PointDigitalSignalProcessor
SPRS311A–APRIL2006–REVISEDDECEMBER2006
OntheC6454device,theC64x+Megamodule,theEDMA3transfercontrollers,andthesystem
peripheralsareinterconnectedthroughtwoswitchfabrics.Theswitchfabricsallowforlow-latency,
concurrentdatatransfersbetweenmasterperipheralsandslaveperipherals.Throughaswitchfabricthe
CPUcansenddatatotheEMIFAwithoutaffectingadatatransferbetweenthePCIandtheDDR2
memorycontroller.Theswitchfabricsalsoallowforseamlessarbitrationbetweenthesystemmasters
whenaccessingsystemslaves.
TwotypesofbusesexistintheC6454device:databusesandconfigurationbuses.SomeC6454
peripheralshavebothadatabusandaconfigurationbusinterface,whileothersonlyhaveonetypeof
interface.Furthermore,thebusinterfacewidthandspeedvariesfromperipheraltoperipheral.
Configurationbusesaremainlyusedtoaccesstheregisterspaceofaperipheralandthedatabusesare
usedmainlyfordatatransfers.However,insomecases,theconfigurationbusisalsousedtotransfer
data.Forexample,dataistransferredtotheMcBSPviaitsconfigurationbus.Similarly,thedatabuscan
alsobeusedtoaccesstheregisterspaceofaperipheral.Forexample,theEMIFAandDDR2memory
controllerregistersareaccessedthroughtheirdatabusinterface.
TheC64x+Megamodule,theEDMA3trafficcontrollers,andthevarioussystemperipheralscanbe
classifiedintotwocategories:mastersandslaves.Mastersarecapableofinitiatingreadandwrite
transfersinthesystemanddonotrelyontheEDMA3fortheirdatatransfers.Slavesontheotherhand
relyontheEDMA3toperformtransferstoandfromthem.MastersincludetheEDMA3trafficcontrollers
andPCI.SlavesincludetheMcBSPandI2C.
TheC6454devicecontainstwoswitchfabricsthroughwhichmastersandslavescommunicate.Thedata
switchfabric,knownasthedataswitchedcentralresource(SCR),isahigh-throughputinterconnect
mainlyusedtomovedataacrossthesystem(formoreinformation,seeSection4.2).ThedataSCR
connectsmasterstoslavesvia128-bitdatabusesrunningataSYSCLK2frequency(SYSCLK2is
generatedfromPLL1controller).Peripheralsthathavea128-bitdatabusinterfacerunningatthisspeed
canconnectdirectlytothedataSCR;otherperipheralsrequireabridge.
Theconfigurationswitchfabric,alsoknownastheconfigurationswitchcentralresource(SCR)ismainly
usedbytheC64x+Megamoduletoaccessperipheralregisters(formoreinformation,seeSection4.3).
TheconfigurationSCRconnectsC64x+Megamoduletoslavesvia32-bitconfigurationbusesrunningata
SYSCLK2frequency(SYSCLK2isgeneratedfromPLL1controller).AswiththedataSCR,some
peripheralsrequiretheuseofabridgetointerfacetotheconfigurationSCR.NotethatthedataSCRalso
connectstotheconfigurationSCR.
Bridgesperformavarietyoffunctions:
•Conversionbetweenconfigurationbusanddatabus.
•WidthconversionbetweenperipheralbuswidthandSCRbuswidth.
•FrequencyconversionbetweenperipheralbusfrequencyandSCRbusfrequency.
Forexample,theEMIFAandDDR2memorycontrollerrequireabridgetoconverttheir64-bitdatabus
interfaceintoa128-bitinterfacesothattheycanconnecttothedataSCR.
NotethatsomeperipheralscanbeaccessedthroughthedataSCRandalsothroughtheconfiguration
SCR.
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