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4InterruptConditions
4.1CPUInterrupts
4.2GeneralDescription
acklD rsv prio tt 1010 destID sourcelD Reserved srcTID
Reserved DoorbellReg# rsv
Doorbellbit
CRC
PHYLOGTRALOGTRAPHY
5 3 2 2 4 8 8 8 8
9 2
1
4
16
1632
16
4
2
10
info(msb)
8
info(lsb)
8
InterruptConditions
ThissectiondefinestheCPUinterruptcapabilitiesandrequirementsoftheperipheral.
ThefollowinginterruptsaresupportedbytheRIOperipheral.
•Errorstatus:Eventindicatingthatarun-timeerrorwasreached.TheCPUshouldreset/resynchronize
theperipheral.
•Criticalerror:Eventindicatingthatacriticalerrorstatewasreached.TheCPUshouldresetthesystem.
•CPUservicing:EventindicatingthattheCPUshouldservicetheperipheral.
TheRIOperipheraliscapableofgeneratingvarioustypesofCPUinterrupts.Theinterruptsservetwo
generalpurposes:errorindicationandservicingrequests.
SinceRapidIOisapacketorientedinterface,theperipheralmustrecognizeandrespondtoinbound
signalsfromtheserialinterface.TherearenoGPIOorexternalpinsusedtoindicateaninterruptrequest.
Thus,theinterruptrequestsaresignaledeitherbyanexternalRapidIOdevicethroughthepacket
protocolsdiscussedasfollows,oraregeneratedinternallybytheRIOperipheral.
CPUservicinginterruptslagbehindthecorrespondingdata,whichwasgenerallytransferredfroman
externalprocessingelementintolocalL2memory.ThistransfercanuseamessagingordirectI/O
protocol.Whenthesingleormulti-packetdatatransferiscomplete,theexternalPE,ortheperipheral
itself,mustnotifythelocalprocessorthatthedataisavailableforprocessing.Toavoiderroneousdata
beingprocessedbythelocalCPU,thedatatransfermustcompletethroughtheDMAbeforetheCPU
interruptisserviced.Thisconditioncouldoccursincethedataandinterruptqueuesareindependentof
eachother,andDMAtransferscanstall.Toavoidthiscondition,alldatatransfersfromtheperipheral
throughtheDMAusewrite-with-responseDMAbuscommands,allowingtheperipheraltoalwaysbe
awarethatoutstandingtransfershavecompleted.InterruptsaregeneratedonlyafterallDMAbus
responsesarereceived.SinceallRapidIOpacketsarehandledsequentially,andsubmittedonthesame
DMApriorityqueue,theperipheralmustkeeptrackofthenumberofDMArequestssubmittedandthe
numberofresponsesreceived.Thus,asimplecounterwithintheperipheralensuresthatdatapackets
havearrivedinmemorybeforesubmittinganinterrupt.
ThesendingdeviceinitiatestheinterruptbyusingtheRapidIOdefinedDOORBELLmessage.The
DOORBELLpacketformatisshowninFigure45.TheDOORBELLfunctionalityisuser-defined.This
packettypeiscommonlyusedtoinitiateCPUinterrupts.ADOORBELLpacketisnotassociatedwitha
particulardatapacketthatwaspreviouslytransferred,sotheINFOfieldofthepacketmustbeconfigured
toreflecttheDOORBELLbittobeservicedforthecorrectTIDinfotobeprocessed.
Figure45.RapidIODOORBELLPacketforInterruptUse
SPRUE13A–September2006SerialRapidIO(SRIO)85
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