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acklD rsv prio tt ftype
ftype=1011
destID
sourcelD msglen ssize msgseg/xmbox double-word0 double-word1 ...
double-wordn-2 double-wordn-1 CRC
PHY
LOG
TRA
LOG
TRAPHY
5 3 2 2 4 8 8 4 4 4 64 64
(n-4)*64
64 64 16
16n*64+16164210
n*64+64
letter
2
mbox
2
SRIOFunctionalDescription
Figure17.MessageRequestPacket
Thisenablestheletterandmailboxfieldstoinsteadallowfourconcurrentsingle-segmentmessagesto
sixty-fourpossiblemailboxes(256totallocations)forasourceanddestinationpair.Themailboxmapper
directstheinboundmessagestotheappropriatequeuebasedonapre-programmedroutingtable.It
basesthedecisionontheSOURCEID,MSGLEN(thesizeindicateswhetherthemessageissegmented),
MBOX,LETTER,andXMBOXfieldsoftheRapidIOpacket.
Thereare32programmablelook-uptableentriesformappingmailboxestoqueues.Eachentryconsists
oftworegisters,RXU_MAP_LnandRXU_MAP_Hn,whichareshowninFigure18.Adetailedsummaryof
theseregister'sfieldisinSection5.50.Intotal,thereare64registers,ataddressoffsets0800h–08FCh.
Eachentrystoresthequeuenumberassociatedwiththemessage’sintendedmailbox/letter.Ifa
mailbox/letterisnotsupportedordoesnothaveamappingtableentry,themessageisdiscardedandan
ERRORresponsesent.Themappingentriescanexplicitlycalloutamailboxandlettercombination,or
alternatively,themaskfieldscanbeusedtograntmultiplemailbox/lettercombinationsaccesstoaqueue
usingthesametableentry.Amaskingvalueof0inthemailboxorlettermaskfieldsindicatesthatthe
correspondingbitinthemailboxorletterfieldwillnotbeusedtomatchforthisqueuemappingentry.For
example,amailboxmaskofallzeroswouldallowamappingentrytobeusedforallincomingmailboxes.
Themappingtableentryalsoprovidesasecurityfeaturetoenableordisableaccessfromspecificexternal
devicestolocalmailboxes.ThesourceIDfieldindicateswhichexternaldevicehasaccesstothemapping
entryandcorrespondingqueue.AcompareisperformedbetweenthesourceIDoftheincomingmessage
packetandeachrelevantmailbox/lettertablemappingentrySOURCEIDfield.Iftheydonotmatch,an
ERRORresponseissentbacktothesender,andthetransactionisloggedinthelogicallayererror
managementcaptureregisters,whichsetsaninterrupt.APROMISCUOUSbitallowsthissecurityfeature
tobedisabled.WhenthePROMISCUOUSbitisset,fullaccesstothemappingentryfromanysourceIDis
allowed.NotethatwhenthePROMISCUOUSbitisset,themailbox/letterandcorrespondingmaskbits
arestillineffect.WhenthePROMISCUOUSbitiscleared,itequalsamaskvalueofFFFFh,andonlya
requestwiththematchingsourceIDisallowedaccesstothemailbox.
Eachtableentryalsoindicatesifitusedforsingleormulti-segmentmessagemapping.Singlesegment
messagemappingentriesutilizeallsixbitsofthemailboxandcorrespondingmaskfields.Multi-segment
entriesusesonlythe2LSBs.Thenumberofsimultaneoussupportedmulti-segmentmessagesis
determinedbythenumberofdedicatedRXqueuesasdiscussedfurtherbelow.Itisrecommendedto
dedicateamulti-segmentmappingentryforeachsupportedsimultaneousletter.Essentially,lettermasks
shouldbeavoidedformulti-segmentmappingtoreduceexcessiveretries.Notethatitispossibleto
configurethetableentriessuchthatincomingsinglesegmentandmulti-segmentmessagesaredirected
tothesamequeue.Toavoidthiscondition,properlyprogramthemappingtableentries.
SPRUE13A–September2006SerialRapidIO(SRIO)45
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