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msglen
msgseg/
xmbox
mbox letter
4 4 2 2
Single Segment
Mailbox 0 ... 63
Multi-Segment
Mailbox 0 ... 4
SOURCEID = SourceID allowed access if secure queue
Mailbox = Allowed mailbox for this mapping register
(Mask-able)
0b000000 - Mailbox 0
0b000001 - Mailbox 1
0b000010 - Mailbox 2
...
0b111111 - Mailbox 63
Letter = Allowed letter for this mapping register (Mask-able)
Segment Mapping = 0b0 - Single Segment (all six bits of Mailbox valid)
= 0b1 - Multi-segment (only 2 lsbs of Mailbox valid)
Promiscuous = 1, Full Access to the Queue for any SourceID
Queue ID = 0000 - 1111, corresponding Queue0 - Queue15
tt (Transport type) - 0b0 = matches the 8 lsb of the SOURCEID
0b1 = matches the full 16 bits of the SOURCEID
SRIOFunctionalDescription
Thisallowstheletterandmailboxfieldstoinsteadallowfourconcurrentsingle-segmentmessagesto
sixty-fourpossiblemailboxes(256totallocations)forasourceanddestinationpair.Themailboxmapper
directstheinboundmessagestotheappropriatequeuebasedonapre-programmedroutingtable.It
basesthedecisionontheSOURCEID,MSGLEN,MBOX,LETTER,andXMBOXfieldsoftheRapidIO
packet.
Figure16illustratesthelook-uptablesrequiredforprogrammablemappingofthemailboxtoqueue.There
are32programmablemappingentries.Eachmappingentryconsistsoftworegisters,RXU_MAP_Lnand
RXU_MAP_Hn.Eachentrystoresthequeuenumberassociatedwiththemessage’sintended
mailbox/letter.Ifamailbox/letterisnotsupportedordoesnothaveamappingtableentry,themessageis
discardedandanERRORresponsesent.Themappingentriescanexplicitlycalloutamailboxandletter
combination,oralternatively,themaskfieldscanbeusedtograntmultiplemailbox/lettercombinations
accesstoaqueueusingthesametableentry.Amaskingvalueof0inthemailboxorlettermaskfields
indicatesthatthecorrespondingbitinthemailboxorletterfieldwillnotbeusedtomatchforthisqueue
mappingentry.Forexample,amailboxmaskofallzeroswouldallowamappingentrytobeusedforall
incomingmailboxes.
Themappingtableentryalsoprovidesasecurityfeaturetoenableordisableaccessfromspecificexternal
devicestolocalmailboxes.TheSOURCEIDfieldindicateswhichexternaldevicehasaccesstothe
mappingentryandcorrespondingqueue.AcompareisperformedbetweenthesourceIDoftheincoming
messagepacketandeachrelevantmailbox/lettertablemappingentrySOURCEIDfield.Iftheydonot
match,anERRORresponseissentbacktothesender,andthetransactionisloggedintheLogicalLayer
ErrorManagementcaptureregisters,whichsetsaninterrupt,asdiscussedinSection4.3.APromiscuous
bitallowsthissecurityfeaturetobedisabled.WhenthePROMISCUOUSbitisset,fullaccesstothe
mappingentryfromanySOURCEIDisallowed.NotethatwhenthePROMISCUOUSbitisset,the
mailbox/letterandcorrespondingmaskbitsarestillineffect.WhenthePROMISCUOUSbitiscleared,it
equalsamaskvalueof0xFFFF,andonlythematchingSOURCEIDisallowedaccesstothemailbox.
Eachtableentryalsoindicatesifitusedforsingleormulti-segmentmessagemapping.Singlesegment
messagemappingentriesutilizeallsixbitsofthemailboxandcorrespondingmaskfields.Multi-segment
usesonlythe2LSBS.Thenumberofsimultaneoussupportedmulti-segmentmessagesisdeterminedby
thenumberofdedicatedRXqueuesasdiscussedfurtherbelow.Itisrecommendedtodedicatea
multi-segmentmappingentryforeachsupportedsimultaneousletter.Essentially,lettermasksshouldbe
avoidedformulti-segmentmappingtoreduceexcessiveretries.Notethatitispossibletoconfigurethe
tableentriessuchthatincomingsinglesegmentandmulti-segmentmessagesaredirectedtothesame
queue.Toavoidthiscondition,properlyprogramthemappingtableentries.
Figure16.QueueMappingTable(AddressOffset:0x0800-0x08FC)
42SerialRapidIO(SRIO)SPRU976–March2006
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