Filter
Top Products
www.ti.com
2.3.15.2DaisyChainOperationandPacketForwarding
2.3.15.3EnablingMulticastandPacketForwarding
SRIOFunctionalDescription
Table31.MulticastDeviceIDOperation
LocalDeviceIDMulticastDeviceID
DeviceRegisterOffsetRegisterOffsetEndpointDeviceRequirements
TMS320TCI64820080h0084hAcceptsdiscretemultipleDestIDsfrom
incomingpacket
Someapplicationsmayrequiredaisychainingofdevicestogetherversususingaswitchfabric.Typically,
theseapplicationsarelowcostimplementations.Daisychainshavevariablesystemlatencydependingon
devicepositionwithinthechain.Daisychainimplementationsalsohavereducedbandwidthcapabilities,
sincethelinkbandwidthdoesn’tchange,thebandwidthallocatedtoeachdeviceinthechainislimited
(sumofdevices’individualbandwidthneedscan’texceedlinkbandwidth).
Tosupportdaisychainorringtopologies,theperipheralfeaturesahardwarepacketforwardingfunction.
Thisfeatureeliminatestheneedforsoftwaretobeinvolvedinroutingapackettothenextdeviceinthe
chain.Thebasicideabehindthehardwarepacketforwardinglogicistoprovideaninputporttooutput
portpathsuchthatthepacketsneverleavetheperipheral(noDMAtransfer).Asimplecheckofan
in-comingpacket’sDestIDversusthedevice’sDeviceIDandMulticastIDisdonetodetermineifthepacket
shouldbeforwarded.Ifthepacket’sDestIDmatchesDeviceID,thepacketisacceptedandprocessedby
thedevice.Ifthepacket’sDestIDmatchestheMulticastID,thepacketisacceptedbythedeviceand
forwardedbasedontherulesoutlinedinSection2.3.15.1.Ifthepacket’sDestIDdoesn’tmatcheither,the
packetissimplydestroyedorforwarded,dependingonthewhetherthehardwarepacketforwardingis
enabled.
Additionally,itisbeneficialtobeabletoonlyforwardapacketifthedestinationIDisoneofthedevicesin
thechain/ring.Otherwise,aroguepacketmaybeforwardedendlesslyusingupvaluablebandwidth.The
hardwarepacketforwardingusesa4entrymappingtableshowninTable32andTable33.These
mappingentriesallowprogrammableselectionofoutputportbasedonthein-comingpacketsDestID
range.Sincethepacketforwardingisdoneatthelogicallayerandnotthephysicallayer,CRCswillbe
regeneratedforeachforwardedpacket.
Inordertoenablemulticastsupport,bit5oftheSP_IP_MODE(offset0x12004)mustbesetto1.The
multicastmodeisdisabledbysimplywritingthesamedeviceIDintotheregisterslistedinTable31.
HardwarepacketforwardingcanbedisabledbyassigningallthetableentryUpperandLowerdeviceID
boundariesequaltothelocalDeviceIDvalue.
Figure42.PacketForwardingRegisternfor16-BitDeviceIDs(PF_16B_CNTLn)Offsets0x0090,
0x0098,0x00A0,0x00A8
3116150
16BIT_DEVID_UP_BOUND16BIT_DEVID_LOW_BOUND
R/W-FFFFhR/W-FFFFh
LEGEND:R/W=Read/Write;-n=Valueafterreset
Table32.PacketForwardingRegisternfor16-BitDeviceIDs(PF_16B_CNTLn)FieldDescriptions
BitFieldValueDescription
31–1616BIT_DEVID_UP_BOUND0000h–FFFFhUpper16-bitDeviceIDboundary.DestIDabovethisrange
cannotusethetableentry.
15–016BIT_DEVID_LOW_BOUND0000h–FFFFhLower16-bitDeviceIDboundary.DestIDlowerthanthis
numbercannotusethetableentry.
SPRUE13A–September2006SerialRapidIO(SRIO)81
SubmitDocumentationFeedback