Filter
Top Products
www.ti.com
2.6Initialization
2.7Auto-Negotiation
PeripheralArchitecture
Note:Notservicingreadoperationsresultsindeadlock.Theonlywaytorecoverfromadeadlock
situationistoperformahardreset.Readoperationsaretypicallynotservicedduetoread
requeststhatareissuedtoanon-existentremoteVLYNQdeviceortheyarenotserviced
duetotryingtoperformreadsontheVLYNQmemorymappriortoestablishingthelink.
Generally,youshouldnotusereadoperationstotransferdatapacketssincetheserialnatureofthe
interfacecouldpotentiallyresultinlongerlatencies.SeeAppendixBformoreinformation.
SinceVLYNQdevicescanbecontrolledsolelyovertheserialinterface(thatis,nolocalCPUexists),an
automaticreliableinitializationsequence(withoutuserconfiguration)establishesaconnectionbetween
twoVLYNQdevices,justafteraVLYNQmoduleisenabledandauto-negotiationoccurs.Auto-negotiation
isdefinedinSection2.7.Thesamesequenceisusedtorecoverfromerrorconditions.However,itis
importanttoensurethattheappropriatebitsareconfiguredinthepinmuxregisterstoensurethatthe
VLYNQperipheralisactive.
Bit0intheVLYNQstatusregister(LINKbit)issetto1whenalinkisestablished.
Alinkpulsetimergeneratesaperiodiclinkcodeevery2048serialclockcycles.Thelinkislostwhentime
expiresandnolinkcodehasbeendetectedduringaperiodof4096serialclockcycles.
Auto-negotiationoccursafterreset.Itinvolvesplacinganegotiationprotocolintheoutbounddataand
processingtheinbounddatatoestablishconnectioninformation.Thewidthofthedatapinsontheserial
interfaceisautomaticallydeterminedatresetasapartoftheinitializationsequence.Foraconnection
betweentwoVLYNQdevicesofversion2.0andlater(VLYNQonDM643xdeviceisversion2.6),the
negotiationprotocolusingtheavailableserialpinsisusedtoconveythemaximumwidthcapabilityofeach
device.TheTXDdatapinsarenotrequiredtohavethesamewidthastheRXDdatapins.
TheautowidthnegotiationdoesnotoccuruntilaftercompletionoftheVLYNQ1.xlegacywidth
configuration,whichinvolvesaperiodof2000VLYNQ1.xsystemclockcyclesforconnectiontoVLYNQ
1.xdevices.AftertheVLYNQ1.xhasdetermineditswidth,itreceivestheVLYNQ2.xautowidth
negotiationprotocol.TheVLYNQ1.xdevicedoesnotrecognizethisprotocolandtransmitserrorcodes
overtheserialinterface.ThereceivederrorcodesallowtheVLYNQ2.xdevicestodeterminehowmany
serialpinsarevalidontheconnectedVLYNQ1.xdevice.
Oncethewidthisestablished,VLYNQfurtheridentifiestheversion(version1.xorversion2.x)ofthe
remoteVLYNQ.ThisbetterdeterminesthecapabilitiesoftheconnectedVLYNQdevice.Thisissoftware
readableviatheVLYNQauto-negotiationregister(AUTNGO),bit16(0=Ver1.x,1=Ver2.x),afterthe
linkhasbeenestablished.
SPRU938B–September2007VLYNQPort15
SubmitDocumentationFeedback