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Manoj Sharma Tanikella, Sr. R&D Engineer)Amitkumar Shrichand Gound, Sr. R&D Engineer)Synopsys
Overcoming Inter-Symbol Interference with MIPI PHYs using Training Sequences
©2017MIPIAlliance,Inc.
Agenda• Trainingsequencerequirements• ADAPTsequenceinMIPIM-PHY®• AlternatesequenceinMIPID-PHY℠• CalibrationsequencesinMIPIC-PHY℠• Summary
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©2017MIPIAlliance,Inc.
TrainingSequenceRequirements• Overviewonadaptiveequalizer• Purposeoftrainingsequences
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©2017MIPIAlliance,Inc.
AdaptiveEqualizerOverview
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Transmitter ReceiverEqualizer
01010011001110101010High-speedDATA
Filter AdaptiveEqualizer
DataProcessing
TrainingSequence
©2017MIPIAlliance,Inc.
PurposeofTrainingSequences
• Bitpatternsusedinadaptiveequalizermoduleareknownastrainingsequences• Receivermustrealizesequenceswellinadvance,sothatreceivercancompareandoptimize
itsco-efficientforproperDATAreception• SystemcansendDATAoncetrainingsequenceiscomplete• MostcommonlyusedtrainingsequencesarePseudoRandomBitSequences(PRBS)• Example:PRBS9,PRBS32,etc.
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©2017MIPIAlliance,Inc.
ADAPTSequenceinMIPIM-PHY• WhatisADAPT?• WhyandwhenADAPTsequenceisrequired?• PRBS9handling• ADAPToperation• Futurescope
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©2017MIPIAlliance,Inc.
WhatisADAPT?• Thetrainingsequenceusedtooptimizetheequalizersettingsof
thereceiver,inthiscaseM-RX,isknowasADAPT• ADAPTwasintroducedinMIPIM-PHYv4.0forhigherdatarate
HS_G4gear• ADAPTconsistsofMK0+PseudoRandomBitSequence+bit1’b0• PRBSwithequationX9 +X5 +1(PRBS9)isused
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Synopsys
©2017MIPIAlliance,Inc.
WhyandWhenADAPTSequenceisRequired?• AsMIPIM-PHYstartedsupportinghigherspeedHS_G4gear,inter
symbolinterferenceandnoiseincreased• In-ordertore-tuneequalizersettings,ADAPTsequencewas
introducedastrainingsequence• ADAPTsequenceorADAPTsub-stateisusedbeforestartingwith
HS-G4DATA• ADAPTSequence:PREPAREà ADAPTPATTERNà BURSTEND
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SynopsysPREPARE ADAPTPATTERN
(MK0+encodedPRBS9+1b0) BURSTEND
©2017MIPIAlliance,Inc.
PRBS9Handling• PRBS9isacombinationof9linear-shiftregisterswhereoutputof5th and9th
registersarexored andfeedbackisprovidedtoinput;Generates29 – 1=511bits• AsperstandardITU-TrecommendationO.150 and 0.153,patternbeginswithfirst
1’b1of9consecutiveONEs
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©2017MIPIAlliance,Inc.
PRBS9Handling(Continued…)
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• IfPRBS9isinitializedwithall1’s(1_1111_1111)onevery8clock,outputwillbe:• Bitformation1:11111111_10000011_11011111_00110010_00001001i.e.,‘hFFà ‘h83à
‘hDFà ‘h17à ‘h32à ‘h09• Bitformation2:11111111_11000001_11111011_01001100_10010000i.e.,‘hFFà ‘hC1à
‘hFBà ‘h4Cà ‘h90
©2017MIPIAlliance,Inc.
ADAPTOperation
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• ADAPToperationrequirements:– LinkshouldbeinHS_G4gear– M-RXattributeRX_ADAPT_Control shouldbeprogrammedto2’bX0
• WhereXcanbe0=InitialADAPTlengthor1=RefreshADAPTlength
• OnreceivingADAPTSTART.req fromprotocol,PHYmovestoADAPTsub-stateafterPREPAREandstartsdrivingADAPTsequenceforTADAPTlength;ADAPTsub-stateisendedbyBURSTENDSAP
WaveSnippetfromSynopsysM-PHYVIP
©2017MIPIAlliance,Inc.
ADAPTOperation
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• DurationforwhichcompleteADAPTsequencetakesisknownasTADAPT• M-RXhastwo8-bitcapabilityattributeforADAPTlength
– RX_HS_ADAPT_REFRESH_Capability– RX_HS_ADAPT_INITIAL_Capability
• M-TXTX_HS_ADAPT_Length shouldbegreaterorequaltoabovecapabilityvalues• AsperMIPIM-PHYspecificationTADAPT lengthiscalculatedasthefollowing:
Source:MIPIAllianceM-PHYv4.1
©2017MIPIAlliance,Inc.
FutureScope• ImproveperformancebyskippingSAVEstatebetweenADAPTand
DATAburst– i.e.,PREAPREà ADAPTà SYNCà DATA
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Synopsys
©2017MIPIAlliance,Inc.
AlternateSequenceinMIPID-PHY• Whatisalternatesequence?• Whyandwhenalternatesequenceisrequired?• PRBS9handling• Alternateoperation• Stateflow• Futurescope
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©2017MIPIAlliance,Inc.
WhatisAlternateSequence?• TrainingsequenceforoptimizationofreceiverequalizersettingsinMIPI
D-PHYusingPRBSpatternisknownasalternatesequence• AlternatesequencewasintroducedinMIPID-PHYv2.1• PRBSwithequationX9 +X5 +1(PRBS9)isused• Usedincombinationwithinitialskewcalibration
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Synopsys
©2017MIPIAlliance,Inc.
WhyandWhenAlternateSequenceisRequired?• SimilartoMIPIM-PHY,MIPID-PHYstartedsupportinghigherDATArate
2.5Gbpsorabove;Thisleadstosameintersymbolinferenceandnoise• Inordertore-tuneequalizersetting,alternatesequenceisintroducedas
trainingsequence• ItsmandatoryforDATAtransmissionabove2.5Gbps;designermaychooseto
supportalternatesequenceatorbelow2.5Gbps• Usedatlinkpowerupand/oronlinkre-initialization• AlternatesequencedividedintothreepartHS0à CalibrationSyncà
CalibrationPattern(PRBS9)
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Synopsys
HS0 CalibrationSync11110000 EOTLP00
CalibrationPatternPRBS9
LP11
©2017MIPIAlliance,Inc.
PRBS9Handling• MIPID-PHYwassecondPHYtointroducePRBS9forcalibration• PRBS9isinitializedwith9-bitvalue000000001• For8-bitdatawidthonevery8shifts,outputisformed;AsshowninfigureData[7:0]istheoutputfrom
shiftregister8to1
• For16/32bitdatawidth,samePRBS9willbeshifted16/32timestoformData[15:0]/Data[31:0]outputrespectively
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©2017MIPIAlliance,Inc.
AlternateOperation• Initialskewcalibrationisfollowedbyalternatecalibrationwhenlinkisabove2.5Gbps
speed• AfterInitialskewlinksstopstateLP11,followedbyHS-requestLP01à LP-00à HS0• AlternatecalibrationconsistsofcalibrationsyncandPRBS9pattern
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SynopsysSource:MIPIAllianceD-PHYv2.1
©2017MIPIAlliance,Inc.
StateFlow
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SynopsysSource:MIPIAllianceD-PHYv2.1
©2017MIPIAlliance,Inc.
FutureScope• Alternatesequencecanstartassoonasinitialskewpatternends,
insteadofgoingtoSTOPstate
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SynopsysReference:MIPIAllianceDPHYVersion2.1
©2017MIPIAlliance,Inc.
CalibrationSequencesinMIPIC-PHY• Whatiscalibrationsequence?• Typesofcalibrationsequence• Preamblehandlingandoperation• Alternatecalibrationhandlingandoperation• User-definecalibrationhandlingandoperation• Stateflow• Futurescope
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©2017MIPIAlliance,Inc.
WhatisCalibrationSequence?
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• SimilartoMIPIM-PHYandMIPID-PHY,inMIPIC-PHY,trainingsequenceusedtooptimizereceiverequalizersettingsisknownasCalibrationsequence
• CalibrationsequenceswereintroducedinMIPIC-PHYv1.2• TherearethreedifferentcalibrationsequencesthatwereintroducedinMIPIC-PHY• CalibrationsequencewillbetransmittedalongwithDATAburst• Calibrationsequencesareusedwhensystemoperatesabove3.0Gsps• Systemmaysupportcalibrationbelow3.0Gsps DATAtransmission
CalibrationSequence Sync PostLP-000 High-SpeedPacketDATA LP-111
©2017MIPIAlliance,Inc.
TypesofCalibrationSequence
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• MIPIC-PHYintroducedthreetypeofcalibrationsequence– Preamblecalibration– Alternatecalibration– User-definecalibration
• Preamblecalibration– seriesof1’ssymbol– It’sdifferentfromnormalpreamblepattern– all3’s– soreceivercaneasly identifydifferencebetween
normalandcalibrationpreamble• AlternateCalibration
– Startsrightafterpreamblecalibration– BeginswithalternateIDfollowedbyalternatepattern(PRBS9)similarasothertwoPHYs
• User-defineCalibration– Startsrightafterpreamblecalibration– Beginswithuser-defineIDfollowedbyuser-definepattern
©2017MIPIAlliance,Inc.
PreambleSequenceHandling&Operation
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• Thiscalibrationtypeonlyconsistsofpreamblesequencewhichissequenceof1ssymbol• Sequenceof1symboltransmissiondurationoft3-CALPREAMBLE• t3-CALPREAMBLE shouldbeminimumofonegroup(7UI)toamaximumof256groups(7X256=1792UI)• Oncepreamblesequencecompletes,followedbySYNCandDATA
• t3-CALPREAMBLEFortransmitterrangesfrom7UIto1792UI• Receivershouldspecifyminimumvaluebywhichitcandetectsequenceof1symbol• Maxforreceiveris1792UI
WaveSnippetfromSynopsysC-PHYVIP
©2017MIPIAlliance,Inc.
AlternateSequenceHandling
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Synopsys
– Alternatecalibrationisdividedintothreeparts• Preamblecalibration• AlternateID• Alternatesequence(PRBS9)
– PreambleCalibration• Alternatecalibrationfirststartswithpreamblecalibration• Preamblecalibration(symbolof1)istransmittedfort3-CALPREAMBLE duration
– AlternateID• In-ordertoidentifywhichtypeofcalibrationreceiverisreceiving,afterpreamblecalibrationseven“3”
symbolistransmittedtoindicatestartofalternatecalibrationfort3-ASIDdurationwhichisfixedat7UI– Alternatesequence
• SimilartoMIPIM-PHYandMIPID-PHY,MIPIC-PHYalsousesPRBS9sequence• SequenceisencodedinsymbolsusingtheMIPIC-PHY3-phasemapperandencoder• Transmittedfort3-CALALTSEQdurationwithminimumofonegroup(7UI)to2048groups(7X2048=14336UI)
©2017MIPIAlliance,Inc.
AlternateSequenceHandling(Continued…)
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Synopsys
• Data0toData15represent16-bitoutputdataData[15:0];dataoutputiscollectedonevery16clockshift
• Thereisnofixvalueforinitialseed;belowgraphicshowswhenPRBS9isinitializedwithseedvalue0x0001
©2017MIPIAlliance,Inc.
AlternateCalibrationOperation
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Synopsys
t3-CALALTSEQFortransmitteritrangesfrom7UIto14336UI;receivershouldspecifyrequiredminimum;maxforreceiveris14336UI
WaveSnippetfromSynopsysC-PHYVIP
©2017MIPIAlliance,Inc.
User-DefinedSequenceHandling
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• User-definedcalibrationisdividedintothreeparts:– Preamblecalibration– User-definedID– User-definedsequence
• Preamblecalibration– User-definedcalibrationalsofirststartswithpreamblecalibrationasdiscussedlast– Preamblecalibration(symbolof1)istransmittedfort3-CALPREAMBLE duration
• User-definedID– In-ordertoidentifywhichtypeofcalibrationreceiverreceiving,afterpreamblecalibration“3333313”
symbolistransmittedtoindicatestartofuser-definedcalibrationfort3-UDIDdurationwhichisfixedat7UI• User-definedsequence
– Asnamesuggestsitconsistsofuserdefinesequence– Drivenfort3-CALUDEFSEQdurationwhichcanbeminimumofonegroup(7UI)to2048group(14336UI)
©2017MIPIAlliance,Inc.
User-DefinedCalibrationOperation
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t3-CALUDEFSEQFortransmitterrangesfrom7UIto14336UI;receivershouldspecifyrequiredminimum;maxforreceiveris14336UI
WaveSnippetfromSynopsysC-PHYVIP
©2017MIPIAlliance,Inc.
StateFlow
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Synopsys
Cal.Preamble
AlternateID
3333333
User-DefinedID33333313
Sync HSData
AlternateSequencePRBS9
User-DefinedSequence
©2017MIPIAlliance,Inc.
FutureScope• Toreduceclockcycleinsteadofsendingcalibrationineachburst,we
cansendcalibrationinfirstburst(whendrivingabove3Gsps)
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SynopsysReference:MIPIAllianceDPHYVersion2.1
©2017MIPIAlliance,Inc.
Summary
MIPIM-PHY MIPID-PHY MIPIC-PHY
UsedatSPEED HS-G4gear Speedabove2.5Gbps Speedabove3.0Gsps
Lowerspeedsupport NO Maysupport Maysupport
Patternsused PRBS9 PRBS9 Preamble,PRBS9andUser-define
Calibrationflow BeforeactualData AlongwithInitialskewbeforeactualData
AlongwithDataburstitself
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• Asdiscussed,trainingsequencesareintroducedtore-tunethereceiverequalizercircuitsforproperdatareceptionathighspeed
• Thesepatternsareusedbeforeactualdatatransmissionsothatreceivercanselftuneitself
©2017MIPIAlliance,Inc.
VCVIP&TestSuiteforMIPI• MIPICSI-2
– CSI-21.1,1.2– D-PHY1.1,1.2– CSI-21.3compliantwithC-PHY1.0andDPHY1.2– CSI-22.0compliantwithC-PHY1.1andDPHY2.0
• MIPICSI-3v1.0• MIPIDSI
– DSI1.1,1.2compliantwithD-PHY1.1– DSI1.3compliantwithD-PHY1.2– DSI2.0compliantwithC-PHY1.0andDPHY2.0
• MIPIDigRF v41.10,1.00and0.64
Synopsys
• MIPIHSI
• MIPIDBI2.0Specification
• MIPIDPI2.0Specification
• MIPIUniPro
• MIPII3C
• MIPIRFFE
• MIPISoundWire
• MIPISPMI2.0
• MIPIM-PHYv4.1
©2017MIPIAlliance,Inc.
Synopsys®DesignWare®MIPIIPPortfolio
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