以太网PHY物理层学习资料PCS子层

1、Clause24100BASE-XPhysicalCodingSubk(PCS)UNIVERSITYofNEWHAMPSHIREINTEROPERABILITYLABORUniversityofNewHampshireInteroperabilityLaboratory100i100iPresentationOverview:LocationintheOSIStackInterfacewithReconciliationsublayerInterfacewithPhysicalMediumAttach(PMA)sublayerPCSSublayerFunctionalityPCSintheOS

2、IModelLANCSMA/CDLAYERSAPPLICATIONPRESENTATIONSESSIONTRANSPORTNETWORKDATALINKPHYSICALHIGHERLAYERSLLC-LOGICALUNKCONTROLRECONCILIATIONMACCONTROL(OPTIONAL)CLAUSE31MACMEDIAACCESSCONTROLCLAUSE4PCSPMAPMDAUTONEGPHYCLAU5CLAU5CLAUSCLAUJOSIREFERENCEMODELLAYERSMEDIUM100BASE-TXijvjvUniversityofNewHampshire_Inter

3、operabilityLaboratoryInterfacewithReconciliatSublayerThePCSsendsandreceivesnibblesofdataiReconciliationsublayer.Ituses16signalstoreceivedata,andtoindicatecolllsionsandgRXsignals一RXD4linesforreceiveddatanibbles一RX_ER一indicateareceiveerror一RX_DVindicatethereceptionofvaliddata一RX_CLKusedastimingreferen

4、eefortransferofUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iInterfacewithReconciliatSublayerTXsignals一TXD4linesfortransmittingdatanibbles一TX_EN一indicatethebeginningofframetransmis一TX_ER一usedtoforceatransmissionerrorbymeinvalidcodegroup一T

5、X_CLK一usedastimingrefereneefortransferofCarrierIndicationsignals一CRS一indicatescarrieractivityonthereceivechai一COL一indicatesacollisiononthemediumIinterfacewithPMASublaSerialBitStream-ThePCSandPMAtransfercodebitsthroughserialbitstreams.ControlStatusPMATXLINKMONITORAt111FAR-ENDFAULT-!GENERATE:一Thelink_

6、statusindicationisgeneratedbythePMAandsenttothePCS.Thisindicatestheintegrityofthelink(READY,OK,orFAIL).PCSSublayerFunctionsThe100BASE-XPCSprovidesthefolioservices:一4B/5BEncodingandDecoding一CarriersenseandCollisiondetection一StreamserializationtotheunderlyingPM/一MappingoftheMilsignalstothePMA4B/5BEnco

7、dingThePCSlayerreceives4-bitdatanibblesfroThisresultsinatotalof24differentdatasynThePCSneedsadditionalcontrolsymbolstostartandendofthedatastream,anderrorsendstation.ThePCSwouldlikesufficienttransitiondenssignal(variedtransitionofIsandOs)toaidrecoveryatthefar-endPMD.Thisisaccomplishedthrough4B/5Benco

8、din(4-bitdatanibbletoa5bitcodegroup.4B/5BInthe5bitworldwenowhave25symbolsrUcode-groups,z:一The16datasymbols(0-9,A-F)stillexistbutwithrepresentations.A4-bitData0,0000,getstranslccode-group/0/,11110.一/J/and/K/definethestartofastream一/T/and/R/definetheendofastream一/I/definestheidlecode-groupthatseparate

9、sstre一/H/indicatesanintentionalerrorusedintransmis一Theremaining10code-groupsareinvalidandsheintentionallytransmitted(exceptforrepeaters)aJkkUniversityofNewHampshire一InteroperabilityLaboratoryaJkkUniversityofNewHampshire一InteroperabilityLaboratory4B/5BDataSymbolListPCScode-group4:043210NameMIHTXD/RXD

10、)3210Interpretatio1111000000DalaO0100110001Data11010020010Data21010130011Data30101040100Data40101150101Data50111060110Data60111170111Data71001081000Data81001191001Data910110A1010DataA10111B1011DataB11010C1100DalaC11011D1101DataD11100E1110DataE11101F1111DataFTable24-14B/5Bcode-groupsDATA100iUniversit

11、yofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100i4B/5BControlSymbolLiscoNTROLPCScode-group4:043210NameMil(TXD/RXD)3210Intorg11111IundcGnedIDLE;usedasinter-streamfi11000J0101Slart-of-StreamDcliiralwaysusedinpairsv10001K0101Start-of-StreamDeliaalwaysus

12、edinpairsm01101TundctincdEnd-of-StreamDclimalwaysusedinpairsv00111RundefinedEnckof-StreamDclimalwaysusedinpairsvUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100i4B/5BInvalidSymbolLisNVALIDPCScode-uroup4:043210NameMil(TXD/RXD)3210Interp00100H

13、UndefinedTransmitError;usedtoforcesignaling00000VUndefinedInvalidcode00001VUndefinedInvalidcode00010VUndefinedInvalidcode00011VUndefinedInvalidcode00101VUndefinedInvalidcode00110VUndefinedInvalidcode01000VUndefinedInvalidcode01100VUndefinedInvalidcode10000VUndefinedInvalidcode11001VUndefinedInvalidc

14、odeUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iFrom4Bto5BAfewchangestakeplacewhenconvertingfi一WhenTX_ENisassertedontheMil(toindicatettaMACframe)thefirsttwonibblesofdataarerep/J/and/K/code-groupsThefirsttwonibblesofcthefirsttwonibblesoft

15、heMACpreamble(0101Ccombinationofcode-groupsisknownastheStartDelimiter(SSD).一WhenTX_ENisde-asserted(toindicatetheendcframe)thePCStransmitsthe/T/and/R/code-gr(combinationofsignalsisknowastheEndofStrew(ESD).一AftertransmittingtheESDthePCStransmitstheiFrom5Bto4BAfewmorechangestakeplacewhenconveito4B:一Whe

16、nthePCSreceivestheSSD(/J/K/)itrep01010101.Thisisinterpretedaspreambleb一WhenthePCSreceivestheESD(/T/R/)itde-tolethigherlayersknowtheyarenoIongerrdata一WhenthePCSreceivesoneoftheinvalidcodorthe10others)itsignalsanerrorviatheR；PCSEncapsulationMACFrameoctets866246-15004PhysicalLayerstreamFigure24-5PCSenc

17、apsulation4B/5BSummaryOnlythePCSknowsabout5-bitcode-(exceptforthePMA)/J/and/K/replacepartoftheMACfrpreamble/T/and/R/replacepartoftheinter-fr/H/istheonlyinvalidcodegroupthatintentionallybetransmitted(exceptforepeaters)CarrierandCollisionDeteThePCScandetectactivityonboththetran：receivechannels.Ifitdet

18、ectsonlyonechaniactivityitsignalsCRSontheMil(meaningtlactivityonthemedium).IfbothchannelsshowactivitythePCScanscollisiontohigherlayersviatheMIFsCOLsiThisisonlycollisiondetectiornotenforcemlayerenforcescollisionsinHalfDuplexmodeThebehavioroftheCOLsignalisundefInedPhyisinFullDuplex.StreamSerialization

19、TXD3210血RXD3210皿4321014B/5BEncoderr5PCSEncodingMil(25millionnibbles/s)5B/4BDecoderMil(25millionnibblesPCSDecodinc(25millioncode-grou9876543210PMAInterface(125millionnrzi-bits/s)PMAInterface(125millionnrzib/s)UniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabili

20、tyLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iFigure24-6PCSreferencediagramUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iPCSStateDiagramsThefollowingstatediagra

21、msdefinettandreceivefunctionsofthePCSThestatediagramsarethefinalwordPCSshouldperformWellbeginbyshowingavalidinstanotransmissionandreception,thenshoverrorcasesoccur.ijvjvUniversityofNewHampshire一InteroperabilityLaboratory100iijvjvUniversityofNewHampshire一InteroperabilityLaboratory100iBEGINlink_saJkkU

22、niversityofNewHampshire一InteroperabilityLaboratoryStreamTransmissionDatacode-groupsaretransmittedtotheunderlyingPMAonlywhenTX_ENisTRUEOtherwisetheIdlecode-group(/I/)istansmittedTheSSDistransmittedduringthefirsttworeceivednibblesafterTX_ENisTRUE(effectivelyignoringthefirsttwonibblesofdata)Figure24-8T

23、ransmitsiTheESDistransmittedafterTX_ENisFALSE.IDLEPCSinitializationstate.transmitting=FALSEPCSisnottransmittingCOL=FALSEThereisnocollisionindicatedbecausethePCSisnottransmitting.tx_bits4:0=IDLETransmitthe5-bitIDLEcode-group(11111)ExitcasessentCodeGroup.indicateandTX_EN=FALSELoopthroughtheIDLEstatege

24、ttingdatanibblesaslongasthereisnotransmissionsentCodeGroup.indicateandTX_EN=TRUEandTX_ER=FALSEExittheIDLEstatewhenatransmissionisstartedwithouterrorindicationBEGINlinkstatisentCodeGroupimsentCodeGroup.indicateandTX_EN=TRUEandTX_ER=TRUEFollowtheerrorpathofthestatediagramwhenbothTXENandTXERareTRUEUniv

25、ersityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iBEGINlink_saJkkUniversityofNewHampshire一InteroperabilityLaboratoryBEGINlinksUBEGINlinkstatBEGINlinkstiBEGINlinkstiUniversityofNewHampshireInteroperabilityLaboratoryUniversityofNewHampshireInterope

26、rabilityLaboratoryBEGINlink_saJkkUniversityofNewHampshire一InteroperabilityLaboratoryExitcasesTXEN=FALSEERRORCHECKFromthisstatethePCSloopsthroughthetransmissionofvaliddataandthetransmissionoferrors(/H/).Whenthetransmissionendsitexitstotheendofstreampath.TXEN=TRUEandTXER=FALSEGototheTRANSMITDATAstatei

27、ftransmissionisenabledandtransmiterrorisFALSETXEN=TRUEandTXER=TRUEIfanerrorisforcedviaTX_ERthenthePCSenterstheTRANSMITERRORstate.A.sontCodoSTARTSTREAMKsemCodoGroup.indicatesontCodoGroupindicatotransmflling,FALSECOL5FALSEtx.Wts|4O|iDLEIDLEsontCodoGroupindicatoTXER=FALSEsontCodoGroupindicatoTXENxFALSE

28、COLjreceivingtx_bfts4:0iSSD2*ERRORCHECKsentCodeGroupiTX.ENrTRUETX_ER=FALS!STARTSTREAMJtransmitting*TRUECOLjrocoivingtx.Ms40sSSD1TX_ENXTRUETXER=FALSETXEN=FALSExittheERRORCHECKloopwhenthetransmissionisnoIongerenabled.UniversityofNewHampshireInteroperabilityLaboratoryUniversityofNewHampshireInteroperab

29、ilityLaboratoryBEGINlink_saJkkUniversityofNewHampshire一InteroperabilityLaboratorysontCodoGroupindicatoBEGINlinkBEGINlinkBEGINlink_saJkkUniversityofNewHampshire一InteroperabilityLaboratoryBEGINlinkBEGINlinkBEGINlink_saJkkUniversityofNewHampshire一InteroperabilityLaboratoryENDSTREAMRSecondpartof/T/R/tra

30、nsmission.IDLEtx_bits4:0=ESD2TransmitESD2,/R/(00111).ThedatanibblefromsentCodeGroup.indicateisignored.transmittingFALSECOLjFALSEtx.bits4:01jIDLEExitcasessentCodeGroup.indicateExittotheIDLEstatewhenacodegroupisavailable.ThisendsastreamtransmissionfromthePCS.UniversityofNewHampshireInteroperabilityLab

31、oratorysentCodeGroup.indicateTX_EN二FAsontCodGGroup.indicateENDSTREAMTsentCodeGrsentCodGGroup.indicatGsentCodeGroup.indicateTXEN=FALSECOLjreceivingtx_brts4:0jEN8DE(TXD)transmittingFALSECOLjFALSElx.bits4:0jESDITX.EN=TRUETX_ER=FALSETRANSMITDATASTARTSTREAMJtransmittingCOLjIx-bits4:0TRUEreceivingjSSD1sen

32、tCodeGroup.indicaleTXER=FALSEsentCcsentCodeGroiTX_EN二TRI頁TX_ER=FAISTARTSTREAMKERRORCHECKCOLreceivingtx.blts4:0SSD2TXTXENDSTREAMRtx_bits4:0ESD2BEGINlink_sBEGINlink_sUniversityofNewHampshire一InteroperabilityLaboratoryUniversityofNewHampshire一InteroperabilityLaboratoryBEGINlink_saJkkUniversityofNewHamp

33、shire一InteroperabilityLaboratorysentCodeGroup.indicateTransmitErrorsThetransmiterrorsignal(TX_ER)canoccurduring/J/,/K/,ordata(shownbytheredarrows)TransmissionerrorsshouldonlyoccurwhenbothTX_ENandTX_ERareTRUE.IfTX_ERisTRUEduringthetransmissionoftheSSD(/J/K/),avalidSSDistransmittedanyway.Atleastoneerr

34、orcode-groupistransmittedafterwardsFigure24-8TransmitsiTransmissionerrorsarecreatedbysendingthe/H/code-groupBEGINlink_saJkkUniversityofNewHampshire一InteroperabilityLaboratoryBEGINlink：BEGINlink_saJkkUniversityofNewHampshire一InteroperabilityLaboratoryBEGINlink_saJkkUniversityofNewHampshire一Interopera

35、bilityLaboratoryUniversityofNewHampshireInteroperabilityLaboratoryBEGINlinkstatBEGINlinkstatUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLabora

36、toryUniversityofNewHampshireInteroperabilityLaboratoryUniversityofNewHampshireInteroperabilityLaboratory100iStreamReceptionCarrierisdetectedbyseeingtwononcontiguousZEROSwithinany10bitsofthedatastream.Avalidstreambeginswith/J/K/.Avalidstreamcontainsonlydatacode-groups.Figure24-11ReceivestAvalidstream

37、endswith/T/R/BEGINVBEGINVUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100ilinkstaRX_DVIDLEreceivingRX_ERRX.DVjFALSEjFALSEjFALSElinkstatusrx.brts0=rx_bits9:2vIDLEPCSreceptioninitialization

38、state.ThePCSalsoentersthisstateafteralinkfailureoccurswhilethePCSisnotreceivingvaliddata(linkstatus*OKandRXDV=FALSE).receiving=FALSEPCSisnotreceivingdataRX_ER=FALSENoreceiveerrorsRX_DV=FALSENoreceptionofvaliddata.ThevalueontheMildatasignalsareundefinedatthispointbutareignoredbytheReconciliationSubla

39、yeruntilRXDVisasserted.Exitcaseslink_status=OKandrx_bits0=0andrx_bits9:2llllllllExittheIDLEstatewhenthelinkisokay,a0isinthefirstrx_bitsvectorandanother0ispresentintheotherbitvectors.Thetwonon-contiguous0zsmeanscarrierisdetected.Also,exitingtheIDLEstatedependsonavalidlinkstatus.BEGINUniversityofNewHa

40、mpshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100ilink_staRXDVBEGINIDLEreceivingRX_ERRXDVFALSEFALSEjFALSElink_status:rx_bits0=rx.brts9:2vCARRIERDETECTTRUEreceivingrxbrts9:0rxbits9:0CARRIERDETECTThePCSdetec

41、tscarrier(somethingotherthanidle).ThePCSentersthisstateonceitseestwononcontiguousZEROSwithintenbits.receiving=TRUEPCSisnowreceiving(something)Exitcasesrx_bits9:0*/I/J/Ifthebitsintherx_bitsvectordonotmatchthe/I/and/J/code-groupsthenmoveontotheBAD_SSDstate.ThePCSmustdetectacompleteSSDthatindicatesaval

42、idstream.rx_bits9:0=/I/J/Ifthebitsintherx_bitsvectormatchthe/I/and/J/code-groupsthenmoveontotheCONFIRMKstate.ThePCSmustdetectacompleteSSDthatindicatesavalidstream.CONFIRMKConfirmtheexisteneeofavalidSSD.Exitcasesrx_bits9:5=/J/andrx_bits4:0$/K/Ifthebitsinthefirsthalfoftherx_bitsvectormatch/J/andthesec

43、ondhalfdoesnotmatch/K/thenaninvalidSSDhasbeendetected.ThePCSmovesontotheBADSSDstate.link_staRXDV(rx.brts9:5=/J/)(rx.brts4:0/K/)IDLEreceivingRX_ERRX.DVjFALSEjFALSEjFALSElink_status=rx_bits0=rx.brts9:2、Twbrts9:0CARRIERDETECTreceivingJTRUErx.bits(9:0*CONFIRMK(rx.brts9:Jv(rx.bits4rx_bits9:5=/J/andrx_bit

44、s4:0=/K/Ifthebitsinthefirsthalfoftherx_bitsvectormatch/J/andthesecondhalfmatches/K/thenavalidSSDhasbeendetectedThePCSmovesontotheSTARTOFSTREAMJstate.BEGINUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabili

45、tyLaboratory100ilinksBEGINBEGINijBjvUniversityofNewHampshire一InteroperabilityLaboratoryijBjvUniversityofNewHampshire一InteroperabilityLaboratoryUniversityofNewHampshireInteroperabilityLaboratory100iSTARTOFSTREAMKThePCShasdetectedavalidSSDandwillnowcommunicatethistotheRSRXD=0101Adata5issentinplaceofth

46、e/K/codegroup.ExitcasesUCTThePCSunconditionallytransitions(UCT)tothenextstate,RECEIVE.TRUEreceivingrx_bits9:0UCTrxbits9:0w/l/J/RXD0101link_staRXDVIDLEreceivingRX_ERRXDVjFALSEjFALSEjFALSElinkstatus:rx_bits0=rxjjrts9:2CARRIERDETECTvVCONFIRMKSTARTOFSTREAMJRX_DVjRXDTRUEj0101gotCodeGroi(rx_bits9:1v(rxbit

47、s4:1ISTARTOFSTREAMKBEGINvBEGINvUniversityofNewHampshireInteroperabilityLaboratory100iIDLEroceivingRX-ERRXDVjFAIjFAIjFAIlink_rx_ti,rx_bireceivingCARRIERDEHT1CONFIRMKSTARTOFSTREARX_DVjTRUERXDjOhgotCoSTARTOFSTREARXDJ019UCTRECEIVErx.bits9:0=ESDbrts9:5=/J0*bits4:0/K/)rx_bits9:01/J/gotCodeGroupmdicatorx.b

48、its9:0=IDLESRECEIVEAfterreceivingavalidSSDthePCSisreadyforthestreamofdataandESD.ThePCSalsodetectserrorsinthestream.ExitcasesgotCodeGroup.indicateandrx_bits9:0=ESDThePCSreceivesavalidESD.gotCodeGroup.indicateandrx_bits9:5DATAandrx_bits9:0ESDandrx_bits9:0*IDLESThePCSreceivessomethingotherthanESD,IDLE,

49、ordata.EnterDATAERRORstate.gotCodeGroup.indicateandrx_bits9:0=IDLESThePCSreceivesidlebeforeanESD.EnterthePREMATUREENDstate.gotCodeGroup.indicateandrx_bits9:5DATAThePCSreceivesacode-groupthatisamemberoftheDATAsetofcode-groups.UniversityofNewHampshireInteroperabilityLaboratoryBEGINUniversityofNewHamps

50、hireInteroperabilityLaboratoryUniversityofNewHampshireInteroperabilityLaboratory100iExitcasesUCTreceivingCONFIRMKrx_bits9:0=ESDlink_rx_birxbibrts9:5=/J0*brts4:0/K/)rx_b(ts9:0*/VJ/CARRIERDEHT1IDLErecoivingjFAIRX.ERjFAIRXDVJFAItCodeGroupmdicaierx.bits9:0=IDLESSTARTOFSTREARX.DVjTRUERXDongotCoSTARTOFSTR

51、EARXDJ01UCTRECEIVEDATAThePCSreceivesacode-groupthatisamemberoftheDATAsetofvalidcode-groups.ThePCSdecodesitintoits4-bitrepresentation.RXER=FALSEUponreceptionofavaliddatacode-groupthePCSsetsthereceiveerrorindicationtoFALSE.RXD=DECODE(rx_bits9:5J)ThePCSdecodesthe5-bitcode-groupintothe4-bitdatarepresent

52、ationandsendsittotheRS.ThePCSunconditionallytransitions(UCT)backtotheRECEIVEstatetoreceivemoredata.BEGINUniversityofNewHampshireInteroperabilityLaboratoryUniversityofNewHampshireInteroperabilityLaboratory100iENDOFSTREAMThePCShasdetectedavalidESDandhasenteredthisstate.rx_bits9:0=lllll11111ThePCSwaits

53、inthisstateuntilitseestwo/I/code-groups.ThismeansthePCSignoresanycode-groupsthatcomeaftertheESDthatarenotidle.ExitcasesUCTThePCSunconditionallytransitions(UCT)backtothebeginningIDLEstateafterseeingidle.ItsetsRXDVtoFALSEsothattheRSknowsthestreamhasendedanditcannowignoretheMildatasignals.UniversityofN

54、ewHampshireInteroperabilityLaboratoryBEGINrx.brts9X)=IDLESENDOFSTREAMrxjxts(9:0)j1111111111receiving*-FALRX.ER-FALRXDVFALIDLEiinksrx_bit,r_bitCONFIRMK(rx.brts9:5=/J/)(rx_brts4:0*/K/)(rx_t.(nc_tCARRIERDETEreceivingJTFSTARTOFSTREA1rx.bits9:00/VJ/RX.DVTRUERXDj01CgotCocSTARTOFSTREAFRXD01CgotCodeGroup.in

55、dicatenc.bits9:0=ESDgotCodeGroup.kxlicaierx.bits9:0=IDLESgotCodeGroup.indicatoFigure24-11ReceivestUCTRECEIVEBEGINUniversityofNewHampshireInteroperabilityLaboratoryUniversityofNewHampshireInteroperabilityLaboratory100iReceptionErrorsReceiveerrorscanhappenduringthe/J/K/,duringthedata,orduringthe/T/R/R

56、X_ERisassertedtosignalanerror.TheReconciliationSublayershouldmakesurethatwhenbothRX_ERandRX_DVareassertedtheMACwilldetectanerrorintheframerx.brts【9:0=IDLESrx.bits9:0UCTFALFALFALreceivingRX_ERRXDVCARRIERDETEreceivingJTF(rx.brts(9:5)=/J/)(rx.brts4:0*/K/)ENDOFSTREAMm_brts(9:0)j1111111111gotCodeGroup.in

57、dicatolink,rx_bit,r_bitrx.biCONFIRMK(rx-ti(rx-fcSTARTOFSTREA1RX.DVTRUERXDj01CgotCocSTARTOFSTREAFRXD01CUCTgotCodeGroup.indicatonc.bits9:0=ESDgotCodeGroup.indicaierx.bits9:0=IDLESPREMATUREENDRXERJTRUEFigure24-11ReceivestBEGINBEGINUniversityofNewHampshireInteroperabilityLaboratory100iUniversityofNewHampshireInteroperabilityLaboratory100iUniversit