內(nèi)容講義教程decode 8b10b

8b/10bDecoderDS258(v1.0)March28, Drop-inmoduleforVirtex?,Virtex-E,Virtex-,Virtex-Pro?,Spartan?-,Spartan-E,andSpartan-3Decodingof10-bitsymbolsinto8-bitbytesandanpanying“K”bitDecodingof268uniquetransmittedcharacters:256bytevaluesand12special(“K”)charactersDecodertracks“runningdisparity”toverifythatdisparitysequenceofthereceivedsymbolsisvalidChoiceofanLUT-basedimplementation,whichusesthatusesoneofthededicatedon-chipblockmemory

OptionalRUN_DISPoutputtrackstherunningdisparityofthedecoderOptionalDISP_ERRoutputindicatesaviolationoftherunningdisparityrulesOptionalSINITinput sthedecoderintoauser-definedknownstateOptionalCEinputcanbeusedtoselectivelyenableorstallthedecoderOptionalDISP_INsupportschainingmultipledecodersOptionalCODE_ERRoutputindicatesthattheinputsymboldidnotcorrespondtoavalidmemberofthecodesetOptionalSYM_DISPoutputprovidesdisparityinformationonthecurrentsymbolbeingdecodedOptionalND(newdata)outputindicatesDOUThasanewdecodedsymbolonitsoutputBlockRAMimplementationcanimplementsecondary(“B”)decoderwithalmostnoadditionalresourceTobeusedwithv5.2iandlateroftheXilinxCOREGeneratorSystem

Figure1:DecoderSchematicDIN[9DOUT[7DISPSYMDISP[1RUNCODEDISPDINB[90]DISPINDOUTB[7SYMDISPB[1SINITRUNDISPCECODEERRDISPERRCLKNDFigure2:DualDecoderSchematic?2003Xilinx,. .AllXilinxs, s,patents,andfurtherdiersareaslistedatxilinxcom/legalhtm.Allothersand sarethepropertyoftheirrespectiveowners.Allspecificationsaresubjecttochangewithoutnotice.NOTICEOFDI application,orstandard,Xilinxmakesnorepresentationthatthisimplementationisfromanyclaimsofinfringement.Youareresponsibleforobtaininganyrightsyoumayrequireforyourimplementaion.Xilinxexpresslydisanywarrantywhatsoeverwithrespecttotheadequacyoftheimplementation,ludingbutnotlimitedtoanywarraniesorrepresentationsthatthisimplementationisfromclaimsofinfringementandanyimpliedwarrantiesofmerchantabilityorfitnessforaparticularpurpose.8b/10b8b/10bDecoderThe8B/10BDecodercoreimplementsthefullcodesetpro-posedbyA.X.WidmerandP.A.Franaszek1.Thecodespecifiestheencodingofan8-bitbyte(256uniquedatawords)andanadditional12special(or“K”)charactersintoa10-bitsymbol,hencethe8b/10bdesignation.Anumberofcharacteristicsofthecodeschememakeitideallysuitedforhigh-speedlocalareaworks,computerlinks,oranyserialdatalink.ThecodeschemeisDC-balanced,whichisofparticularbenefitforactivegain,thresholdsetting,andequalizationofopticalreceivers.Thecodehasalimitedrunlength,nomorethanfiveconsecutiveonesorzeros,andaguaranteedtransitiondensity,whichpermitsclockrecoveryfromthedatastream.Thespecial(K)charactersareusefulaspacketdelimiters.Asubsetofthem,referredtoascom-mas,areuniqueinthattheirbitpatternneveroccursinastringofdatasymbolsandhencecanbeusedtodeterminesymbolboundariesatthereceivingend.Additionalrulesembeddedinthecodedesignallowmanyerrorstobedetectedatthereceivingend.Thecombinationofthesefeaturesallowsthereceivingendofanencoded8b/10bdatastreamtoextractthebit-rateclock,todeterminesym-bol(andpacket)boundaries,andtodetectmosttransmis-sionerrors.Thisisalldonewithacomparativelylowoverheadof25percent(each10-bitsymbolcontains8bitsofinformation)versus,forexample,aManchestercodewithits100percentoverhead.Becauseofitsmanyfeatures,thecodehasbeenusedinthephysicallayer(PHY)ofanumberofcurrentandemergingstandards,ludingFibreChan-nel,GigabitEthe,andRapidI/O,tonameafew.Thisdatasheetusesanumberoftermspresentintheorigi-nalIBMJournalpaper.Understandingthisterminologyiscriticaltoasuccessfulapplicationofthiscore.Mostimpor-ttheconceptof“Disparity.”Thedisparityofanyblockofdataisdefinedasthediffer-encweenthenumberofonesandzerosintheblock.Positiveandnegativerefertoanexcessof1sover0s,or0sover1srespectively.Eachencodedsymbolcanbeconsid-eredtobeablock.Thecodeschemeguaranteesthatanencodedsymbol'sdisparityisalwayseither0(fiveones,fivezeros),+2(sixones,fourzeros)or-2(fourones,sixzeros).Somebytevalueswillhavemorethanonepotentialsymbolencodingwiththeencodedsymbolpatterndeter-minedbythe“RunningDisparity.”Runningdisparityissim-plyarecordofthedisparityfortheaggregateofallthepreviouslyencodedsymbols.Forpacket-baseworkingapplications,therunningdisparityistypicallytrackedfromthestartofapacket.TheDecodertrackstherunningdisparityoftheinputdatastreamforerrorcheckingpurposes.At ofeach

10-bitencodedsymbol,therunningdisparitywillbe+1-1,whichequatestoa1or0respectivelyontheRUN_DISPoutput.Eachsymbol'sdisparityiscombinedwiththecurrentrunningdisparitytoproducethenewrunningdisparity.Sym-bolswithadisparityof0wouldthennotmodifytherunningdisparity[+1+(0)=+1]or[-1+(0)=-1].Symbolswithadis-parityof+2or-2wouldswaptherunningdisparitybetween+1and-1;e.g.,[+1+(-2)=-1]or[-1+(+2)=Ifthesymboldisparityisanythingotherthan+2,0,or-2,thedisparityofthe ingdataisinvalidandadisparityerrorisflagged(DISP_ERR=1).Suchanerroralsooccursiftherunningdisparityis+1andthesymboldisparityis+2,orwhentherunningdisparityis-1andthesymboldisparityis-2.MostinvalidinputsymbolswillalsoresultinadisparityRunningdisparityvalidityisalsoendatthesub-blocklevel.Sethe10-bitblockisactuallycomposedofa6-bitblockanda4-bitblock,thesamerulesforrunningdisparityapplyatthosesub-blockboundaries.Thedisparityofeachsub-blockmustbe+2,0,or-2.Therunningdisparityattheendofthesub-blockmustfollowtherulethatrunningdis-paritymustbe-1or+1.FailuretomeetthiscriteriawillalsobeflaggedasadisparityerrorbytheDecoder.TheDecoderusestheschemeinWidmerandFranaszek’spapertodecodethe10-bitinputsymbolintoan8-bitoutputvalue.Thepaper’snomenclaturedefinesthebitsofthe10-bitsymbolasabcdei_fghj,where‘a(chǎn)’istheLSBand‘j’istheMSB.This10-bitencodedsymbolispartitionedasa6-bitsub-block(abcdei)anda4-bitsub-block(fghj).Inthesameway,the8-bitoutputvalueisdefinedastheconcate-nationofa5-bitanda3-bitsub-block(ABCDEandFGHrespectively).Asdefinedintheoriginalpaper,these8bitsarenamedABCDE_FGHwhereAistheLSB,andHistheWhendecodingthe10-bitinputsymbol,thedecoderfirstdecodesthesixleastsignificantbitsabcdeioftheinputsymbolintothefiveleastsignificantbitsoftheoutput,ABCDE.Table1showsanexampleofthisdecodingforthesymboldesignatedD31.1.ThefiveoutputbitsABCDEequateto31indecimal(EDCBA=11111),thusprovidingthefirstpartofthesymbolname.Similarly,thefourmostsignif-icantbitsfghjoftheinputsymboldecodeintothethreemostsignificantbitsoftheoutputFGH.Thethreeoutputbits,FGH,representadecimal1,providingthesecondpartofthesymbolname(HGF=001).Table2definesthedecodingofthe12specialcommandsymbolsforbothpositiveandnegativedisparitycases.Thesespecialcharactersaredistinguishedfromthe256standardcharactersbytheKOUToutputbeingassertedwhenthesymbolisdecoded.TheDOUTvalueidentifieswhichofthetwelvespecialcharactershavebeendecoded.8b/10b8b/10bDecoderTable1:ExampleDecodingofd31.1forBothRunningDisparity(RD)987654321076543210jhgfiedcbaHGFEDCBA1001001010-00111111-100111010100111111Table2:DIN,KOUT,andDOUTforValidSpecialCharacter(7asMSB)jhgfiedcbaKHGFEDCBA0010111100100011100110100001110001110001100000111001111001001111100100111100101011110010101110001010000111010111001100111100101111100001100001110111110001001111001100111001011000011110011100010111110011011110010100000111101111000110111100111011100100100001111101110000011111001111111001110000011111111100000101011111111011111101010001111101110001011011111111011111010010011111101100010111011111111011110100010111111101000101111011111111011101000011111111108b/10b8b/10bDecoderTheoriginalpaperbyWidmerandFranaszekdefinesthe10-bitencodedsymbolasaserialstreamofbitsnamedabcdei_fghj.Thisencodedsymbolistransmittedseriallyfromatoj.The10-bitsymbolcontainssub-blocksof6-bitsand4-bits.Expressedinthismanner,the“a”bitisactuallytheLSBofthevalue,andthe“j”bitistheMSB.Inthedecoder,the10-bitDINbusreceivestheencodedsymbolasDIN<9:0>,whereDIN<9>istheMSB(the“j”bit)andDIN<0>istheLSB(the“a”bit).ThesameruleappliestotheDOUTdecodedoutputbyte.RepresentedasABCDE_FGHintheoriginalpaper,withAastheLSBandHastheMSB,theDOUT<7:0>busofthedecoderstoresthisvaluewithDOUT<7>,theMSB(the“H”bit)andDOUT<0>theLSB(the“A”bit).TheMSB/LSBorderinghasnoimplicationsfordatawords,buthasimplicationswhendecodingspecialcharacters(SeeTable2).TransmissionisalwaysLSB-first,sothatwhendeserializingencodedsymbols,DIN[0](a)isreceivedoveratransmis-sionlinefirst,andDIN[9](j)isreceivedlast.Thedecoderiscapableofdecodingonly10-bitsymbolsintotheappropriatecharacters.Itcontainsnotransmissionpro-tocolsemanticsandisnotcapableofdirectlymanipulatingserialdata.Whenreceivingserialtransmitteddata,logicexternaltothedecoderisneededtoconvertthe a-to-jbitstreamintotheDIN<9:0>symbolthatthedecoderinputbusrequires.Thiternallogicmustalsoberespon-sibleforpartitioningthe ingbitstreamatthepropersymbolboundariessothatthedecoderaccurayreceivesthecompleteencodedsymbol(jhgf_iedcba).Oncethedataisdecoded,thedecoderprovidesonlythedecodedbyte,Kvalue,anderrorflags.Allerrorcorrectionanddatainterpre-tation(suchasinterpretingasequenceofbytesasadatapacket,andrecognizingtheKcodesaspropercom-mands/delimiters)mustallbeperformedexternaltotheIfmorethanonedecoderisusedtodecodemultiplesym-bolsatatimeintolargerwords,therunningdisparityinputsandoutputsshouldbechainedtogether.TheRUN_DISPoutputofthefirstdecoderdrivestheDISP_INinputoftheseconddecoder.Thefinaldecoder'sRUN_DISPoutputisthenconnectedbacktotheDISP_INofthefirstdecoder.Notethatthiamplealsorequiresthattheinputclockstothetwodecoderstagesbesequenced;e.g.,notthesameclockoratleastthesameactiveclockedge.SignalnamesareshowninFigure1andFigure2anddescribedinTable3.

Clock-CLKTheDecoderisfullysynchronoustoitsappropriateclockport(CLK;CLK_Bforthe“B”decoder).AlldecoderinputportshavetheirsetuptimereferencedtotherisingedgeoftheCLK(orCLK_B)input.Alldecoderoutputsarealsosyn-chronoustotheirrespectiveCLKinput.Clockinputsareris-ingedgeactivebydefault;tomakethedecoder(s)respondtothefallingedgeofasystemclock,insertaninverterbetweenthesystemclockandthedecoder'sCLKinput.CLK_Bistheclockinputfortheoptionalsecondary“B”ClockEnable-CECE,anoptionalinput,canbeusedtostallthedecoder,pre-ventingitfromrespondingtochangesontheinputs.IfthedecoderhasaCEportandtheCEinputisinactive(logic0),transitionsontheclockportwillhavenoeffect.IfCEisactive(logic1)orisnotpresent,theinputswillbereadandoutputsupdatedoneveryrisingedgeoftheCLK.TheCE_BpinistheClockEnableforthe“B”Data-InputBus-DIN<9:0>DINistheinputbusthatprovidesthe10-bitencodedsym-boltothedecoder.Inthecaseofserialdatatransmission,itisimportanttonotethatDIN(0)istheleast-significantbitofthe10-bitencodedsymbol.DINmustbealignedonsymbolboundaries(D<0>=a,D<9>=j)forthedecodertoproducecorrectresults.DIN_Bisthedatainputbusforthe“B”SynchronousInitialization-SINITSINIT,anoptionalinput,initializesthedecodertoadefinedstate.IfSINITisactive(logic1)andCEisactive,theout-putsandinternalstateofthedecoderwillbesetontheris-ingedgeoftheclock.Inthiscase,DOUTwillbesettoauser-definedvalue,KERRwillbesettozero,andtheinter-nalrunningdisparitywillbesettoauser-definedvalue.ItismendedtoassertSINITattimeswhenthedecoder'sstatemustbeknown,suchasbeforereceivingapacket,toinsurethattherunningdisparityisinitializedcorrectlybeforeSINIT_Bisthesynchronousinitializationinputforthe“B”Data-OutputBus-DOUTDOUTisthedecodedoutputbyte.Subsequenttoeveryris-ingclockedge(providedthatCEisnotpresentandinac-tive),DOUTwillholdthedecodeddatabyte.Thedecodeddatabyteisthedecodedvalueofthe10-bitsymbolontheDINbusattheclockedge.DOUT_BisthedecodedbyteoutputfortheB8b/10b8b/10bDecoderTwoTwo10-bitEncodedTwo8-bitDecoded Figure3:SchematicIllustratingConnectionofMultipleCommandSymbolOutputFlag-KOUTKOUTindicatesthatthedecoded10-bitsymbolwastheencodingofacommandsymbolorspecialcharacter.LikeDOUT,KOUTisupdatedaftertherisingclockedgetoreflectthedecodedvalueoftheinputsymbolontheDINbus.WhenKOUTisinactive(logic0),the10-bitsymbolbeingdecodedisarepresentationofanordinary8-bitbyte(presentedonDOUT).WhenKOUTisactive(logic1),the10-bitsymbolisanencodingofoneofthe12specialchar-actersandthevalueontheDOUTbusindicatestheidentityofthespecialcharacter.KOUT_Bisthecommandsymboloutputflagforthe“B”

DisparityInput-DISP_INDISP_IN,anoptionalinput,overridesthedecoder'sinternaldisparity.Normally,therunningdisparity(seenontheRUN_DISPoutput)isfedback,andontherisingedgeoftheclockaddedtothesymboldisparityofthecurrentsym-boltoproducethenewrunningdisparity.WhenDISP_INispresent,however,thenewrunningdisparityaftertherisingclockedgeisdefinedasthesymboldisparitycombinedwithDISP_IN(insteadoftheoldrunningdisparity).Alogic0assertedontheDISP_INinputindicatesthataninputdis-parityof-1shouldbecombinedwiththecurrentsymboldis-parity,andalogic1assertedontheDISP_INinputindicatesaninputdisparityof+1shouldbeused.DISP_IN_Bisthedisparityinputforthe“B”8b/10b8b/10bDecoderTable3:DecoderInputandOutputI/OPinClock:Clockinput,alldecoderinputsaresampledandalloutputsareupdatedsynchronouslyontherisingedgeoftheCLKinput.CLK_Bistheclockinputfortheoptionalsecondary“B”ClockEnable:TheoptionalCEinputportcontrolswhetherornotthedecoder(High)orthedecoderwillnotchangestateinresponsetotheCLKinput.Whennotpresent,thedecoderwillalwayschangestateontherisingclockedge.CE_Bistheclockenableinputfortheoptionalsecondary“B”SynchronousInitialization:WhentheSINITinputportispresentandsetActive(High),thedecoderisinitializedontherisingedgeoftheclocktoadefinedstate.DOUTissettoauser-selectablesymbol.KERRissetto0.RUN_DISPissettoauser-defineddisparity.SINIT_Bisthesynchronousinitializationportforthe“B”DataInput:Encoded10-bitsymbolinputDIN_Bisthedatainputbusforthe“B”DisparityInput:Ifpresent,thisportisa inputfortherunningdisparitytowhichthecurrentsymbol'sdisparityisadded.Ifnotpresent,therunningdisparityusedisthedecoder'sinternalrunningdisparity.DISP_IN_Bisthedisparityinputportforthe“B”DataOutput:Thedecoded8-bitbyteresultingfromdecodingtheinput10-bitencodedsymbol.DOUT_Bisthedataoutputbusforthe“B”K(Command)Output:Iftheinputted10-bitencodedsymbolwasanencodingofoneofthe12commandcodes,KOUTwillbeActive(High).KOUT_Bisthecommandoutputflagforthe“B”CodeError:Ifpresent,CODE_ERRisActive(High)whenevertheinputted10-bitencodedsymboldoesnotcorrespondtoavalidmemberofthecodeset.CODE_ERR_Bisthecodeerroroutputflagforthe“B”decoder.CODE_ERRflagserrorsonlywhenthe10-bitcodeontheDISP_INbusisinherentlyinvalid.Tocatchallerrorsinaninputsequence,thisvaluemustbecombinedwithDISP_ERR.SymbolDisparity:Ifpresent,SYM_DISPdesignatesthedisparityofthemostrecentlydecodedsymbol:--ERROR/ZERO(Dependingon00-01-SYM_DISP_Bisthesymboldisparityoutputforthe“B”8b/10b8b/10bDecoderTable3:DecoderInputandOutputI/OPinRunningDisparity:Ifpresent,RUN_DISPdesignatestherunningdisparity,ludingthedisparityofthedatasymbolthathasbeendecoded.1=runningdisparityof0=runningdisparityof-RUN_DISP_Bistherunningdisparityoutputforthe“B”DisparityError:Ifpresent,DISP_ERRisActive(High)wheneverthemostrecentlydecodedsymbolviolatedrunningdisparityrules.Causesforadisparity ludeinvalidsymbolsandrunningdisparityviolationsatboththesymbolblockandsub-blocklevels.somecodesmaynotproduceaDISP_ERR,thoughthecodeis,bydefinition,invalid.Forthisreason,DISP_ERRshouldalwaysbecombinedwithCODE_ERRtodetectallerrors.NewData:IfpresentandCEispresent,NDisActive(High)whenevertheCEpinwasHighonthepriorclockcycle,indicatingthatnewdataresidesontheoutputND_Bisthenewdataoutputflagforthe“B”CodeErrorFlag-CODE_ERRCODE_ERR,anoptionaloutput,indicatesthatthe10-bitsymbolonthedata-inbusduringtherisingedgeoftheclockwasnotavalidmemberofthecodeset.Active(logic1)rep-resentsaCODE_ERR,andinactive(logic0)indicatesthatthe10-bitcodewasavalidmemberofthecodeset(althoughothererrorsmaystillexist).CODE_ERR_BisthecodeerrorflagfortheBSymbolDisparity-SYM_DISP<1:0>[SYM_DISP_B<1:0>]SYM_DISP,anoptionaloutput,representsthedisparityofthe10-bitsymbolcurrentlybeingdecoded.Ithasfourpos-siblevalues:10=Symbolhasdisparityof0(equalnumberof0'sand1'sinthesymbol(5zeros,5ones))00=Symbolhasdisparityof-2(twomore0'sinthesymbolthan1's(6zeros,4ones))01=Symbolhasdisparityof+2(twomore1'sinthesymbolthan0's(4zeros,6ones))11=Disparityerror(the10-bitsymbolhasaninvalidratioof0'sto1'sorthe6-bitor4-bitsub-blocksoftheof0(seecase10)Thesymboldisparityiscombinedwiththecurrentrunningdisparity(+1or-1)togeneratethenewrunningdisparityforthedecoder.

Mostapplicationswillnotrequiresymboldisparity,whichismostlyusefulasadebuggingaid.Todetecttransmissionfaults,theseimplementationswillmonitorDISP_ERR.SYM_DISP_BisthesymboldisparityfortheBRunningDisparity-RUN_DISPRUN_DISP,anoptionaloutput,exposesthecurrentrunningdisparityinthedecodertoexternallogic.Runningdisparity,bydefinition,mustbe+1or-1.TheRUN_DISPoutputusesalogic1torepresentarunningdisparityof+1,andalogic0torepresentarunningdisparityof-1.Therunningdisparity,oneachrisingedgeoftheclock,iscombinedwiththesymboldisparityofthesymbolbeingdecodedtoproducethenewrunningdisparityaftertheclockedge.WhentheDISP_INportispresent,therunningdisparitywillbebasedonthecurrent10-bitsymbolandtheDISP_INpin.WhentheDISP_INportisnotpresent,therunningdisparityisbasedonthecurrent10-bitsymbolandthedecoder'sinternalrunningdisparity.TheinitialstateoftheRUN_DISPoutputisuserconfig-urableviathecore’sGUI.RUN_DISP_BistherunningdisparityoftheBDisparityErrorFlag-DISP_ERRDISP_ERR,anoptionaloutput,indicatesthepresenceofanerrorintherunningdisparityofthedecoder.Adisparity8b/10b8b/10bDecodererror(representedbyalogic1)canbecausedbymanyIfthesymboldisparityofthe10-bitsymbolcurrentlybeingdecodeddoesnotabidebytherulesforrunningdisparity,itwillproduceadisparityerror.Itmaybeavalid10-bitencodedsymbol,butitmustbeusedinthecorrectcontextofrunningdisparity.Inparticular,ifthecurrentrunningdisparityis+1,thesymboldisparitymustbe0or-2.Or,ifthecurrentrunningdisparityis-1,thesymboldisparitymustbe0or+2.Ingeneral,therunningdisparitymustalwaysremain-1or+1.Thesamerulesforrunningdisparityapplytothe6-bitand4-bitsymbolsub-blocks.Violatingrunningdisparityrulesatthislevelwillgenerateadisparityerror.Adisparityerrorwillalsooccurforamajorityofinputsthatarenotamemberofthevalidcodeset.TheseadditionalcasescsobedetectedbecausetheTable4:XCOFileParametersandtheDefault

CODE_ERRoutputwillbeDISP_ERR_BistheDisparityErroroutputflagforthe“B”NewDataOutput-NDND,anoptionaloutput,indicatesthatalldecoderoutputshavebeenupdatedonthemostrecentrisingclockedge.Thisindicatestodownstreamlogicthatalloutputs(DOUT,KOUT,allerrorflags,etc.)havebeenupdatedwiththeresultsofthenewlydecodedsymbolatthelastrisingedgeoftheclock.TheNDoutputisadelayedversionofCE,tak-ingonthevalueofCEattherisingedgeoftheclockoneachclockcycle.IftheCEinputportisnotpresent,NDisnotavailable.NDissettologic0ontheclockcyclefollow-inganSINITinputofalogic1.ND_Bisthenewdataoutputflagforthe“B”XCOFileDefaultGUIASCtextstartingwithalet ndbaseduponthefollowingcharacterset:a-z,0-9,and_Oneofthe:true,Oneofthe:true,Oneofthe:true,Oneofthe:true,Oneofthe:true,Oneofthe:true,Virtex:D0.0withnegativerunningVirtex-:D0.0orD10.2orD21.5eachwitheitherapositiveornegativerunningdisparity.(Note:DOUTwillbesettothesynchronousresetD0.0Oneofthe:true,Oneofthe:true,Oneofthe:true,Oneofthe:true,Oneofthe:true,Oneofthe:true,Oneofthe:true,Oneofthe:true,8b/10b8b/10bDecoderTable4:XCOFileParametersandtheDefaultXCOFileDefaultGUIOneofthe :true,Oneofthe :true,Oneofthe :true,TheXCOfileparameters,values,andGUIdefaultsareshowninTable4.NamesofXCOfileparametersandtheirparametervaluesareidenticaltothenamesandvaluesshownintheGUI,exceptthatunderscorecharacters(_)areusedinsteadofspaces.ThetextinanXCOfileiscaseCoreResourceUtilization&TheBlockRAM-baseddecoderrequiresthree(4K-bit)VirtexBlockRAMsplusasingleadditionalslice,aswellasnomorethanfourCLB'sfortherunningdisparityandnewdatalogic.IfaVirtex-deviceistargeted,onlyone(16K-bit)BlockRAMisrequired,plusthesameadditionalsliceandextralogic.Foreitherarchitecture,aseconddecodercanbegeneratedusingthesameBlockRAMresource,configuredinadual-portmode.Theonlyadditionallogicneededtoimple-menttheseconddecoderisasecondadditionalsliceandnomorethanfourmoreCLBsforthesecondsetofrunningdisparityandnewdatalogic.

Thecoreperformanceisgatedentirelybytheclocktooutandsetuptimesofthetargeteddevice.Theworst-caseper-formanceforallVirtexfamilieswillbe100MHz.1.A.X.WidmerandP.A.FranaszekADC-BALANCED,PARTITIONED-BLOCK,8B/10BTRANSMISSIONIBMJournalofResearchandDevelopment,Volume27,Number5,September1983.ThiscoremaybedownloadedfromtheXilinxIPCenterforusewiththeXilinxCOREGeneratorSystemv5.2iandlater.TheXilinxCOREGeneratorSystemtoolisbundledwithallAllianceSeriesSoftwarepackages,atnoadditionalcharge.ToorderXilinxsoftware,pleasevisittheXilinxSiliconXpressoCafeorcontactyourlocalXilinxsalesrepresenta-InformationonadditionalXilinxLogiCOREmodulesisavail-ableontheXilinxIPCenter. DS258(v1.0)2003年3月28日產(chǎn)品規(guī)格特性適用于Virtex.、Virtex-E、Virtex-、 Pro.、Spartan.-、Spartan-E和Spartan-3FPGA解碼的插入式模塊將10位符號轉(zhuǎn)換為8位字節(jié)和隨附的“K”位解碼268個唯一傳輸字符：256個字節(jié)值和12個特殊（“K”）于LUT的實現(xiàn)（使用FPGA片）或基于塊存儲器的實現(xiàn)（使用專用片上塊存儲器塊之一）可選RUN_DISPDISP_ERRSINITCEDISP_INCODE_ERRSYM_DISPND（新數(shù)據(jù)）輸出DOUTBlockRAM（“B”）XilinxCOREDIN[9:0]DOUT[7:0]v5.2iDISP_INKOUTSYM_DISP[1:0]SINITRUN_DISPCECODE_ERRDISP_ERRCLKND1：22003Xilinx,. 。所有Xilinx商標、注冊商標、專利和進一步免責聲明均在 、應用程序或標準的一種可能實現(xiàn)，Xilinx8B/10B解碼器核心實現(xiàn)了A.X.提出的完整代碼集。威德默和P.A.1.該代碼指定8（256）12（或“K”）10為8b/10b。該代碼方案的許多特性使其非常適合高速局域網(wǎng)、計算機鏈路或任何串行數(shù)據(jù)鏈路。限的運行長度，不超過五個連續(xù)的10，以及有保證的轉(zhuǎn)換密度，這允許從數(shù)據(jù)流恢復時鐘。特殊(K)（稱為逗號）是唯一的，因為它們的位模式開銷10位符號包含8位信息）完成的，而曼徹斯特碼則需要100%的開銷。由于其眾多功能，該代碼已用于許多當前和新興標準的物理層(PHY)，其中包括光纖通道、千兆位以太網(wǎng)和快速I/O等。差異此數(shù)據(jù)表使用了原始IBMJournal 心至關重要。最重要的是“差異”的概念。任何數(shù)據(jù)塊的差異被定義為塊中1和0的數(shù)量之間差異。正數(shù)和負數(shù)分別指1001。每個編碼符號可以被視為一個塊。該編碼方案0（五個一，五個零）、+2（六個一，四個零）2（四個一，六個+1或-1，分別相當于RUN_DISP輸出上的1或0。每個符號的差異與當前運行差異相結合以產(chǎn)0[+10)1]1(0)1]22+1112)1]1(+2)1]2、02，(DISP_ERR1064差異的相同規(guī)則適用于這些子塊邊界。每個子塊的視差必須是+2、02。子塊末尾的運行差異必須遵循運行差異必須為-1+1解碼器使用Widmer和Franaszek 中的方案將10位輸入符號解碼為8位輸出值。該 命名法將10位符號的位定義為abcdei_fghj，其中“a”是LSB，“j”是MSB。該10位編碼符號被劃分為6位子塊(abcdei)和4位子塊(fghj)。以同樣的方式，8位輸出值被定義為5位和3位子塊（分別為ABCDE和FGH）的串聯(lián)。正如原始 中所定義的，這8位被命名為ABCDE_FGH，其中A是LSB，H是MSB。106abcdeiABCDE51D31.1ABCDE31(EDCBA=11111)，從而提供了符號名稱的第一部分。類似地，輸入符號的四個最高有效部分(HGF=001)。212256KOUTDOUT9865432107654321jhgiedcbaHGFEDCBAD31.11001001010-10011111-11001110101+10011112：DIN、KOUTDOUTDIN[9:0]KOUTDOUT[7:0DOUT（7作為MSB）jhgiedcbaKHGFEDCBAK28.000101110100110110100001110001110001100000111001111001001111100100111100101011110010101110001010000111010111001100111100101111100001100001110111110001001111001100111001011000011110011100010111110011011110010100000111101111000111110110110010010000111110111000001111100111111100111000001111111110000010101111111101111110101000111110111000101101111111101111101001001111110110001011101111111101111010001011111110100010111101111111101110100001111111110Widmer

的原 將

位編碼符號定義為名為abcdei_fghj是值的LSB，“j”位是MSB。在解碼器中，10DINDIN9:0DIN<9>MSB（“j”位），DIN<0>是LSB（“a”位）少量）。相同的規(guī)則適用于DOUT解碼輸出字節(jié)。原 中表示為ABCDE_FGH，A為LSB，H為MSB，解碼器的DOUT<7:0>總線將該值與DOUT<7>、MSB（“H”位）和DOUT一起存儲<0>LSB（“A”）MSB/LSB（2）最后接收DIN[9](j)。ajDIN9:0>(jhgf_iedcba)。一旦數(shù)據(jù)被解碼，解碼器僅提供解碼的字節(jié)、K值和錯誤標志。所有糾錯和數(shù)據(jù)解釋（K個解碼器的RUN_DISP輸出驅(qū)動第二個解碼器的DISP_IN輸入。然后，最終解碼器的RUN_DISP輸出連接回第一個解碼器的DISP_IN。123時間均以CLK（或CLK_B）輸入的上升沿為參考。所有解碼器輸出也與其各自的CLK輸入同步。時鐘輸入默認為上升沿有效；要使解碼器響應系統(tǒng)時鐘的下降沿，請在系統(tǒng)時鐘和解碼器的CLK時鐘使能-CE[CE_B]CECECE（0），CE（1）或不存在，則將在CLK的每個上升沿讀取輸入并更新輸出。CE_B引腳是“B”解碼器的時鐘使能。DIN<9:0>[DIN_B<9:0>]DIN10DIN(0)10DIN（D<0>=a、D<9>=j）上對齊，以便解碼器產(chǎn)是同步初始化-SINIT[SINIT_B]]SINIT是一個可選輸入，將解碼器初始化為定義的狀態(tài)。如果SINIT有效（邏輯1）并且CE有效，則解碼器的輸出和 情況下，DOUT將被設置為用戶定義的值，KERR將被設置為零，并且 DOUT[DOUT_BDOUT（CE在且不活動），DOUTDIN10DOUT_BB3：KOUTKOUT10DOUTKOUTDINKOUT（0）10