JESD204B character 传输协议讲解(简单透彻)

1、nderstandingcontrolcharactersinJESD204BHeresacloserexaminationofthecontrolcharactersthatareemployedintheJESD204interface.ByJonathanHarrisProductpplicationsEngineernalogDevicesInc.TheshifttoJESD204Basthedigitalinterfaceofchoiceforhighspeeddataconvertersiswellunderway.TheJESD204interfacewasreleasedini

2、tsoriginalform,JESD204,in200revisedtoJESD204Ain200,andinAugust20011revisedoncemoretothecurrentJESD204B.TheinterfaceringsefficiencyandoffersseveraladvantagesoverprecedingtechnologieslikeLDS.DesignsemployingJESD204Benoytheenefitsofafasterinterfacetokeeppacewiththefastersamplingratesofconverters.Therei

3、sareductioninpackagepincountwhichleadstosmallerpackagesandlesstraceroutes.Thestandardappliestoothanalogue-to-digitalconvertersADaswellasdigital-to-analogueconvertersDA,andisprimarilyintendedasacommoninterfacetofieldprogrammalegatearraysFPGAsforexampletheXilinxKintexorertexplatformsutitmayalsoeusedwi

4、thASICs.JESD204Bdiffersfromitspredecessorsinup-frontcomplexityduetothenewtermsandparametersthatitintroduces.Inthisarticle,welltakeacloserexaminationofthecontrolcharactersthatareusedintheJESD204interface.nderstandingthecontrolcharactershelpsprovideaetterunderstandingofhowalinkissynchronisedandaligned

5、.ThishelpsdesignerstounderstandhowtodeuglinkissuesthatmayarisewhenprototypingadesignwiththeJESD204interface.Eachofthecontrolcharactersperformsadifferentfunctionandhelpsmaintainthealignmentofdataonthelinkaswellassynchronisationanderrormonitoring.Ifanexpectedcharacterismissedoranunexpectedcharacterisr

6、eceived,thereceiverknowsthatanerrorexists.HowitworksisthattheJESD204Bwordsgetmappedintovalid10encodedwordsandaresetupinframesandmulti-frameswithspecificrules.Intheprocess,the10encodingprovidessomeenefitsfortheserialdatalinkyusingcontrolcharactersthatprovidetheailitytoperformvariouslanealignmentfunct

7、ions.Therearefivemaincontrolcharactersutilisedinthe10encodingthatallowforvariousfunctionsintheJESD204Bdatastream.ThesecharactersareK,F,A,R,andQcontrolcharacters.What a bunch of characters!TheK=K2.controlcharacterisusedinthecodegroupsynchronisationprocessviathesynchronisationinterfaceyassertingSC.nce

8、thereceiverissuesasynchronisationrequest,thetransmittereginsemittingK=K2.characters.ThereceiversynchronisesandwillwaitforatleastfourconsecutiveK=K2.characters.Thereceiverthendeactivatesitssynchronisationrequest.Thisprocessisdoneaccordingtothesuclassofoperation.Forsuclass0nodeterministiclatency,there

9、ceiverdeactivatesthesynchronisationrequestonanyframeoundaryafterfourconsecutiveK=K2.charactershaveeenreceived.Forsuclass1and2deterministiclatencywithSSREForSC,respectively,thereceiverdeactivatesthesynchronisationrequestonanylocalmulti-frameclockoundaryafterfourconsecutiveK=K2.charactershaveeenreceiv

10、ed.Figure1:/K/controlcharacterstreaming. TheA=K2.3controlcharacterisusedformulti-framealignmentintheserialdatastream.Itisinsertedattheendofamulti-frameythetransmitterundercertainconditions.Inthiscase,whenthelastoctetofthecurrentframeattheendofamulti-frameisequaltothelastoctetofthepreviousframe,anA=K

11、2.3characterreplacesthatoctet.Thishappensevenifthelastoctetofthepreviousframewasalsoacontrolcharacter.TheR=K2.0controlcharacterisusedtoindicatetheeginningofamulti-frame.Ifthetransmitteremitsaninitiallanealignmentsequence,thentheR=K2.0isthefirstnon-K2.characterthatistransmitted.Duringaninitiallaneali

12、gnmentsequence,thetransmitterwillalwaysemitanR=K2.0charactertoindicatetheeginningofamulti-frameandanA=K2.3charactertoindicatetheendofamulti-frame.TheQ=K2.4controlcharacterisusedduringtheinitiallanealignmentsequencetoindicatetothereceiverthattheconfigurationdataisgoingtostart.Itisimportanttorememerth

13、atthisparticularcontrolcharacterisonlyusedduringtheinitiallanealignmentsequenceandnotduringanyotherphaseofdatatransmission.2:/R/,/,and/Q/contolchaacts.TheF=K2.7controlcharacterisusedforframealignmentintheserialdatastream.Thischaracterisinsertedattheendofaframeythetransmitterundercertainconditions.Wh

14、enthelastoctetofthecurrentframewhichisnotthelastoctectofamulti-frameisequaltothelastoctetofthepreviousframe,aF=K2.7characterisusedtoreplacethatoctet.owever,ifacaseariseswherethelastoctetinthepreviousframewasaF=K2.7character,thecurrentoctetisnotreplaced.:/and/contolchaactfamandmlt-famalnmnt.Allofthes

15、econtrolcharacters,K,F,A,RandQ,aregivenalongwiththeir10itinaryrepresentationsinthe.Therearetwocorresponding10itinaryrepresentationsofeachcontrolcharactersothatDCalanceisprovidedinthedatatransmissionandtheinterfaceisAC-coupled.ThisfollowssuitwiththedatawhichalsohasDCalanceinthe10datawords.Thisschemea

16、lignswiththe10encodingdescriedinIEEE02.3.ItisimportanttoecomefamiliarwiththemanyaspectsoftheJESD204interfaceasitecomestheinterfaceofchoiceforADandDAconverters.Ithasmorecomplexitythanitsprecedinginterfacetechnologies.owever,JESD204Bdoesprovidemanyenefits.ThecontrolcharactersusedinJESD204allowthelinkt

17、oesynchronisedproperlyaswellasmonitoredforalignment.ThevariouscontrolcharacterseachperformsaspecificfunctioninmaintainingthelinketweentheJESD204transmitterandreceiver.ThesecontrolcharactersalsoprovideamethodofmonitoringtheJESD204Blinkforerrors. Table: 8b/10b control characters.Asyoupeeltheonionackmo

18、reandmoreontheJESD204Bstandard,themanyenefitssuchuilt-inalignment,monitoring,anderrordetectionecomeevidentdemonstratingtheroustnessofthestandard.JESD204Bisreadytocarrythelatestgenerationsofdataconvertersforwardintofastersampleratesandsmallerpackages.1.TheJESD204BSurvivalGuide2.JEDECStandardJESD204BJuly2011.JEDECSolidStateTechnologyAJonathanHarrisisaproductapplicationsengineerinthehighspeedconvertergroupatAnalogDevicesinGreensoro,C.Hehasoveryearsofexperi