SAE-J1939-21-2006

®J1939-21REV.DEC2006SURFACEVEHICLERECOMMENDEDPRACTICEIssued1994-07Revised2006-12SupersedingJ1939-21APR2001DataLinkLayerRATIONALEThisSAERecommendedPracticerevisionincorporateschangestotheassignedSAEReservedBittobetheExtendedDataPageBit,Acknowledgementsections,thenewproprietaryA2PGN(PGN126720)andincludesnewSPNassignmentsinAppendixD.The'Reserved'bitofthe29-bitofJ1939headerhasbeendefinedasthe'ExtendedDataPage'(EDP)bit.TheJ1939SubcommitteehasconcernstheremightbeexistinganddevelopingcomponentsforJ1939thatdon'tverifytheReserved/EDPbitiszero(0)beforeprocessingthe29-bitheaderpertheJ1939-21structure.ItisimportantthatexistingandfutureJ1939applicationsexaminethevaluesoftheEDPandDPbitsbeforeinterpretingtheremaining24bitsperthePDUFormat(PF),PDUSpecific(PS),andSourceAddress(SA)structurespecifiedinJ1939-21.BackwardcompatibilityismaintainedduringthischangebyspecifyingtheExtendedDataPagebitvalueofzeroforallexistingJ1939PGNs.Priortothisfunctionalchange,J1939-21requiredtheReservedbittobesettozero(0)inallJ1939PGNDataFrameheaders.FOREWORDThisseriesofSAERecommendedPracticeshavebeendevelopedbytheTruckandBusControlandCommunicationsNetworkSubcommitteeoftheTruckandBusElectricalandElectronicsCommittee.Theobjectivesofthesubcommitteearetodevelopinformationreports,recommendedpractices,andstandardsconcernedwiththerequirements,design,andusageofdevicesthattransmitelectronicsignalsandcontrolinformationamongvehiclecomponents.TheusageoftheseRecommendedPracticesisnotlimitedtotruckandbusapplications;otherapplicationsmaybeaccommodatedwithimmediatesupportbeingprovidedforconstructionandagriculturalequipment,andstationarypowersystems.TheseSAERecommendedPracticesareintendedasaguidetowardstandardpracticeandaresubjecttochangesoastokeeppacewithexperienceandtechnicaladvances.ThisdatalinklayerisusedforallSAEJ1939applications.ItisthecharacteristicthatiscommonacrossallSAEJ1939applications.__________________________________________________________________________________________________________________________________________SAETechnicalStandardsBoardRulesprovidethat:“ThisreportispublishedbySAEtoadvancethestateoftechnicalandengineeringsciences.Theuseofthisreportisentirelyvoluntary,anditsapplicabilityandsuitabilityforanyparticularuse,includinganypatentinfringementarisingtherefrom,isthesoleresponsibilityoftheuser.”SAEreviewseachtechnicalreportatleasteveryfiveyearsatwhichtimeitmaybereaffirmed,revised,orcancelled.SAEinvitesyourwrittencommentsandsuggestions.Copyright©2006SAEInternationalAllrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystemortransmitted,inanyformorbyanymeans,electronic,mechanical,photocopying,recording,orotherwise,withoutthepriorwrittenpermissionofSAE.TOPLACEADOCUMENTORDER:Tel:[phone](insideUSAandCanada)Tel:[phone](outsideUSA)Fax:[phone]Email:[e-mail]:(R)...........................................................................................................................................45.TechnicalRequirements...............................................................................................................................55.1Message/FrameFormat................................................................................................................................55.1.1SAEJ1939MessageFrameFormat(“CAN2.0B”ExtendedFrameFormat)(R)........................................65.1.2ParameterGroupNumber(PGN).................................................................................................................65.1.3SAEJ1939Supportof“CAN2.0B”StandardFrameFormatMessages....................................................105.2ProtocolDataUnit(PDU)............................................................................................................................115.2.1