NoreproductionornetworkingpermittedwithoutlicensefromIHS

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SURFACEVEHICLERECOMMENDEDPRACTICE

J1939-11

REV.OCT1999

Issued 1994-12

Revised 1999-10

SupersedingJ1939/11DEC1994

SubmittedforrecognitionasanAmericanNationalStandard

PhysicalLayer,250Kbits/s,TwistedShieldedPair

Foreword—ThisseriesofSAERecommendedPracticeshavebeendevelopedbytheTruckandBusControlandCommunicationsNetworkSubcommitteeoftheTruckandBusElectricalCommittee.Theobjectivesofthesubcommitteearetodevelopinformationreports,recommendedpractices,andstandardsconcernedwiththerequirementsdesignandusageofdeviceswhichtransmitelectronicsignalsandcontrolinformationamongvehiclecomponents.Theusageoftheserecommendedpracticesisnotlimitedtotruckandbusapplications.Otherapplicationsmaybeaccommodatedwithimmediatesupportbeingprovidedforconstructionandagriculturalequipment,andstationarypowersystems.

TheseSAERecommendedPracticesareintendedasaguidetowardstandardpracticeandaresubjecttochangetokeeppacewithexperienceandtechnicaladvances.

TABLEOFCONTENTS

Scope 2

References 3

ApplicablePublications 3

SAEPublications 3

ISOPublication 3

MilitaryPublication 3

RelatedPublication 3

ISOPublications 3

NetworkPhysicalDescription 3

PhysicalLayer 3

PhysicalMedia 3

DifferentialVoltage 4

BusLevels 4

BusLevelsDuringArbitration 4

CommonModeBusVoltageRange 4

BusTermination 4

InternalResistance 4

DifferentialInternalResistance 4

InternalCapacitance 4

DifferentialInternalCapacitance 4

BitTime 4

InternalDelayTime 6

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SAETechnicalStandardsBoardRulesprovidethat:“ThisreportispublishedbySAEtoadvancethestateoftechnicalandengineeringsciences.Theuseofthisreportisentirelyvoluntary,anditsapplicabilityandsuitabilityforanyparticularuse,includinganypatentinfringementarisingtherefrom,isthesoleresponsibilityoftheuser.”

SAEreviewseachtechnicalreportatleasteveryfiveyearsatwhichtimeitmaybereaffirmed,revised,orcancelled.SAEinvitesyourwrittencommentsandsuggestions.

Copyright1999SocietyofAutomotiveEngineers,Inc.

A

CopyrightSAEInternationalllrightsreserved. PrintedinU.S.A.

ProvidedbyIHSunderlicensewithSAE

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NotforResale

CopyrightSAEInternational

ProvidedbyIHSunderlicensewithSAE

NoreproductionornetworkingpermittedwithoutlicensefromIHS

SAEJ1939-11RevisedOCT1999

3.14 CANBitTimingRequirements 8

FunctionalDescription 9

ElectricalSpecification 9

ElectricalData 9

ElectronicControlUnit 9

AbsoluteMaximumRatings 10

DCParameters 10

ACParameters 11

BusVoltages—Operational 11

ElectrostaticDischarge(ESD) 11

ExamplePhysicalLayerCircuits 11

PhysicalMediaParameters 11

BusLine 12

Topology 12

TerminatingResistor 13

ShieldTermination 13

ConnectorSpecifications 14

ConnectorElectricalPerformanceRequirements 14

ConnectorMechanicalRequirements 15

ConformanceTests 16

RecessiveOutputoftheECUs 16

InternalResistanceofCAN_HandCAN_L 17

InternalDifferentialResistance 17

RecessiveInputThresholdofanECU 18

DominantOutputofanECU 18

DominantInputThresholdofanECU 19

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InternalDelayTime 19

DiscussionofBusFaults 20

LossofConnectiontoNetwork 20

NodePowerorGroundLoss 20

UnconnectedShield 20

OpenandShortFailures 20

Notes 22

MarginalIndicia 22

AppendixAExamplePhysicalLayerCircuits 23

Example1PhysicalLayer 23

Example2PhysicalLayer 23

Example3PhysicalLayer 25

AppendixBRecommendedCableTerminationProcedure 26

AppendixCRecommendedCableSpliceProcedure 27

AppendixDRecommendedCableRepairProcedure 29

Scope—TheseSAERecommendedPracticesareintendedforlight-andheavy-dutyvehicleson-oroff-roadaswellasappropriatestationaryapplicationswhichusevehiclederivedcomponents(e.g.,generatorsets).Vehiclesofinterestincludebutarenotlimitedto:on-andoff-highwaytrucksandtheirtrailers;constructionequipment;andagriculturalequipmentandimplements.

SAEJ1939-11RevisedOCT1999

Thepurposeofthesedocumentsistoprovideanopeninterconnectsystemforelectronicsystems.Itistheintentionofthesedocumentstoallowelectronicdevicestocommunicatewitheachotherbyprovidingastandardarchitecture.

References—GeneralinformationregardingthisseriesofrecommendedpracticesisfoundinSAEJ1939.

ApplicablePublications—Thefollowingpublicationsformapartofthisspecificationtotheextentspecifiedherein.Unlessotherwiseindicated,thelatestissueofSAEpublicationsshallapply.

SAEPUBLICATIONS—AvailablefromSAE,400CommonwealthDrive,Warrendale,PA15096-0001.

(R)

(R)

SAEJ1113/13Electromagnetic Compatibility Measurement Procedure for Vehicle ComponentsPart13ImmunitytoElectrostaticDischarge

SAEJ1128—Low-TensionPrimaryCable

SAEJ1939(Draft)RecommendedPracticeforaSerialControlandCommunicationVehicleNetwork

ISOPublication—AvailablefromANSI,11West42ndStreet,NewYork,NY10036-8002.

(R) ISO6722—Roadvehicles—Unscreenedlow-tensioncables

MilitaryPublication—AvailablefromDODSSP,SubscriptonServicesDesk,Building4D,700RobinsAvenue,Philadelphia,PA19111-5094.

(R) MIL-C-85485—Cable,Electric,FilterLine

RelatedPublication—Thefollowingpublicationisprovidedforinformationpurposesonlyandisnotarequiredpartofthisdocument.

ISOPUBLICATION—AvailablefromANSI,11West42ndStreet,NewYork,NY10036-8002.

ISO11898RoadvehiclesInterchangeofdigitalinformationControllerAreaNetwork(CAN)forhighspeedcommunication.

NetworkPhysicalDescription

PhysicalLayer—ThephysicallayerisarealizationofanelectricalconnectionofanumberofECUs(ElectronicControlUnits)toanetwork.ThetotalnumberofECUswillbelimitedbyelectricalloadsonthebusline.ThismaximumnumberofECUsisfixedto30,onagivensegment,duetothedefinitionoftheelectricalparametersgiveninthepresentspecification

PhysicalMedia—Thisdocumentdefinesaphysicalmedianofshieldedtwistedpair.These2wireshaveacharacteristicimpedanceof120andaresymmetricallydrivenwithrespecttotheelectricalcurrents.ThedesignationsoftheindividualwiresareCAN_HandCAN_L.ThenamesofthecorrespondingpinsoftheECUsarealsodenotedbyCAN_HandCAN_L,respectively.ThethirdconnectionfortheterminationoftheshieldisdenotedbyCAN_SHLD.

DifferentialVoltage—ThevoltagesofCAN_HandCAN_LrelativetogroundofeachindividualECUaredenotedbyVCAN_HandVCAN_L.ThedifferentialvoltagebetweenVCAN_HandVCAN_LisdefinedbyEquation1:

Vdiff=VCAN_HVCAN_L (Eq.1)

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SAEJ1939-11RevisedOCT1999

BusLevels—Thebuslinescanhaveoneofthetwologicalstates,recessiveordominant(seeFigure1).Intherecessivestate,VCAN_HandVCAN_Larefixedtoameanvoltagelevel.Vdiffisapproximatelyzeroonaterminatedbus.Therecessivestateistransmittedduringbusidleorarecessivebit.

Thedominantstateisrepresentedbyadifferentialvoltagegreaterthanaminimumthreshold.Thedominantstateoverwritestherecessivestateandistransmittedduringadominantbit.

BusLevelsDuringArbitration—AdominantandrecessivebitimposedonthebuslinesduringagivenbittimebytwodifferentECUswillresultinadominantbit.

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FIGURE1PHYSICALBITREPRESENTATION

CommonModeBusVoltageRange—ThecommonmodebusvoltageisdefinedastheboundaryvoltagelevelsofCAN_HandCAN_L,measuredwithrespecttotheindividualgroundofeachECU,forwhichproperoperationisguaranteedwhenallECUsareconnectedtothebusline.

(R)3.7BusTermination—ThebuslineiselectricallyterminatedateachendwithaloadresistordenotedbyRL.RLshallnotbelocatedwithinanECUbecausethebuswillloseterminationifoneoftheseECUsisdisconnected(seeFigure2).(Alsosee5.2.3forresistorcharacteristics.)

InternalResistance—Theinternalresistance,Rin,ofanECUisdefinedastheresistanceseenbetweenCAN_H(orCAN_L)andgroundduringtherecessivestate,withtheECUdisconnectedfromthebusline(seeFigure3).

DifferentialInternalResistance—Thedifferentialinternalresistance,Rdiff,isdefinedastheresistanceseenbetweenCAN_HandCAN_Lduringtherecessivestate,withtheECUdisconnectedfromthebusline(seeFigure4).

InternalCapacitance—Theinternalcapacitance,Cin,ofanECUisdefinedasthecapacitanceseenbetweenCAN_H(orCAN_L)andgroundduringtherecessivestate,withtheECUdisconnectedfromthebusline(seeFigure3).

DifferentialInternalCapacitance—Thedifferentialinternalcapacitance,Cdiff,ofanECUisdefinedasthecapacitanceseenbetweenCAN_HandCAN_Lduringtherecessivestate,withtheECUdisconnectedfromthebusline(seeFigure4).

BitTime—Thebittime,tB,isdefinedasthedurationofonebit(seeFigure5).Busmanagementfunctionsexecutedwithinthisbittime,suchasECUsynchronizationbehavior,networktransmissiondelaycompensation,andsamplepointpositioning,aredefinedbytheprogrammablebittiminglogicoftheCANprotocolIC(IntegratedCircuit).Thebittimeforthisdocumentis4μscorrespondingto250Kbit/s.

VariousnamesforthebitsegmentsareusedbysuppliersofCANprotocolICsanditispossiblethattwobitsegmentsaredefinedasone.

SAEJ1939-11RevisedOCT1999

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FIGURE2PHYSICALLAYERFUNCTIONAL

SAEJ1939-11RevisedOCT1999

FIGURE3ILLUSTRATIONOFINTERNALCAPACITANCEANDRESISTANCEOFANECUINTHERECESSIVESTATE

FIGURE4ILLUSTRATIONOFDIFFERENTIALINTERNALCAPACITANCEANDRESISTANCEOFANECUINTHERECESSIVESTATE

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FIGURE5PARTITIONOFTHEBIT

SYNCSEGThispartofthebittimeisusedtosynchronizethevariousECUsonthebus.Anedgeisexpectedwithinthisbitsegment.

PROPSEGThispartofthebittimeisusedtocompensateforthephysicaldelaytimeswithinthenetwork.ThesedelaytimesarecausedbythepropagationtimeofthebuslineandtheinternaldelaytimeoftheECUs.

PHASESEG1,PHASESEG2ThesePhase-Buffer-Segmentsareusedtocompensateforphase-errorsandcanbelengthenedorshortenedbyresynchronization.

Sample-PointTheSample-Pointisthepointoftimeatwhichthebuslevelisreadandinterpretedasthevalueofthatrespectivebit.ItslocationisattheendofPHASE_SEG1.

SAEJ1939-11RevisedOCT1999

InternalDelayTime—TheinternaldelaytimeofanECU,tECU,isdefinedasthesumofallasynchronousdelaysthatoccuralongthetransmissionandreceptionpathoftheindividualECUs,relativetothebittiminglogicunitoftheprotocolIC.Formoredetails,seeFigure6.

SynchronizationHardSynchronizationandResynchronizationarethetwoformsofsynchronization.Theyobeythefollowingrules:

OnlyoneSynchronizationwithinonebittimeisallowed.

AnedgewillbeusedforSynchronizationonlyifthevaluedetectedatthepreviousSamplePoint(previouslyreadbusvalue)differsfromthebusvalueimmediatelyaftertheedge.

HardSynchronizationisperformedduringsaidedgewheneverthereisa‘recessive’to‘dominant’edge.

Allother‘recessive’to‘dominant’edgesfulfillingrules1and2willbeusedforResynchronizationwiththeexceptionthatatransmitterwillnotperformResynchronizationasaresultofa‘recessive’to‘dominant’edgewithapositivePhaseErrorifonly‘recessive’to‘dominant’edgesareusedforResynchronization.

SynchronizationJumpWidth(SJW)AsaresultofSynchronizationPHASE_SEG1maybelengthened

orPHASE_SEG2maybeshortened.TheamountoflengtheningorshorteningofthePhaseBufferbitSegmentshasanupperboundgivenbytheSynchronizationJumpWidth.TheSynchronizationJumpWidthislessthanorequaltoPHASE_SEG1.

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SAEJ1939-11RevisedOCT1999

FIGURE6TIMERELATIONSHIPBETWEENBITTIMINGLOGICOFECUAANDBDURINGARBITRATION

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SAEJ1939-11RevisedOCT1999

CANBitTimingRequirements—Itisnecessarytoensurethatareliablenetworkcanbeconstructedwithcomponentsfrommultiplesuppliers.Withoutanybittimingrestrictions,differentdevicesmaynotbeabletoproperlyreceiveandinterpretvalidmessages.Undercertainnetworkconditionsitmayalsobepossibleforaparticulardevicetohaveunfairaccesstothenetwork.Inaddition,itmakesnetworkmanagement(systemdiagnostics)muchmoredifficult.CANchipsuppliersalsorecommendthatalldevicesonagivennetworkbeprogrammedwiththesamebittimingvalues.

(R) AllCANICsdividethebittimeintosmallersectionsdefinedastq(timequantum).FormostCANICs1tq=250ns(witha16MHzclock)(determinedbyoscillatorfrequencyandbaudrateprescaler).

(R) Thereforespecificvaluesforthebittimingregistersneedtobedefinedtoensurethatareliablenetworkexistsforallnodesbasedonthebesttradeoffsbetweenpropagationdelayandclocktolerance.NotethattherearesomedifferencesinbitsegmentdefinitionbetweenmanufacturersofCANdevices.

(R) Itisrecommendedthatatqbeselectedwhichpermitsthesamplepoint(seeFigure5)tobelocatedasclosetobutnotlaterthan7/8ofabittime(0.875x4uS=3.5uS).Thisprovidesthebesttradeoffbetweenpropagationdelayandclocktolerance.

(R) ThefollowingvaluesarerecommendedfortypicalcontrollerICsrunningatstandardclockfrequencies.Atotherfrequencies,differentvaluesmayhavetobeselectedtomaintainthesamplepointascloseaspossiblebutnotlaterthanthepreferredtime.

(R) 16MHz

samplepoint=0.875tbtq=250ns(16tq/bit)tsync=250ns(1tq)TSEG1=3.25μs(13tq)

TSEG2=500ns(2tq)

(R) 20MHz

samplepoint=0.85tbtq=200ns(20tq/bit)

tsync=200ns(1tq)

TSEG1=3.2μs(16tq)

TSEG2=600ns(3tq)

(R) SJW=1tq(SJWisapartofTSEG1andTSEG2)

TotalBitTime=TSEG1+TSEG2+Tsyncseg=13+2+1=16tq=4μs(Examplefor16MHzclock)

PROP_SEG+PHASE_SEG1=TSEG1PHASE_SEG2=TSEG2,

SYNC_SEG=SYNC_SEG

ThisselectionforthebittimingregistersgenerallyrequirestheuseofCrystalOscillatorsatallnodessothattheclocktolerancegiveninTable1canbeachieved.

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SAEJ1939-11RevisedOCT1999

TABLE1ACPARAMETERSOFANECUDISCONNECTEDFROMTHEBUSLINE

Parameter

Symbol

Min

Nom

Max

Unit

Conditions

Bittime(1)

tB

3.998

4.000

4.002

μs

250Kbit/s

InternalDelayTime(2)

tECU

0.0

0.9

μs

InternalCapacitance(3)

Cin

0

50

100

pF

250Kbit/sforCAN_HandCAN_LrelativetoGround

DifferentialInternalCapacitance(3)

Cdiff

0

25

50

pF

AvailableTime(4)

tavail

2.5

μs

40mbuslength

SignalRise,FallTime(5)

tR,tF

200

500

ns

measuredfrom10%to90%

ofthesignal

Includinginitialtolerance,temperature,aging,etc.

ThevalueoftECUhastobeguaranteedforadifferentialvoltageofVdiff=1.0VforatransitionfromrecessivetodominantandofVdiff=0.5Vforatransitionfromdominanttorecessive.Withthebittimingfromtheexampleofnote1,aCAN-Interfacedelayof500nsispossible(controllernotincluded)withareserveofabout300ns.Thisallowsslowerslopes(R3andR4inFiguresA1andA2)andinputfiltering(R5,R6,C1,C2inFiguresA1andA2).ItisrecommendedtousethisfeatureduetoEMC.

Theminimalinternaldelaytimemaybezero.Themaximumtolerablevalueisdeterminedbythebittimingandthebusdelaytime.

Inadditiontotheinternalcapacitancerestrictionsabusconnectionshouldalsohaveaninductanceaslowaspossible.TheminimumvaluesofCandCmay

in diff

be0,themaximumtolerablevaluesaredeterminedbythebittimingandthenetworktopologyparameterslandd(seeTable8).ProperfunctionalityisguaranteedifoccurringcableresonantwavesdonotsuppressthedominantdifferentialvoltagelevelbelowVdiff=1VanddonotincreasetherecessivedifferentialvoltagelevelaboveVdiff=0.5VateachindividualECU(seeTables3and4).

TheavailabletimeresultsfromthebittimingunitoftheprotocolIC.Forexample,thistimeinmostcontrollerICscorrespondstoTSEG1.DuetomissynchronizationitispossibletolosethelengthofSJW.Sotheavailabletime(tavail)withonemissynchronizationisTSEG1-SJWms.Atqtimeof250nsandSJW=1tq,TSEG1=13tq,TSEG2=2tqresultsintavail=3.00s.

TheloadontheECUforthepurposeofthisparametershouldbe60ohmsbetweenCAN_HandCAN_Linparallelwith200pfofcapacitance

FunctionalDescription—AsshowninFigure2,thelinearbuslineisterminatedwithaloadresistorRLoneachend.Theseresistorssuppressreflections.

ThebusisintherecessivestateifthebustransmittersofallECUsonthebusareswitchedoff.Inthiscase,themeanbusvoltageisgeneratedbythepassivebiasingcircuitinallECUsonthebus.InFigure2thisisrealizedbytheresistornetworkthatdefinesthereferenceforthereceiveoperation.

Adominantbitissenttothebuslineifthebusdrivercircuitofatleastoneunitisswitchedon.Thisinducesacurrentflowthroughtheterminatingresistors,andconsequently,adifferentialvoltagebetweenthetwowires.Thedominantandrecessivestatesarepassedbyaresistornetworkwhichtransformsthedifferentialvoltagesofthebuslinetocorrespondingrecessiveanddominantvoltagelevelsatthecomparatorinputofthereceivingcircuitryfordetection.

ElectricalSpecification

ElectricalData—TheparameterspecificationsinthesetablesmustbefulfilledthroughouttheoperatingtemperaturerangeofeveryECU.Theseparametersallowuptoamaximumof30ECUstobeconnectedtoagivenbussegment.

ELECTRONICCONTROLUNIT—ThelimitsgivenintheTables1to4,applytotheCAN_HandCAN_LpinsofeachECU,withtheECUdisconnectedfromthebusline(seeSection6).

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SAEJ1939-11RevisedOCT1999

TABLE2LIMITSOFVCAN_HANDVCAN_LOFANECUDISCONNECTEDFROMTHEBUSLINEFORNOMINALBATTERYVOLTAGESOF12VAND24V

Parameter Symbol Min Nom Max Unit Conditions

Max.Voltage VCAN_HVCAN_L

3.0

3.0

16.0

16.0

V nominalbatteryvoltage12VV

Max.Voltage

VCAN_HVCAN_L

3.0

3.0

32.0

32.0

V nominalbatteryvoltage24VV

AbsoluteMaximumRatings—ThelimitsgiveninTable2aretheabsolutemaximumDCvoltageswhichcanbeconnectedtothebuslineswithoutdamagetotransceivercircuits.Althoughthelinkisnotguaranteedtooperateattheseconditions,thereisnotimelimit(operatingCANICswillgo“errorpassive”afteraperiodoftime).

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DCParameters—Tables3and4definetheDCparametersfortherecessiveanddominantstates,respectively,ofanECUdisconnectedfromthebus.

TABLE3DCPARAMETERSFORTHERECESSIVESTATEOFANECUDISCONNECTEDFROMTHEBUSLINERECESSIVESTATE

Parameter Symbol

Min

Nom

Max

Unit

Conditions

BusVoltage VCAN_H

2.0

2.5

3.0

V

noload

VCAN_L

2.0

2.5

3.0

V

OutputBehavior

DifferentialVoltageOutputBehavior Vdiff_or

1200

50

mV

noload

DifferentialInternalResistance Rdiff

10

100

k

noload

InternalResistance(1) Rin

5

15

k

noload

InputRange Vdiff 1.0

0.5

V

(2)(3)(4)

InordertogeneratesymmetricalwaveformsandminimizeEMIradiation,RinofCAN_HandCAN_Lshouldhavealmostthesamevalue.Thedeviationhastobelessthan5%relativetoeachother.

Theequivalentofthetwoterminatingresistorsinparallel(60)isconnectedbetweenCAN_HandCAN_L.

ReceptionmustbeensuredwithinthecommonmodevoltagerangedefinedinTable5andTable6,respectively.

AlthoughVdiff<–1.0Visonlypossibleduringfaultconditionsitshouldbeinterpretedasrecessive.

TABLE4DCPARAMETERSFORTHEDOMINANTSTATEOFANECUDISCONNECTEDFROMTHEBUSLINEDOMINANTSTATE

Parameter Symbol Min Nom Max Unit Conditions

BusVoltageOutputBehavior

VCAN_H

3.0

3.5

5.0

V (1)

VCAN_L

0.0

1.5

2.0

V

DifferentialVoltageOutputBehavior

Vdiff_ld

1.5

2.0

3.0

V (1)

InputRange

Vdiff

1.0

5.0

V (1)(2)

Theequivalentofthetwoterminatingresistorsinparallel(60)isconnectedbetweenCAN_HandCAN_L.

ReceptionmustbeensuredwithinthecommonmodevoltagerangedefinedinTables5and6,respectively.

SAEJ1939-11RevisedOCT1999

TABLE5BUSVOLTAGEPARAMETERSFORTHERECESSIVESTATEWITHALLECUsCONNECTEDTOTHEBUSLINERECESSIVESTATE

Parameter Symbol Min Nom Max Unit Conditions

Voltageonthebusline VCAN_L 0.1 2.5 4.5 V measuredwithrespecttogroundof

eachECU

Differential

Vdiff

400

0

12

mV

measuredateachECUconnectedto

BusVoltage(1)

thebusline

ThedifferentialbusvoltageisdeterminedbytheoutputbehaviorofallECUsduringtherecessivestate.Therefore,Vdiffisapproximatelyzero(seeTable3).TheminimumvalueisdeterminedbytherequirementthatasingletransmittermustbeabletorepresentadominantbitbyaminimumvalueofVdiff=1.2V.

TABLE6BUSVOLTAGEPARAMETERSFORTHEDOMINANTSTATEWITHALLECUsCONNECTEDTOTHEBUSLINEDOMINANTSTATE

Parameter Symbol Min Nom Max Unit Conditions

VoltageonBus(1) VCAN_H

3.5

7.0

V

measuredwithrespect

VCAN_L 2.0

1.5

toground

ofeachECU

Differential Vdiff 1.2

2.0

3.0

V

Measuredateach

BusVoltage(2)

ECUconnectedtothe

busline

5.0

V

duringarbitration

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TheminimumvalueofVCAN_HisdeterminedbytheminimumvalueofVCAN_LplustheminimumvalueofVdiff.ThemaximumvalueofVCAN_LisdeterminedbythemaximumvalueofVCAN_HminusthevalueofVdiff.

ThebusloadincreasesasECUsareaddedtothenetwork,duetoRdiff.Consequently,Vdiffdecreases.TheminimumvalueofVdiffdeterminesthenumberofECUsallowedonthebus.ThemaximumvalueofVdiffisdefinedbytheupperlimitduringarbitration.ThismaximumvalueofVdiffforsingleoperationmustnotexceed3V.

ACParameters—Table1definestheACParameterrequirementsoftheECUs.

(R)5.1.2BUSVOLTAGES—OPERATIONAL—TheparametersspecifiedinTables5and6applywhenallECUs(between2and30)areconnectedtoacorrectlyterminatedbusline.ThemaximumallowablegroundoffsetbetweenanyECUsonthebusis2V.Thevoltageextremesassociatedwiththisoffsetwouldoccurinthedominantstate(seeTable6).

5.1.3ELECTROSTATICDISCHARGE(ESD)—CAN_HandCAN_LshouldbetestedwhiledisconnectedfromthebuslineaccordingtoSAEJ1113/13forESDusing15kV.

(R) 5.1.4 EXAMPLEPHYSICALLAYERCIRCUITS—Therearemanypossiblediscreteandintegratedphysicallayercircuitswhichmeetthepreviousrequirement.ExamplesofimplementationsareshowninAppendixA.

PhysicalMediaParameters—Thefollowingsectionsdescribethecharacteristicsofthecable,termination,andtopologyofthenetwork.(SeeTable7.)

SAEJ1939-11RevisedOCT1999

(R) TABLE7PHYSICALMEDIAPARAMETERSFORTWISTEDSHIELDEDCABLE

Parameter

Symbol

Min

Nom

Max

Unit

Conditions

Impedance

Z

108

120

132

Threemetersamplelengthmeasuredat

1Mhzbetweenthetwosig.wires,with

shieldgrounded,usingopen/shortmethod.

SpecificResistance

rb

0

25

50

m/m

measuredat20°C(1)

SpecificLineDelay

tp

5.0

ns/m

67%Vp(2)

Specific

cb

0

40

75

pF/m

Betweenconductors

Capacitance

cs 0

70 110

pF/m

Conductortoshield

Cablesize (3)

0.5mm2Conductor(20AWG)

Wireinsuldia.Cablediameter

0.8mm2Conductor(18AWG)

Wireinsuldia.Cablediameter

ShieldEffectiveness

ac

dcidc

ac

dcidc

0.508

mm2

(4)

2.23

3.05

mm

6.0

8.5

mm

0.760

mm2

(4)

2.5

3.5

mm

8.5

11.0

mm

200 225 m/m Surfacetransferimpedanceupto1MHz

TestmethodperMIL-C-85485

TemperatureRange C –40 +125 °C Heataging:3000hoursperISO6722,

Testwithamandrel4-5xdiameterofcable.(5)

CableBendRadius r 4xdiaof

cable

mm 90degreebendradiuswithoutcableperformanceorphysicaldegradation

ThedifferentialvoltageonthebuslineseenbyareceivingECUdependsonthelineresistancebetweenitandthetransmittingECU.Therefore,thetotalresistanceofthesignalwiresislimitedbythebuslevelparametersofeachECU.

Theminimumdelaytimebetweentwopointsofthebuslinemaybezero.Themaximumvalueisdeterminedbythebittimeandthedelaytimesofthetransmittingandreceivingcircuitry.

Otherconductorsizesavailable.ComponentinsulationdimensionsmaybelargerthanthosespecifiedinSAEJ1128.Designengineersshouldensurecompatibilitybetweencables,connectorsandcontacts

MeetperformancerequirementsofSAEJ1128fortypesGXLorSXL(includesdrainwirewhereapplicable)

125°CorperOEMspecification

BUSLINE—ThebuslineconsistsofaCAN_H,CAN_LandCAN_SHLDconductors.TheCAN_HshouldbeyellowincolorwhiletheCAN_Lshouldbegreen.Inaddition,thecablemustmeetthefollowingminimumrequirements.

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(R)5.2.2TOPOLOGY—Thewiringtopologyofthisnetworkshouldbeascloseaspossibletoalinearstructureinordertoavoidcablereflections.Inpractice,itmaybenecessarytoconnectshortcablestubstoamainbackbonecable,asshowninFigure7.Tominimizestandingwaves,nodesshouldnotbeequallyspacedonthenetworkandcablestublengths,dimensionSinFigure7,shouldnotallbethesamelength.ThedimensionalrequirementsofthenetworkareshowninTable8.

SAEJ1939-11RevisedOCT1999

FIGURE7WIRINGNETWORKTOPOLOGY

(R) TABLE8NETWORKTOPOLOGYPARAMETERS

Parameter

Symbol

Min

Nom

Max

Unit

Conditions

BusLength

L

0

40

m

notincludingcablestubs

CableStubLength(1)

S

0

1

m

Note1

Node

d

0.1

40

m

Distance

Minimum

d0

0

m

RLshallnotbelocatedwithin

DistancefromRL

anECU

1.Thecablestublengthforthediagnosticconnectoris0.66mmaximumforthevehicleand0.33mmaximumfortheoff-boarddiagnostictool.

5.2.3 TERMINATINGRESISTOR—Eachendofthemain‘backbone’ofthelinearbusmustbeterminatedwithanappropriateresistancetoprovidecorrectterminationoftheCAN_HandCAN_Lconductors.ThisterminationresistanceshouldbeconnectedbetweentheCAN_HandCAN_Lconductors.TheterminationresistanceshouldmeetthecharacteristicsspecifiedinTable9.

TABLE9TERMINATINGRESISTORPARAMETERS

Parameter Symbol

Min

Nom

Max

Unit

Conditions

Resistance RL

110

120

130

minimumpowerdissipation400mW(1)

Inductance

1

μh

1.Assumesashortof16VtoV

CAN_H

5.2.4 SHIELDTERMINATION—Theshieldshouldbeterminatedbyawireconductoranddirectlygroundedatonlyonepoint.

Generalguidelines(inorderofimportance)fordirectterminationoftheshieldare:

Connecttothepointofleastelectricalnoise

Usethelowestimpedanceconnectionpossible

Theclosestconnectiontothecenterofthenetworkshouldbeused.

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SAEJ1939-11RevisedOCT1999

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