Comparing Bus Solutions (Rev. C)

1 1 SLLA067C March2000 RevisedAugust2017 SubmitDocumentationFeedbackCopyright 2000 2017,TexasInstrumentsIncorporatedCompari ngBus SolutionsApplicationReportSLLA067C March2000 RevisedAugust2017 ComparingBus SolutionsFalk Alicke,MatthiasFeulner,FrankDehmelt,Anku rVerma,and G. stronginterestin this applicationreportpromptedthis additionto the changesandupdatesmadethroughoutthesesect ions,this editionalsodiscussesLocalInterconnectNet work(LIN),USB-On-the-Go,DisplayPort,digi talisolators,and applicationreportservesas a referencetoolfor findingthe mostappropriatedatabus solutionfor today s givesanoverviewof the differentbus use manydifferentsolutionsto solvethe task is to identifythe optimumsolutionfor applicationreportmakesit easierfor designersto do this.

2 It has sectionson datatransmissionfundamentals,dataline driversandreceivers,datalinks, electricalproperties,applicability,and featuresof (BTL).. (CML).. (CAN).. (ECL)and PositiveECL(PECL).. (GTL).. (GTLP).. (LIN).. (LVDM).. (SSTL).. (RS-232).. (RS-422).. (RS-485).. (LVDS).. (M-LVDS).. BackplaneApplications(FireWire).. March2000 RevisedAugust2017 SubmitDocumentationFeedbackCopyright 2000 2017,TexasInstrumentsIncorporatedCompari ngBus (USBOTG).. (CDC).. of Paralleland an Open-CollectorBus SystemUsingBTL an Open-CollectorBus SpacingWithGTLPM ediumand ,ClassII of / Type2 Cardfor Bus SystemWith8 PCI TieredStar March2000 RevisedAugust2017 SubmitDocumentationFeedbackCopyright 2000 2017.

3 TexasInstrumentsIncorporatedComparingBus SignalsPassThroughBetweenCircuit1 and CreepageDistancefor a Measuringthe ClearanceDistancefor a of DeviceList FeatureList of AdvancedSystemLogicby DeviceList DeviceList DeviceList IEEE1284 DeviceList for DeviceList and Link (dB).. LVDSSerDesand FlatLink IEEE1394 Link LayerDeviceList (PC)..5334 Top IEEE1394 IntegratedDeviceList (PC)..5335 Top IEEE1394 IntegratedDeviceList (Non-PC)..5436 Top IEEE1394 Link LayerDeviceList (Non-PC)..5437 Top DeviceList - PCI March2000 RevisedAugust2017 SubmitDocumentationFeedbackCopyright 2000 2017,TexasInstrumentsIncorporatedCompari ngBus Solutions39 ,SCOPE,FlatLink,MicroStarJunior,OMAPare trademarksof is a trademarkof Intel othertrademarksare the propertyof today s information-hungryage,transmittingdatase veralinchesbetweencomputermemoryanddispl ayscreenis just as criticalas sendingit halfwayaroundthe meettheseincreasinglydemandingdatatransm issionneeds.

4 TexasInstrumentshas combinedits expertisein high-speeddigitaland analogtechnologiesto constantlyextendthe performanceand capabilityof applicationreportprovidesthe readerwith an overviewof wireddata-bussystemsand providesinsightinto whichstandardor bus configurationbest suitsa designer s ,theirtechnicalfeatures,and the productsthat TI offersfor eachofthesestandardapplications,the fundamentaldifferencesof the basicbus structuresmustbe the purposesof this report,productsare dividedinto dataline driversand receivers,datalinks,anddatasignalconditi onersor driversand receiversgenerateand receivethe electricalsignalsovercablesor productsarrangedatafor transmissionand disassembleitfor translatorsmodifydatasignalsfor DifferentialTransmissionThe two basicformsof datatransmissioncircuitsare single-endedand the single-endedorunbalancedcircuitof Figure1, the voltagedifferencebetweenthe signalline and commonlocalgrounddeterminesthe bus the Figure2 differentialor balancedcircuit.

5 The voltagedifferencebetweentwo complementarysignallinesdeterminesthe bus advantagesand presentsthe electricalschematicdiagramof a single-endedtransmissioncircuitand the noisesourcesVNand VGthat directlyadd to the signalvoltage,VO. This makesthe single-endedcircuitsusceptibleto complementarysignal(as in differential)cancelsthefieldscreatedby the single-endedsignal,it emissionsrelegatesingle-endedinterfacest o low signalingratesand ,the single-endedinterfaceline driver,receiver,and interconnectioncostsare oftenless thanthoseof EndedDRDifferentialrDriverReceiverVOBVOA VIBVIAVIDS ignal ReturnVNVNVGV = V+ V + VV = V+ V + VV - V = V- V= VIAOANGIBOBNGIAIBOAOBIDVOVGD riverReceiverSignal LineSignal ReturnVN+-V = V + V = VIONG+ March2000 RevisedAugust2017 SubmitDocumentationFeedbackCopyright 2000 2017,TexasInstrumentsIncorporatedCompari ngBus SolutionsFigure1.

6 Single-EndedTransmissionCircuitModelFigu re2 showsthe electricalschematicdiagramof a differentialtransmissioncircuitin whichnoisesourcesVNand VGadd to eachsignalline and are commonto differentialreceivermeasuresthe differencebetweenthe two linesand rejectsthe commonvoltageof the usedwithcloselycoupledlines,the complementarysignalscanceleachother s electromagneticfields,resultinginhigh immunityand low immunityto externalnoiseinfluenceand the low radiatedemissionsmakedifferentialsignali nga goodchoicewhenrelativelyhigh signalingratesand long distanceare requiredin electricallynoisy,or theadditionalcost of the line driver,receiver,and interconnectionoverthe cost of OperationModesof operationreferto the directionof dataflow and affectthe electricalrequirementsfor line driversand displaysthe simplexmodefor the unidirectional(nonreversible)

7 Flow of datafromasingleline driverto a singleline SimplexBusThe full-duplexmodeconsistsof two simplexcircuitstransmittingsimultaneousl yin distributedsimplexmodeor differentialmultidropmodeis a singleline drivertransmittingunidirectionalto morethanone March2000 RevisedAugust2017 SubmitDocumentationFeedbackCopyright 2000 2017,TexasInstrumentsIncorporatedCompari ngBus SolutionsFigure4. MultidropBusThe half-duplexmodeis a nonsimultaneous,two-waydataflow betweentwo line driverand receiverpairsor Half-DuplexBusThe logicalextensionof the half-duplexmodeis the multipointbus. A multipointbus is thenonsimultaneous,two-waydataflow amongthreeor moretransceiversconnectedto the samephysicaltransmissionline, as illustratedin Figure6.

8 Multipointline driversand receivershavestringentelectricalrequirem entsand supportall of the othermodesof SerialTransmissionFigure7 illustratesthe differencebetweenparalleland at the sametime overa signalline for eachdatabit. Serialdatabusestransmitonebit afteranotherthrougha singleline by serializing,thende-serializingbackto a higherrate to achievethe samesignalingratesas a parallelbus, bothmethodshaveadvantagesand DataSerial DataParallel DataParallel March2000 RevisedAugust2017 SubmitDocumentationFeedbackCopyright 2000 2017,TexasInstrumentsIncorporatedCompari ngBus SolutionsFigure7.

9 Principleof Paralleland SerialTransmissionLatencyis typicallyreferredto as the time froma datarequestto its ,latencyis lowerinparallelbusesbecausethe time to serializeand deserializethe datais not oftenimplementedfor a parallelbus interfaceby dedicatingspecificbits for the controlofdatatransfer, interconnectioncost advantageof the serialbus is fromthe singledatapaththat resultsin less boardarea,fewerconnectorpins,and less signalingrate advantagegoesto the parallelbus becausethe widthof a bus has no ,distancequicklybecomea criticalfactoras parallelfieldsinteractwith ,shielded,twisted-pair,parallelcablehelp sto slightlyextendthe parallelbus length,but not to the extremelengthsthat can be attainedon a usedto describethe signalingrate or speedof datatransfer,and the designerneedstounderstandthe contextwhenusingsignalingrate minimumunit-intervalor tUIdescribestheminimumtime durationof a singlepulseof a bit signalrise and fall timesor eye-patternjitter as a percentageof the tUI.

10 The inverseof the tUIisthe signalingrate in unitsof bits per secondsuchas kilobitsper second(kbps)or megabitsper second(Mbps).Theseparametersoftendefinet he basicbandwidthrequirementsof a datatransmissioncircuitregardlessof its form,mode,or the inputclockfrequencyin Hertzto describea iscommonlyusedwhencomparingserializerand deserializerproductswith a knownparallelbus Hertzto bits per secondis that a singlebit is typicallyconsideredto be a 180 degreeunit a360 degreecycleis two bits. Therefore,1 Hz is equalto 2 bits per primaryreasonfor standardizinga datainterfaceis the economyof high numberofmanufacturersof standardizedinterchangeableproductssucha s RS-485transceivers,typicallylowerstheend cost to a this purpose,governmentsand Instituteof Electricaland ElectronicEngineers(IEEE),theTelecommuni cationsIndustryAssociation(TIA),and the InternationalStandardsOrganization(ISO)