Self Study Programme 286 - VolksPage.Net

LIN busIntroductionLIN stands for Local Interconnect Network.Local Interconnect means that all control unitsare located within a limited structural space(e.g. roof). This is also referred to as "localsub-system".Data are exchanged between the individualLIN bus systems in a vehicle by one controlunit in each case using the CAN data bus.The LIN bus system is a single-wire bus. Thewire has a basic colour (violet) and a codecolour. The wire cross-section is 0.35 mm 2 .A screen is not necessary.LOCAL INTERCONNECT NETWORKThe system permits data exchange betweenone LIN master control unit and up to 16 LINslave control units.air conditionerLIN master 1Air conditioner control unit LIN slave 1Heated windscreenLIN slave 3PTC additionalheater (right)LIN slave 2Fresh-air blowerLIN slave 4PTC additionalheater (left)LIN master 2Front roof moduleroof moduleLIN slave 1Sun roof motorSSP286_0146

LIN master control unitThe control unit connected to the CAN databus implements the LIN master functions.Functions– Monitoring of data transfer and datatransfer rate.The LIN master control unit transmits theheader (refer to Page 12).– The software contains a cycle specifyingwhen and how often which message istransmitted to the LIN data bus.– Implementation of translation functionbetween the LIN control units of the localLIN bus system and the CAN data bus. It isthus the only control unit in the LIN bussystem which is connected to the CANdata bus.– Diagnosis for the connected LIN slavecontrol units takes place via the LINmaster control unit.Diagnosis interfacefor data bus (gateway)LIN masterLIN slave 1Diagnosis CANSSP286_017Diagnostic connectionLIN slave 27

LIN busLIN slave control unitsLIN slaveSensorsLIN mastert°MActuatorsSSP286_070Individual control units, such as the fresh-airblower, or sensors and actuators, for instancetilt sensor or anti-theft alarm sounder, can beused as LIN slave control units within a LINdata bus system.Integrated sensor electronics evaluate themeasured values.The values are then transmitted as a digitalsignal by the LIN bus.Only one pin of the LIN master socket isrequired for several sensors and actuators.The LIN actuators are intelligent electronic orelectromechanical assemblies which areinformed of their tasks by the LIN mastercontrol unit in the form of the LIN data signal.The LIN master can interrogate the actualstatus of the actuators by way of integratedsensors, thus permitting desired/actualcomparison.The sensors and actuators only react if theLIN master control unit transmits a header.8

Data transferThe data transfer rate is 1 - 20 kbit/s and isspecified in the software of the LIN controlunits. This corresponds to a maximum of onefifth of the data transfer rate of theconvenience CAN.max.20 kbit/sSSP286_061SignalRecessive levelIf no message or a recessive bit is beingtransmitted on the LIN data bus, the voltageat the data bus wire is roughly equivalent tobattery voltage.2V/Div.=Recessive level0,5ms/Div.Dominant levelFor transfer of a dominant bit on the LIN databus, the data bus wire is connected to earthby a transceiver in the transmitter controlunit.TDifferences may be seen between thedominant levels on account of differenttransceiver designs in the control units.Dominant levelSSP286_0719

LIN busReliabilityStable data transfer is guaranteed byspecified transmission and receptiontolerances with regard to both the recessiveand dominant levels.U bat.Transmission voltage range2V/Div.=0,5msU recessive min.80 %U dominant max.20 %Terminal 31SSP286_016TIn order to obtain reception of valid signals inspite of interference, the permissible voltageranges on the reception end are larger.U bat.ms/Div.Reception voltage rangeU recessive min.60 %U dominant max.40 %Terminal 3110TSSP286_022

MessagesHeader(refer to Page 12)Transmitter: LIN masterResponse(refer to Page 13)Transmitter: LIN master or LIN slave2V/Div.=0,5ms/Div.TSSP286_072Message with slave responseIn the header, the LIN master control unitrequests a LIN slave control unit to transmitinformation (e.g. switch statuses or measuredvalues).The response is transmitted by the LIN slavecontrol unit.Message with master commandBy way of the identifier in the header, theLIN master control unit requests thecorresponding LIN slave control units toprocess the data contained in the response.The response is transmitted by the LIN mastercontrol unit.11

LIN busHeaderSynch delimiterIdentifier fieldSynch breakSynch field2V/Div.=0,2ms/Div.TSSP286_073The header is transmitted cyclically by theLIN master control unit.It can be divided into four sections:– Synch break– Synch delimiter– Synch field– Identifier fieldThe synch break has a length of at least 13 bitperiods and is transmitted with dominantlevel.The 13 bit period is necessary tounequivocally indicate the start of a messageto all LIN slave control units.A maximum of 9 dominant bits areconsecutively transmitted in the othermessage sections.The synch delimiter has a length of at least1 bit and is recessive (≈ U bat. ).The synch field consists of the bit sequence0 1 0 1 0 1 0 1 0 1. This bit sequence enablesall LIN slave control units to adapt to (becomesynchronised with) the system clock of theLIN master control unit.The synchronisation of all control units isessential to proper data exchange. Withoutsynchronisation, the bit values would beinserted at an incorrect location in themessage at the receiver.Data transfer errors would result.The identifier field has a length of 8 bitperiods. The first 6 bits contain theidentification and the number of data fields(refer to Page 14) of the response.The number of data fields in the response canbe between 0 and 8.The last two bits contain the checksum of thefirst 6 bits for detection of transmissionerrors. The checksum is required to preventassignment to an incorrect message in theevent of identifier transmission errors.12

ResponseIn the case of a message with slave response,a LIN slave control unit supplies the responsewith information on the basis of the identifier.Example:LIN masterOperating and display unitfor air conditionerLIN slave 1:Heated windscreenSSP286_026Interrogation ofblower speed LIN slave 2:Speed = 150 rpmFresh-air blowersignals actual speedIn the case of a message with a data requestfrom the master, the LIN master control unitsupplies the response.In line with the identifier, the correspondingLIN slave control units process the data forimplementation of functions.Example:LIN masterOperating and display unitfor air conditionerLIN slave 1:Heated windscreenSSP286_062Setblower speedSpeed = 200 rpmLIN slave 2:Fresh-air blowerincreases speedto 200 rpm13

LIN busThe response consists of 1 to 8 data fields.One data field is made up of 10 bits. Eachdata field comprises a dominant start bit, adata byte (containing the information) and arecessive stop bit. The start and stop bit areused for post-synchronisation and thus toavoid transmission error.2V/Div.=0,5ms/Div.SSP286_074TSequence of messagesThe LIN master control unit transmits theheaders and, in the case of master messages,the responses, cyclically to the LIN bus inaccordance with a sequence specified in itssoftware.Frequently required information istransmitted several times.Statuses affecting the LIN master control unitmay alter the message sequence.ResponseIn order to reduce the number of LIN mastercontrol unit component options, the mastercontrol unit transmits the headers for thecontrol units of a fully equipped vehicle to theLIN bus.Control units for special equipment not fittedresult in headers with no responses on theoscillogram.This has no effect on system operation.Examples:– Ignition ON/OFF– Diagnosis active/inactive– Side lights ON/OFFMaster messageRecessive2V/Div.=2ms/Div.DominantTSSP286_07514Header with noresponseSlave message(characterised bydifferent dominant levels)

Anti-theft systemDoor lockNotebookManipulationControl unit 2for vehicleelectrical systemDoor control unitNotebook dataare not understoodControl unit forgarage door openerSSP286_065Data are only transferred in the LIN bussystem if the LIN master control unittransmits a header with the appropriateidentifier.The full monitoring of all messages by the LINmaster control unit makes it impossible tomanipulate any LIN wire on the outside of thevehicle. The LIN slave control unit can onlyrespond.Thus, for example, the doors cannot beunlocked by way of the LIN bus.This arrangement makes it possible to installLIN slave control units (e.g. garage dooropener control unit in front bumper) on theoutside of the vehicle.15

LIN busDiagnosisLIN bus system diagnosis is performed byway of the LIN master control unit addressword.All self-diagnosis functions can beimplemented for the LIN slave control units.The diagnostic data are transferred fromLIN slave control units to the LIN mastercontrol unit by the LIN bus.Fault location Fault message Cause of fault entryNo data transfer byLIN slave control unit over aperiod stipulated inLIN master softwareLIN slave control unite.g. blower controlNo signal/no communication- Open circuit in wiring or short circuit- Fault in power supply of LIN slavecontrol unit- Incorrect LIN slave or LIN mastercomponent option- Fault in LIN slave control unitLIN slave control unite.g. blower controlImplausible signalChecksum errorIncomplete messagetransmission- Electromagnetic interference onLIN wire- Change in capacitance andresistance on LIN wire (e.g. moisture/dirt at connector housing)- Software problem(incorrect component options)16

MOST busIntroductionIn addition to the familiar CAN bus systems,use has been made for the first time in theAudi A8 ´03 of an optical data bus system.The name of this data bus system is derivedfrom "Media Oriented Systems Transport(MOST) Cooperation". This is an associationformed by various motor vehiclemanufacturers, their suppliers and softwarecompanies with a view to developing astandard high-speed data transfer system.Media Oriented Systems TransportThe term "Media Oriented Systems Transport"signifies a network featuring media-orienteddata transport. This means that, in contrast tothe CAN data bus, address-oriented messagesare transmitted to a specific receiver.This technique is used in Audi vehicles for thetransfer of infotainment system data.RThe infotainment system offers a wide rangeof modern information and entertainmentmedia as outlined below.DVD - VideoDAB - Digital radioTelephoneTelematicsCentral displayand controlTV receptionCD/DVD navigationInternetEmailMinidisc/CD audioSSP286_00817

MOST busTransfer rates of media5.94 Mbit/s2.2 Mbit/s0.43 Mbit/s4.4 Mbit/s4.4 Mbit/s1.54 Mbit/s1.54 Mbit/s1.54 Mbit/sSSP286_010NavigationTelephone (GSM)Video (MPEG)Video, reduced (MPEG)Audio source 1 (stereo)e.g. via rear right headphonesAudio source 2 (stereo)e.g. via rear left headphonesAudio source 3 (surround sound)e.g. via digital sound systemNot usedOptical data transfer is an appropriate meansof implementing a complex infotainmentsystem as the CAN data bus systems used todate cannot transmit data quickly enough andthus not in the volume required.The video and audio applications result intransfer rates of many Mbit/s.A transfer rate of roughly 6 Mbit/s is requiredjust to transmit a digital TV signal with stereosound.The MOST bus permits transfer ratesof 21.2 Mbit/s.18

TV tunerIn the past such information (e.g. video andaudio) could only be transmitted in the form ofan analog signal, increasing the scope ofharness wiring required.AudioCANCAN bus systems have a maximum datatransfer rate of 1 Mbit/s. Consequently, it wasonly possible to use CAN bus systems totransmit the control signals.VideoSSP286_002The optical MOST bus enables data to beexchanged between the componentsconcerned in digital form.In addition to fewer wires and less weight,light wave transmission provides a far higherdata transfer rate.In comparison to radio waves, light waveshave very short wavelengths. In addition, theyneither generate nor are susceptible toelectromagnetic interference waves.These factors permit a high data transfer rateand a high level of interference immunity.TV tunerSound systemOperating unitDisplaySSP286_00319

MOST busDesign of control unitsOptical fibreOpticalconnectorInternalpower supplyElectricalconnectorDiagnosisUnit-specificcomponentsLEDPhotodiodeMOST transceiverStandard microcontrollerTransmitter and receiver – Fibre Optical Transmitter (FOT)SSP286_011Components of control units in MOST bus– Optical fibre - optical connectorBy way of this connector, the light signalspass into the control unit or the lightsignals generated are conveyed to the nextbus user.– Electrical connector– Internal power supplyThe supply voltage fed into the control unitby the electrical connector is distributed tothe components by the internal powersupply system. This enables individualcomponents in the control unit to bedeactivated to reduce closed circuitcurrent.This connector is responsible for thepower supply, ring fault diagnosis (refer toPage 41 onwards) and input and outputsignals.20

– Transmitter and receiver – Fibre OpticalTransmitter (FOT)This consists of a photodiode and a lightemittingdiode.Incoming light signals are converted by thephotodiode into a voltage signal which isrelayed to the MOST transceiver. Thefunction of the light-emitting diode is toconvert MOST transceiver voltage signalsinto light signals.The light waves generated have awavelength of 650 nm and are visible as redlight.The data are transmitted by means of lightwave modulation.400 nmSSP286_063650 nmUltravioletInfraredThis modulated light is then conductedthrough the optical fibre to the next controlunit.SSP286_004– MOST transceiverThe MOST transceiver consists of twocomponents, namely the transmitter andreceiver.The transmitter conveys the messages tobe transmitted to the FOT in the form of avoltage signal.The receiver accepts the voltage signalsfrom the FOT and conveys the required datato the standard microcontroller (CPU) of thecontrol unit.Non-required messages from other controlunits pass through the transceiver withoutdata being conveyed to the CPU. Themessages are transmitted in unalteredform to the next control unit.– Standard microcontroller (CPU)The standard microcontroller (CPU) is thecentral processing unit of the control unit.It contains a microprocessor whichcontrols all the major functions of thecontrol unit.– Unit-specific componentsThese components are responsible for theimplementation of functions specific tothe control unit, e.g. CD drive, radio tuner.21

MOST busPhotodiodeThis is designed to convert the light wavesinto voltage signals.p-layerIncident lightContact ring(anode)DesignThe photodiode has a p-n junction, ontowhich light can be focused. On account of aheavily doped p-layer, the depletion layerextends almost exclusively into the n-layer.Depletion layer(p-n junction)There is a contact (anode) at the p-layer.The n-layer is applied to the metallic base(cathode).n-layerFunctionMetal plate(cathode)Electrons0 VSSP286_048The energy associated with the penetration oflight or infrared rays into the p-n junctionresults in the formation of free electrons andholes. These give rise to a flow of currentacross the p-n junction.Consequently, the more light which strikesthe photodiode the higher will be the currentflowing through it.In reverse direction, the photodiode isconnected in series with a resistor.An increase in the current flowing throughthe photodiode on account of more lightstriking it increases the drop in voltage at theresistor. The light signal has thus beenconverted to a voltage signal.This process is referred to as the internalphotoelectric effect.Low incident lightHigh incident light0 A0 AR0 VR0 VSSP286_005SSP286_00622

Optical fibreThe optical fibre is designed to convey thelight waves generated in the transmitter ofone control unit to the receiver of anothercontrol unit.Development of the optical fibre was basedon the following criteria:– Light waves travel in straight lines andcannot be bent. However, they have to berouted through bends in the optical fibre.– The distance between transmitter andreceiver may be several metres –Attenuation (refer to Page 27).– The optical fibre must not be susceptibleto damage caused by mechanical impact(vibration, assembly work).– The optical fibre must operate reliablydespite the great temperature fluctuationsin the vehicle.Requirements to be met by optical fibres usedfor transmitting light signals:– The optical fibre must conduct the lightwaves with a low level of attenuation.– The light waves have to be routed throughbends in the optical fibre.– The optical fibre must be flexible.– The optical fibre must operate reliably inthe temperature range between - 40 °C and85 °C.ReceiverReceivere.g. amplifierKTransmitterTransceiverTransmittere.g. telematics control unitSSP286_02023

MOST busDesign of optical fibreThe optical fibre consists of several layers.The core forms the central part of an opticalfibre. It is made of polymethyl methacrylateand represents the actual light conductor,through which the light passes with virtuallyno losses by way of the total reflectionprinciple. This principle is explained in greaterdetail in the following.The optically transparent fluoropolymercladding around the core is required for totalreflection.The black polyamide cladding protects thecore against external incident light.Coloured claddingBlack claddingThe coloured cladding is used foridentification, protection against mechanicaldamage and thermal protection.ReflectivecladdingCoreSSP286_030dia. 1.0dia. 0.98dia. 1.5SSP286_031dia. 2.324

Transmission of light waves in optical fibreStraight optical fibreTotal reflectionThe optical fibre conducts some of the lightwaves in a straight line through the core.Most of the light waves are conveyed in azigzag pattern as a result of the totalreflection occurring at the core surface.Curved optical fibreThe total reflection occurring at the corecladding boundary causes the light waves tobe reflected and thus conducted through thebend.SSP286_032Total reflectionRadius > 25 mmIf a beam of light strikes a boundary layerbetween materials with higher and lowerrefractive indices at a shallow angle, thebeam is fully reflected, i.e. total reflectiontakes place.In an optical fibre, the material of the core hasa higher refractive index than that of thecladding, with the result that total reflectiontakes place within the core.This effect is governed by the angle of thelight waves striking the boundary from inside.If this angle becomes too steep, the lightwaves will leave the core and high losses willoccur.This situation is encountered if the opticalfibre is excessively bent or kinked.SSP286_033Radius < 25 mmThe bending radius of the optical fibremust not be less than 25 mm.SSP286_03425

MOST busConnectorOptical contact surfacesSignal direction arrowConnector housingOptical fibreFerrulesLockingmechanismPlug connectionSSP286_035Use is made of special optical connectors tolink the optical fibres to the control units.A signal direction arrow on the plugconnection indicates the input (to thereceiver).The connector housing creates the link withthe control unit.The light is transmitted by the end face of thecore to the transmitter/receiver in the controlunit.At the optical fibre production stage, laserweldedplastic ferrules or crimp-type brassferrules are fitted to secure the optical fibre inposition in the connector housing.Optical end faceTo minimise transmission losses, the end faceof the optical fibre must be– smooth– perpendicular and– clean.This can only be achieved using a specialcutting tool.Dirt and scratches on the cut face causehigher losses (attenuation).SSP286_08126

Attenuation in optical busAssessment of the optical fibre conditioninvolves measuring the attenuation.A reduction in the power of the light wavesduring transmission is referred to asattenuation.Attenuation (A) is given in decibels (dB).A decibel is not an absolute quantity, but ratherrepresents a ratio of two values.This also explains why the decibel is not definedfor specific physical quantities.The decibel is also used, for example as a unitfor expressing sound pressure or volume.For attenuation measurement, this quantity iscalculated from the logarithm of the ratio oftransmission power to reception power.Formula:Attenuation ratio (A) = 10 * lgTransmission powerReception powerPlug connection, e.g. 0.5 dBOptical fibre, e.g. 0.6 dBPlug connection, e.g. 0.3 dBExample:20 W10 * lg = 3 dB10 WThis means that the light signal is reduced byhalf for an optical fibre with an attenuation ratioof 3 dB.In other words, the higher the attenuation ratio,the poorer the signal transmission.SSP286_045Totalattenuation ratio = 1.4 dB(in this example)If several components are involved in thetransmission of light signals, the attenuationratios of the components can be added up toform a total attenuation ratio in the same way asthe resistances of electrical componentsconnected in series.As in the MOST bus each control unitre-transmits the light waves, only the totalattenuation ratio between two controlunits is of significance.27

MOST busCauses of increased attenuation in the opticaldata bus1. Optical fibre bending radius too smallBending the optical fibre to a radius ofless than 5 mm (kinking) obscures thecore (comparable with bent perspex) atthe bending point.The optical fibre has to be replaced.2. Damage to optical fibre cladding.3. End face scratched.4. End face dirty.5. End faces offset(connector housing broken).6. End faces not in line(angle error).7. Gap between end face of optical fibreand contact surface of control unit(connector housing broken or notengaged).8. Ferrule not properly crimped.SSP286_06928

Optical fibre anti-kink sleeveFitting an anti-kink sleeve guarantees aminimum optical fibre radius of 25 mm.SSP286_087Rules for handling optical fibres and theircomponents– Never employ thermal working and repairmethods such as soldering, hot bondingor welding– Never employ chemical and mechanicalmethods such as bonding and jointing– Never twist together two optical fibrecables or an optical fibre cable and acopper wire– Avoid contaminating end face, e.g. withfluids, dust or other media; prescribedprotective caps are only to be removed forconnection or test purposes employingextreme care– Avoid loops and knots when laying invehicle; pay attention to correct lengthwhen replacing optical fibre– Avoid cladding damage such asperforation, cutting or crushing: Do notstand or place objects on cladding, etc.when fitting in vehicle29

MOST busRing configuration of MOST busCD changerTelematicsControl unit for frontinformation displayand operating unitDisplayTV tunerOperating unitDiagnosis interfacefor data bus J533(gateway)RadiotunerMap readerVoicecontrolNavigationAmplifierSSP286_047DiagnosticconnectionA distinguishing feature of the MOST bussystem is its ring configuration.The control units transmit data in onedirection via an optical fibre to the nextcontrol unit in the ring.This completes the ring.MOST bus system diagnosis is implementedby way of the data bus diagnosis interfaceand the diagnosis CAN.This process continues until the data returnto the control unit which originallytransmitted them.30

System managerTogether with the diagnosis manager, thesystem manager is responsible for systemadministration in the MOST bus.The diagnosis interface for data bus J533(gateway) assumes the diagnosis managerfunctions in the Audi A8 ´03 (refer to Page 41).Functions of system manager:– Control of system statuses– Transmission of MOST bus messages– Management of transmission capacitiesThe control unit for front information displayand operating unit J523 implements thesystem manager functions.MOST bussystem statusesSleep modeThere is no data exchange in the MOST bus.The units are switched to standby and canonly be activated by an optical start pulsefrom the system manager.The closed-circuit current is reduced to aminimum.Sleep mode activation conditions:– All control units in MOST bussystem indicate readiness to switchto sleep mode.– No requests from other bussystems via the gateway.– Diagnosis not active.At a higher ranking level, the MOST bussystem can be switched to sleep modeSSP286_066– by the battery manager via the gateway inthe event of starter battery discharge– by activation of transport mode via thediagnosis tester31

MOST busStandby modeNo functions are available to the user, i.e. thesystem gives the impression of being switchedoff. The MOST bus system is active in thebackground, however all output media (display,radio amplifier etc.) are either inactive ormuted.This mode is active on starting andduring system run-on.Activation of standby mode– Activation by other data busesvia gateway, e.g. unlocking/opening of driver's door, ignition ON– Activation by control unit in MOST bus,e.g. incoming call (telephone)SSP286_067Power ONThe control units are fully activated. Data areexchanged on the MOST bus. All functions areavailable to the user.Prerequisites for Power ON mode:– MOST bus system in standby mode– Activation by other data buses viagateway e.g. S-contact,display active– Activation by user functionselection, e.g. via multimediaoperating unit E380Further information on system statusactivation can be found in the SelfStudy Programmes for the appropriatevehicle models.SSP286_06832

FramesThe system manager transmits the frames tothe next control unit in the ring at a clockfrequency of 44.1 kHz.Clock frequencyOn account of the fixed time slot pattern, theclock frequency permits the transmission ofsynchronous data.The magnitude of a frame is 64 bytes,divided up as indicated below.Synchronous data are used to carryinformation such as sound and movingimages (video) which always has to betransmitted at the same intervals.The fixed clock frequency of 44.1 kHzcorresponds to the transmission frequency ofdigital audio units (CD, DVD player, DAB radio)and thus permits the connection of theseunits to the MOST bus.Structure of a frameData field(480 bits)Status field(7 bits) Parity field(1 bit)SSP286_036SSP286_037Preamble(4 bits)Delimiter(4 bits)1st check byte(8 bits)2nd check byte(8 bits)1 byte corresponds to 8 bits.33

MOST busFrame areasThe preamble marks the start of a frame.Each frame in a block has a separatepreamble.SSP286_039A delimiter creates a clear distinctionbetween the preamble and the subsequentdata fields.SSP286_040The data field is used by the MOST bus totransmit up to 60 bytes of user data to thecontrol units.A distinction is made between two types ofdata:– Audio and video in the form ofsynchronous data– Images, information for calculationpurposes and messages in the form ofasynchronous dataThe asynchronous data are entered and thustransmitted to the receiver in packets of4 bytes (quadlets) on the basis of thetransmitter/receiver addresses (identifier) andthe available asynchronous volume.The corresponding data transfer processesare described in more detail on Page 38onwards.The data field has a flexible structure. Theproportion of synchronous data in the datafield is between 24 and 60 bytes. Thetransmission of synchronous data haspriority.Asynchronous data0 - 36 bytesSSP286_041Synchronous data24 - 60 bytes34

The two check bytes are used to transmitinformation such as– Transmitter and receiver address(identifier)– Control commands to receiver(e.g. amplifier setting up/down)SSP286_042The block check bytes are assembled in thecontrol units to form a check frame. One blockconsists of 16 frames. The check framecontains control and diagnosis data to betransferred from a transmitter to a receiver.This is referred to as address-oriented datatransfer.Example:Transmitter – Control unit for frontinformation display andoperating unitReceiver – AmplifierControl signal – up/downCheck bytes/frame 2Check bytes/frame 1SSP286_038The status field of a frame contains frametransmission information for thereceiver.SSP286_043The parity field is used for a final check thatthe frame is complete. The content of thisfield governs whether a transmission processis repeated.SSP286_04435

MOST busOperating sequences inMOST busRemote controlControl unit forcentral lockingsystemDiagnosis interfacefor data bus(gateway)LED is switched toslave lightRecognition of light signal –Initiation of system startSystem managerSSP286_046System start (wake-up)If the MOST bus is in sleep mode, the wakeupprocess initially switches the system tostandby mode.If one of the control units, with the exceptionof the system manager, wakes the MOST bus,it transmits specially modulated light – slavelight – to the next control unit.By way of the photodiode which is active insleep mode, the next control unit in the ringreceives the slave light and passes it on.This process continues right through to thesystem manager. In the incoming slave lightthe manager recognises the prompt forsystem starting.The system manager then transmits anotherspecially modulated light – master light – tothe next control unit. This master light isrelayed by all control units. Reception of themaster light in its FOT informs the systemmanager that the ring is complete and frametransmission commences.36

FOT recognisesclosed ringSSP286_076LED is switched tomaster lightSystem managerIn the first frames the control units in theMOST bus are requested to provideidentification.Based on the identification, the systemmanager transmits the current sequence(actual configuration) to all control units inthe ring. This permits address-oriented datatransfer.The diagnosis manager compares thereported control units (actual configuration)to a stored list of control units fitted(specified configuration).If the actual and specified configurations donot coincide, the diagnosis manager storescorresponding fault memory entries.This completes the wake-up process and datatransfer can commence.SSP286_086FramesSystem managertransmits frames37

MOST busAudio and video transmission in the form ofsynchronous dataFunctionselectionMultimediaoperating unit E380System managerControl unit for front informationdisplay and operating unit J523Frame toCD driveFrame withcheck data fromdigital sound package controlunit J525Frame todigital sound packagecontrol unit J525CD drive(data source)SSP286_077Digital sound packagecontrol unit J525(data receiver)Frame with check datafrom CD driveBy way of explanation, synchronous datatransfer is described on the basis of the modeof operation involved in playing a music CD inthe Audi A8 '03.With the aid of the multimedia operating unitE380 and the information display unit J685,the user selects the desired track on themusic CD.By way of a data wire, the operating unit E380transmits the control signals to the controlunit for front information display andoperating unit J523 (system manager).Corresponding information can be found inthe Self Study Programme 293 – Audi A8 ´03Infotainment.The system manager then inserts a messageblock (= 16 frames) with the check data intothe frames constantly transmitted.– Transmitter address:- Control unit for front information displayand operating unit J523, position 1 in ring– Receiver address of data source:- CD drive,position in ring (depends on equipment)– Control commands:- Play track 10- Assign transmission channelsThe CD drive (data source) determines whichbytes in the data field are available fortransmitting its data.It then inserts a block with the check data.– Transmitter address of data source:- CD drive,position in ring (depends on equipment)– Receiver address of system manager:- Control unit for front information displayand operating unit J523, position 1 in ring– Control command:- Data transfer/music CD on channels01, 02, 03, 04 (stereo))38

Data managementwith synchronous transmissionChannel for voice output(e.g. mono)Channel for CD changer(e.g. stereo)Channel for DVD player(e.g. surround)Free bytes withindata fieldNavigation control unit CD changer DVD playerSSP286_078The control unit for front information displayand operating unit J523 then uses a block withthe check data– Transmitter address:- Control unit for front information displayand operating unit J523, position 1 in ring– Receiver address:- Digital sound package control unit J525,position in ring (depends on equipment)– Control commands:- Read out data channels 01, 02, 03, 04 andreproduce via speakers- Current sound settings such as volume,fader, balance, bass, treble, middle- Deactivate mutingto issue the instruction to the digital soundpackage control unit J525 (data receiver) toreproduce the music.The music CD data are retained in the datafield until the frame reaches the CD drive(i.e. the data source) again via the ring.The data are then replaced by fresh data andthe cycle commences again.This permits use of the synchronous data byall output units (sound package, headphoneconnections) in the MOST bus.The system manager determines which unit isto use the data by transmitting thecorresponding check data.Transmission channelsAudio and video transmission requires severalbytes in each data field. The data sourcereserves a number of bytes in line with thetype of signal. The bytes reserved are referredto as channels. One channel contains one byteof data.Number of transmission channelsSignal Channels/bytesMono 2Stereo 4Surround 12This reservation of channels permits thesimultaneous transmission of synchronousdata from several data sources.39

MOST busTransmission of data for images, messagesand functions in the form of asynchronousdataFrame with data fromnavigation control unitMonitor(data receiver)Check datafrom monitorNavigation control unitwith latch (data source)Telephone control unitwith latch (data source)Map displayfrom CD/DVDInternet sitesEmailFrame with data fromtelephone control unitSSP286_079The data for– Navigation system map display– Navigation calculations– Internet sites– Emailare transmitted in the form of asynchronousdata.The asynchronous data sources transmit atirregular intervals.For this purpose, each source stores itsasynchronous data in a latch.The data source then waits until it receives amessage block with the address of thereceiver.The source enters the data into the free bytesin the data fields of this message block.This takes place in packets (quadlets) of4 bytes each.The receiver reads the data packets in thedata fields and processes the information.The asynchronous data are retained in thedata fields until the message block returns tothe data source.The data source extracts the data from thedata fields and replaces them with fresh dataif applicable.40

DiagnosisDiagnosis managerIn addition to the system manager, the MOSTbus also has a diagnosis manager.This is responsible for ring fault diagnosisand transmits the diagnosis data of thecontrol units in the MOST bus to thediagnosis unit.In the Audi A8 ´03, the diagnosis interface fordata bus J533 implements the diagnosticfunctions.SSP286_057System malfunctionOn account of the ring configuration,interruption of data transfer at a given MOSTbus location is referred to as a ring break.Possible causes of break in ring:– Break in optical fibre– Fault in power supply of transmitter orreceiver control unit– Defective transmitter or receiver controlunitRing fault diagnosis must be performed tolocalise a break in the ring.Ring fault diagnosis is part of the final controldiagnosis routine of the diagnosis manager.Consequences of break in ring:– No audio and video reproduction– No control and adjustment by way ofmultimedia operating unit– Entry in diagnosis manager fault memory("Break in optical data bus")Ring fault diagnosisRing fault diagnosis wireAs a break in the ring prevents data transferin the MOST bus, ring fault diagnosis isimplemented with the aid of a diagnosis wire.The diagnosis wire is linked by way of acentral wiring connection to each MOST buscontrol unit.41

MOST busDiagnosis wireDiagnosticconnectionSSP286_080Break in optical fibreAfter starting ring fault diagnosis, thediagnosis manager transmits a pulse via thediagnosis wire to the control units.This pulse causes all control units to transmitlight signals with the aid of their transmissionunit in the FOT.In this process, all control units check– their power supply and internal electricalfunctions.– Reception of light signals from precedingcontrol unit in ring.Each MOST bus control unit respondsfollowing a time period stipulated in itssoftware.The time period between start of ring faultdiagnosis and control unit response enablesthe diagnosis manager to recognise whichcontrol unit has transmitted the response.Content of responseFollowing start of ring fault diagnosis, the MOSTbus control units transmit two items ofinformation:1. Control unit in proper electrical working order– i.e. electrical functions of control unit(e.g. power supply) are OK2. Control unit in proper optical working order– its photodiode receives the light signal fromthe preceding control unit in the ringThese messages inform the diagnosis manager– of any electrical faults in the system (fault inpower supply)– or of the control units between which there isa break in optical data transfer.42

Ring fault diagnosis with increased attenuationIncreasedattenuation,e.g. constrictedoptical fibreSSP286_088Ring fault diagnosis only permits detectionof a break in data transfer.The final control diagnosis function of thediagnosis manager additionally contains ringfault diagnosis with reduced light power fordetection of increased attenuation.The ring fault diagnosis process with reducedpower corresponds to that described above.However, the control units switch on theirLEDs in the FOT with an attenuation of 3 dB,i.e. with light power reduced by half.If the optical fibre is subject to increasedattenuation, the light signal reaching thereceiver is of insufficient strength. Thereceiver signals "optical problem".The diagnosis manager thus recognises thefault location and issues a correspondingmessage in the assisted fault-finding of thediagnosis tester.43

Bluetooth TMIntroductionMobile phoneCordless telephone handsetin Audi A8 ´03FutureapplicationsNotebookControl unitfor telephoneHolder forcordless telephone handsetSSP286_085Mobile communication and information aregaining in importance in both the modernbusiness world and the private sector.For example, it is not unusual for one personto use several mobile systems such as mobilephone, Personal Digital Assistant (PDA) ornotebook.In the past, the exchange of informationbetween mobile systems required the use of ahard wire or infrared techniques.Such non-standardised links greatly restrictedmobility or were complicated to use.Bluetooth TM technology provides the solutionby creating a standardised radio link forconnecting mobile systems from differentmanufacturers.This technique is to be introduced for the firsttime in the Audi A8 ´03 to provide a wirelesslink between the telephone handset and thecontrol unit for telephone/telematics.44

Additional applications for the vehicle userare planned for the future:– Installation of second handset at rear ofvehicle– Connection of notebooks, smart phonesand notepads to the internet forinformation transmission andentertainment– Reception and transmission of emails viauser's notebook or PDA– Transmission of addresses and telephonenumbers from user's notebook or PDA toMultimedia Interface (MMI) system– Hands-free unit for mobile phones with noadditional cable adapters– Use of Bluetooth TM technology in othervehicle systems(example: remote control forauxiliary heating)What is Bluetooth TM ?The Swedish company Ericsson proposed thedevelopment of a standardised short-rangewireless system – Bluetooth TM technology.Several other companies decided to join inwith this project and today the BluetoothSpecial Interest Group (SIG) includes some2000 companies from the fields oftelecommunications, data processing andequipment and vehicle manufacturing.The name "Bluetooth" originates from theViking king Harald Blåtand, who unifiedDenmark and Norway in the tenth century andwas known by the nickname "Blue tooth".As this system combines a wide range ofdifferent information, data processing andmobile phone systems it reflects thephilosophy of king Harald and thus came to beknown as Bluetooth TM .45

Bluetooth TMOperationDesignShort-range transceivers (transmitters andreceivers) are either installed directly inselected mobile units or integrated by way ofan adapter (e.g. PC card, USB).Communication takes place in the 2.45 GHzfrequency band which is freely availableworldwide.The extremely short wavelength of thisfrequency permits integration of– Aerial– Control and encoding– Entire transmission and reception systeminto the Bluetooth TM module.The compact design of the Bluetooth TMmodule makes it suitable for installation evenin miniature electronic devices.A link is automatically established betweenany two Bluetooth TM units entering intocontact with one another. Before this canoccur, once-only matching of the units has tobe implemented by entering a PIN.Information on the procedure involved can befound in SSP 293 – Audi A8 Infotainment.This involves the creation of miniaturewireless cells known as "Piconet" fororganisational purposes.One piconet provides space for a maximum ofeight active Bluetooth TM units, however eachunit may form part of several picocells at thesame time. In addition, up to 256 non-activeunits can be assigned to one piconet.One unit assumes the master function in eachpiconet:– The master establishes the link.– The other units are synchronised with themaster.– Only the unit receiving a data packet fromthe master can transmit a response.Example:In the Audi A8 ´03, the telephone/telematicscontrol unit is the Bluetooth TM master.SSP286_082The data transfer rate is up to 1 Mbit/s. Theunits can transmit up to three voice channelssimultaneously.Bluetooth TM transmitters have a range of tenmetres. Up to 100 metres can be achievedwith an additional amplifier for specialapplications.To avoid chaos when creating a piconet,settings can be made on each unit todetermine the unit with which it is allowed tocommunicate or not.Each unit has a unique worldwide addresswith a length of 48 bits, thus permittingunequivocal identification of more than281 billion units.Data transfer does not require anycomplicated settings.46

Operation2.480 GHzJamming by otherelectronic devices(e.g. microwave)1 MHz*2.402 GHz{min. 625 µsTime [t]SSP286_083* Transmission range: 79 1 MHz channelsMaster message (request)Slave message (response)Data transfer in the Bluetooth TM systeminvolves the use of radio waves in a frequencyrange between 2.40 and 2.48 GHz.This frequency range is also used for otherapplications.Examples:– Garage door openers– Microwave ovens– Medical appliancesThe control module– Divides the data into short and flexibledata packets with a duration of approx.625 µs.– Uses a 16-bit checksum to check that thedata packets are complete.– Automatically re-transmits data packetssubject to interference.– Makes use of stable language encoding inwhich the language is converted intodigital signals.Interference immunityThrough the use of measures designed toenhance interference immunity, Bluetooth TMtechnology reduces the interference causedby such equipment.The radio modulechanges the transmission and receptionfrequency 1600 times per second on arandom basis after each data packet. This isreferred to as frequency hopping.47

Bluetooth TMData securityDuring the development of Bluetooth TMtechnology, the manufacturers placed greatemphasis on the protection of the datatransmitted against manipulation andunauthorised monitoring.A 128-bit code is used to encode the data.The authenticity of the receiver is alsochecked with a 128-bit code. In this processthe units use a secret password for mutualidentification of the individual users.A new code is generated for each link.As the range is restricted to 10 metres,manipulation can only take place within thisarea, thus additionally enhancing datasecurity.The above-mentioned interference immunitymeasures also increase the level of protectionagainst manipulation of the data stream.Data security can be further increased byequipment manufacturers through theadditional use of complex encoding methods,different security levels and networkprotocols.48

DiagnosisThe diagnostic procedure for the Bluetooth TMlink is implemented with the aid of the mastercontrol unit address word.Example:In the Audi A8 ´03, the telephone/telematicscontrol unit J526 is the Bluetooth TM master.Address word Telephone 77Emergency call module 75The Bluetooth TM link between the telephonehandset and the telephone/telematics controlunit J526 is monitored by checking theBluetooth TM aerial.An entry is made in the fault memory if thereis a break in the link with the aerial.Bluetooth TM aerialThe measured value blocks provide a displayof– The number– The unit number– The field strength of the radio linkof the portable units communicating with themaster control unit.The Bluetooth TM function can be activated ordeactivated in the Bluetooth TM masteradaption process.Examples:– Transportation of vehicle by air– Use of vehicle in countries whereBluetooth TM frequencies are notauthorised– No signal/no communication49

Diagnosis busIntroductionThe diagnosis CAN is used to exchange databetween the diagnosis unit and the controlunits fitted in the vehicle, thus obviating theneed for the K or L-wires previously required(exception: emission-specific control units).Diagnosis is implemented using the vehiclediagnostic, testing and information systemVAS 5051 or the vehicle diagnostic and serviceinformation system VAS 5052.The control-unit diagnostic data aretransmitted by way of the respective data bussystem to the diagnosis interface for data busJ533 (gateway).Dash panel insert CANDrive system CANConvenience CANAdaptive cruise control CANMOSTThanks to the rapid data transfer via the CANand the high performance of the gateway, thediagnosis unit is able to display a list of thecomponents fitted and their fault statusimmediately after connection to the vehicle.Diagnosis CANDiagnosis interfacefor data bus(gateway)SSP286_012The diagnosis CAN uses a non-screenedtwisted pair of wires with a cross-section of0.35 mm 2 each.CAN highThe CAN low wire is orange/brown and theCAN high wire orange/violet.Data are transferred at a rate of 500 kbit/s infull duplex mode. This means that data can betransmitted in both directions at once.CAN lowSSP286_05550

Diagnosis can be implemented under thefollowing conditions:No. Diagnosis Condition Remarks12StartImplementationWith ignition onWith ignition offWith ignition onYesYes, but notin sleep modeYesWake-up ofcontrol unit viadiagnosis CANis notpossibleWith ignition offYes, but nowrite functions(e.g. control unitencoding)3EndTermination by switching offignitionNoImplementation of diagnosis on the vehiclerequires use of the new diagnosis wiresVAS 5051/5A (3 m) or VAS 5051/6A (5 m).These new diagnosis wires can also beused with the familiar diagnosis systemsemploying K or L-wire.SSP286_056The current basic software version is alsorequired for diagnosis.VAS 5051: Basic software 3.0 for diagnosisvia CANVAS 5052: Basic softwareVAS 5052Vehicle diagnostic and service information systemVersion -GB- / V01.02 20/08/2001Vehicleself-diagnosisElsa WinBasic software modification is accompaniedby the addition of new functions andalterations to the tester user interface.PrintHelpApplicationsAdministrationSSP286_05151

Diagnosis busExtension of forms of addressIn addition to the direct addressing ofindividual control units, provision is now alsomade for group addressing, i.e. the faultmemory content of several control units canbe interrogated more or less simultaneously.This considerably speeds up readout of thefault memory content.Selective control element testThe selective control element test permitsdirect activation of actuators without havingto adhere to a specified sequence.Assisted fault-findingFunctional testSelective control element test, -J520 CU 2Vehicle electrical systemTest sequenceAudi V00.03 25/04/2002Audi A8 2003>2003 (3)SaloonBFL 3.7l Motronic / 206 kWIn addition, it is possible to simultaneouslydisplay control-unit measured value blocks forchecking switches and sensors.The control element routine permits selectiveactuation of individual control elements of vehiclevoltage control unit 2 if fitted/encoded.Ready1. FunctionaldescriptionThese new features offer additional options aspart of assisted fault-finding.MeasurementVehicle selfdiagnosisJump Print HelpSSP286_089Assisted fault-findingFunctional testSelective control element test, -J520 CU 2Vehicle electrical systemAudi V00.03 25/04/2002Audi A8 2003>2003 (3)SaloonBFL 3.7l Motronic / 206 kWControl element interrogation 1 to 6Which control element is to be actuated?(control element selection 1 to 6)1. Retract MMI display rotation mechanism2. Extend MMI display rotation mechanism3. KI58D 90% interior light dimming4. Servotronic/full power assistance5. Servotronic/no power assistance6. Extend right headlight washer system nozzle- 1 -- 2 -- 3 -- 4 -- 5 -- 6 -1. Functionaldescription- Return -MeasurementVehicle selfdiagnosisJump Print HelpSSP286_09052

Example:The illustration shows the selective controlelement test for vehicle voltage control unit 2J520 in the Audi A8 ´03 for checking thedisplay mechanism.Assisted fault-findingFunctional testSelective control element test, -J520 CU 2Vehicle electrical systemAudi V00.03 25/04/2002Audi A8 2003>2003 (3)SaloonBFL 3.7l Motronic / 206 kWWith measured values/messagesActive control element: Extend MMI display rotationmechanismMeasured values/messages:1. FunctionaldescriptionMMI limit switch open: Not actuatedMMI limit switch closed: ActuatedMMI motor : InactiveContinue withMeasurement Jump Print HelpSSP286_091Pin assignment at diagnostic connectorPinWire1 Terminal 154 Earth5 Earth6 Diagnosis CAN (high)7 K-wire14 Diagnosis CAN (low)15 L-wire16 Terminal 30Pins not listed are not used at present.SSP286_05253

54Notes

286All rights reserved.Subject to technical modification.Copyright* 2002 AUDI AG, IngolstadtDepartment I/VK-35D-85045 IngolstadtFax 0841/89-36367000.2811.06.20Technical status as at 05/02Printed in Germany