Audi Self Study Program 971303 – New Data Bus Systems SSP 971303 - Audi New Data Bus Systems

New Data Bus
Systems

Self-Study Program
Course Number 971303

Audi of America, Inc.
Service Training
Printed in U.S.A.
Printed 12/2002
Course Number 971303

©2002 Audi of America, Inc.
All rights reserved. All information contained

in this manual is based on the latest
information available at the time of printing and
is subject to the copyright and other intellectual
property rights of Audi of America, Inc., its
affiliated companies and its licensors. All rights
are reserved to make changes at any time
without notice. No part of this document may
be reproduced, stored in a retrieval system,
or transmitted in any form or by any
means, electronic, mechanical, photocopying,
recording or otherwise, nor may these
materials be modified or reposted to other sites
without the prior expressed written permission
of the publisher.

All requests for permission to copy and
redistribute information should be referred to
Audi of America, Inc.

Always check Technical Bulletins and the
Audi Worldwide Repair Information System
for information that may supersede any
information included in this booklet.

Trademarks: All brand names and product
names used in this manual are trade names,
service marks, trademarks, or registered
trademarks; and are the property of their
respective owners.

Table of Contents

Introduction ...............................................................................1

Innovation, Overview

Local Interconnect Network Data Bus ....................................4

Introduction, LIN Master Control Modules, LIN Slave
Control Modules, Data Transmission, Signal, Transmission
Reliability, Messages, Message Header, Message
Contents (Response), Theft Protection, Diagnosis

Fiber-Optic Data Bus...............................................................15

Introduction, Transmission Rates of Media,
Control Module Design, Fiber-Optic Cable, Ring Structure
of the Fiber-Optic Data Bus, System Manager,
MOST Fiber-Optic Data Bus System Conditions,
Message Frames, Function Flow in the MOST Fiber-Optic
Data Bus, Transmission of Sound and Video as
Synchronous Data, Diagnosis

Bluetooth .................................................................................47

Introduction, Design and Function, Diagnosis

Diagnosis CAN Data Bus ........................................................53

Overview

Knowledge Assessment .........................................................57

The Self-Study Program provides you with information
regarding designs and functions.

New !

Important/Note!

The Self-Study Program is not a Repair Manual.

For maintenance and repair work, always refer to the
current technical literature.

i

Innovation

Introduction

The demand for increases in functionality
and comfort in automobiles stimulates an
ever-increasing need for more and better
vehicle electronic systems.

When the first Audi A8 was introduced in
1994, 15 control modules were sufficient to
support all vehicle functions. The number
of control modules used in the new 2003
Audi A8, has increased five-fold.

This increase in the use of electronics
spurred a search for new ways to transmit
data between the individual control
modules in the vehicle.

Number of Control Modules

The Audi introduction of the CAN data bus
in the mid-nineties was a first and
important step. However, the CAN data bus
system strains against the limits of data
transmission rates, especially for
Infotainment applications.

To fill the need for rapid transmission of
increasing amounts of information, data­transmission systems have been
developed to suit the specific needs of the
vehicle systems that they serve. Service
and on-board diagnostics also profit from
these developments.

Extent of Network

SSP286/064

1

Introduction

Overview

Based on the limitations of current
networks, the increasing number of control
modules needed and their divided
functions, and the increasing amount of
data exchange required, further
developments in data transmission
technology must be exploited for use in
automobiles.

The following data exchange innovations
have been added to the familiar CAN data
bus systems already in place for use in
Audi vehicles:

• Single-wire data bus – Local Interconnect
Network (LIN) data bus.

• Fiber-optic data bus – Media-Oriented
Systems Transport (MOST) data bus.

• Wireless data bus – Bluetooth wireless
data transmission technology.

2

Introduction

Drivetrain CAN Data Bus
Instrument Panel / Gateway Interface

CAN Data Bus
Distance Regulation CAN Data Bus

Diagnosis CAN Data Bus

Convenience CAN Data Bus
Local Interconnect Network

(LIN) Data Bus
Fiber-Optic Data Bus (MOST)

SSP286/001

3

Local Interconnect Network Data Bus

Introduction

The acronym “LIN” stands for “Local
Interconnect Network.”

“Local interconnect” means that all control
modules in an individual network are
located within a limited vehicle area, such
as the roof. This kind of network is also
sometimes called a “local sub-system.”

Local Interconnect Network SSP286/013

Climate Control

The data exchange between the individual
LIN systems in a vehicle is always
controlled by a control module through
the CAN data bus.

Each LIN data bus system functions as a
single wire bus. The base color of the wire
insulation is violet with an identifying stripe
in an additional color. The wire gage is

0.35 mm. Shielding is not necessary.
Each LIN data bus system allows data

exchange between a LIN master control
module and up to 16 LIN slave
control modules.

LIN Slave
Control Module 1
Heated Windshield
Control Module J505

LIN Slave
Control Module 3
Right Rear Footwell
Heater Z43

LIN Master

Control Module 1
Climatronic Control
Module J255

Infotainment
CAN Data Bus

LIN Master
Control Module 2
Roof Electronics
Control Module J528

Roof Module

LIN Slave
Control Module 2
Control Module for
Fresh Air Blower J126

LIN Slave
Control Module 1
Motor for Sliding
Sunroof, Rear V146

LIN Slave
Control Module 4
Left Rear Footwell
Heater Z42

SSP286/014

4

Local Interconnect Network Data Bus

LIN Master Control Modules

The control module in the LIN system that
is connected to a CAN data bus performs
the LIN master control module function.

The LIN master control module controls the
data transfer and the data transfer speed. It
also sends the message header.

For more information on
message headers, please
refer to page 10.

Example of LIN Interfaces

Data Bus On-Board
Diagnostic Interface
J533 (Gateway)

The software contains a cycle to control
when and how often a message is sent on
the LIN data bus.

The LIN master control module assumes
the translation function between the LIN
slave control modules of the local LIN data
bus system and the associated CAN data
bus.

The LIN master control module is the only
control module in a LIN data bus system
that is also connected to a CAN data bus.

The connected LIN slave control modules
are diagnosed through the LIN master
control module.

LIN Master
Control Module
Climatronic Control
Module J255

LIN Slave
Control Module 1
Heated Windshield
Control Module J505

16-Pin Connector T16
(Diagnostic Connection)

LIN Slave
Control Module 2
Control Module for
Fresh Air Blower J126

SSP286/017

5

Local Interconnect Network Data Bus

LIN Slave Control Modules

LIN slave control modules can be either
individual control modules like the Control
Module for Fresh Air Blower J126, or
sensors and actuators like a Vehicle
Inclination Sensor G384 or a Signal Horn for
Alarm System H18, and all be components
of a LIN data bus system.

Electronics that evaluate the measured
values are integrated in the sensors.
Communication of these values is then
accomplished on the LIN data bus in the
form of a digital signal.

LIN Slave Control Modules

Sensors

Only one pin is needed for several
sensors and actuators at the socket of the
LIN master control module.

The LIN actuators are intelligent
electro-mechanical subsystems that receive
their commands in form of LIN data signals
from the LIN master control module. The
actual condition of the actuators can be
monitored by the LIN master control
module. This allows comparison between
actual and specified values.

The sensors and actuators
only respond when a header
is sent by the LIN master
control module.

Actuators SSP286/070

LIN Master
Control Module

6

Local Interconnect Network Data Bus

Data Transmission

The data transmission rate can be from
1 to 20 kilobits per second. A specific rate
is programmed into the software of each
LIN control module. This is at most
approximately one-fifth of the data
transmission rate of the convenience
CAN data bus.

Signal

Recessive level

If no message or a recessive bit is sent on
the LIN data bus, the voltage of the data
bus wire is close to battery voltage.

Dominant level

To transmit a dominant bit on the LIN data
bus, the data bus wire is switched to
ground by a transceiver in the transmitter
control module.

Because of different designs
of transceivers in the control
modules, differences in the
dominant levels may be
visible on the display.

1 to 20 Kbit/s

SSP286/061

Recessive Level

2V/Div. = 0,5ms/Div.

T

SSP286/071

Dominant Level

7

Local Interconnect Network Data Bus

Transmission Reliability

Voltage Range for Transmitting

V

battery

V

recessive minimum

80%

By specifying tolerances for transmitting
and receiving within the range of recessive
and dominant levels, a stable data transfer
is assured.

V

dominant maximum

Terminal 31

Voltage Range for Receiving

V

battery

V

recessive minimum 60%

V

dominant maximum

20%

SSP286/016

To be able to receive valid signals in spite of
interference radiation, the specified voltage
ranges are higher on the receiving side.

40%

Terminal 31

8

SSP286/022

Messages

Local Interconnect Network Data Bus

Message with Slave Answer

In the message header, the LIN master
control module requests information such
as switch conditions or measuring values
from a LIN slave control module.

The LIN slave control module sends the
information back to the LIN master control
module in response.

Message Header
(See Page 10)
Transmitter:
LIN Master
Control Module

2V/Div.= 0,5ms/Div.

Message with Master Instructions

Using an identifier in the message header,
the LIN master control module can also
request that the LIN slave control module
process the data contained in its response.

The LIN master control module processes
the data and sends the response.

Message Contents
(Response, see
page 11) Transmitter:
LIN Master or LIN
Slave Control Module

T

SSP286/072

9

Local Interconnect Network Data Bus

Message Header

The LIN master control module transmits
the header in cycles.

The header can be subdivided into
four sections:

• Synchronization break

• Synchronization delimiter

• Synchronization field

• Identifier field

The synchronization break (synch break)
is at least 13 bits long. It is sent with the
dominant level.

The length of 13 bits is necessary to clearly
inform the LIN slave control modules about
the start of a message.

In the succeeding messages, a maximum
of 9 dominant bits are transmitted one after
the other.

The synchronization delimiter
(synch delimiter) is at least 1 bit long and
recessive (~V

battery

).

The synchronization field (synch field)
consists of the bit rate 0 1 0 1 0 1 0 1 0 1.

2V/Div. =

Because of this bit rate, all LIN slave control
modules can adapt to or synchronize with
the system cycle of the LIN master
control module.

The synchronization of all control modules
is necessary for an error-free data
exchange. Loosing the synchronization
would cause the insertion of the bit values
into the message at the receiving end. This
would lead to errors in the data transfer.

The identifier field is 8 bits long. The
first 6 bits contain the message
identification and the number of data fields
of the response (see page 12).
The number of data fields in the response
may be between 0 and 8.

The last 2 bits contain the check-total of the
first 6 bits for the identification of
transmission errors. The check total is
necessary to avoid the assignment of the
identifier to a wrong message in case of a
transmission error.

Synchronization Delimiter

Synchronization
FieldSynchronization Break

0,2ms/Div.

Identifier
Field

10

T

SSP286/073

Local Interconnect Network Data Bus

Message Contents (Response)

The LIN slave control module adds
information to a message with slave
response based on identifiers.

Example:

For a data request message from the
master, the master control module adds
the response.

Depending on the identifier, the applicable
LIN slave control modules use the data to

perform functions.

Example:

LIN Master Control Module
Climatronic Control Module J255

LIN Master Control Module
Climatronic Control Module J255

Inquiry about Fan Speed

Speed = 150 RPM

LIN Slave
Control Module 1
Heated Windshield
Control Module J505

LIN Slave
Control Module 2
Control Module for Fresh
Air Blower J126 Reports
Actual Fan Speed

SSP286/026

LIN Slave
Control Module 1
Heated Windshield
Control Module J505

Set Fan Speed

Speed = 200 RPM

LIN Slave Control Module 2
Control Module for Fresh
Air Blower J126 Increases
Fan Speed to 200 RPM

SSP286/062

11

Local Interconnect Network Data Bus

2V/Div. =

2V/Div. = 2ms/Div.

Recessive

0,5ms/Div.

T

Response

Master Message

The response consists of 1 to 8 data fields.
One data field consists of 10 bits. Each data
field consists of one dominant start bit, a
data byte that contains the information, and
one stop bit. The start- and stop-bits are
used for the after-synchronization to avoid
transmission errors.

SSP286/074

Sequence of the Messages

The LIN master control module sends the
headers as well as the responses to master
messages on the LIN data bus according to
a specified sequence and cycle.

Information that is used frequently is
sent frequently.

The sequence of the messages can change
depending on the prevailing conditions of
the LIN master control module.

Example of prevailing conditions:

Dominant

12

Header
Without
Response

• Ignition on or off

• Diagnostics active or inactive

• Parking lights on or off

T

Slave
Message
Indicated
by Different
Dominant
Levels

SSP286/075

To reduce the variety of LIN master
control modules, the LIN master control
module sends the headers through the
LIN data bus addressed to all of the
applicable control modules for a fully
equipped vehicle.

Since there may be control modules
addressed that are not installed on a
specific vehicle, headers for these
messages will be shown on the
oscilloscope without responses.

This does not affect the functioning of
the system.

Local Interconnect Network Data Bus

Theft Protection

Data transmission on the LIN data bus
only occurs when a LIN master control
module sends a header with the
applicable identifier.

Manipulation through a LIN wire from
outside the vehicle is impossible because
of the complete control of all messages by
the LIN master control modules. The LIN
slave control modules can only answer.

Left Heated Door Lock
Control Module J210

For example, the doors cannot be opened
by tapping into the LIN data bus because of
this limitation.

With this arrangement, LIN slave control
modules can also be installed on the
outside of the vehicle. The Garage Door
Opener Control Module J530 can be
located in the front bumper for example,
without compromising the security of the
vehicle or the garage.

Laptop Computer

Door Control Module,
Driver Side J386

Vehicle Electrical
System Control
Module 2 J520

Data from
Laptop Computer
Not Understood

Attempted
Manipulation

Garage Door Opener
Control Module J530

SSP286/065

13

Local Interconnect Network Data Bus

Diagnosis

The diagnosis of the LIN data bus system is
done with the Address Word for the
relevant LIN master control module.

The transfer of diagnostic data from the LIN
slave control modules to the LIN master
control module occurs on the LIN data bus.

Example of Diagnosis Capabilities

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lortnoCnaF:elpmaxE

All of the On-Board Diagnostic (OBD)
functions are available for LIN control
modules.

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emitdeificepsanihtiweludomlortnocevals

erawtfosehtotnidemmargorpsitahtlavretni

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14

Introduction

Fiber-Optic Data Bus

In addition to the well-known CAN data bus
systems, a fiber-optic data bus system is
installed for the first time in the 2003
Audi A8.

This data bus system is based on standards
determined by Media-Oriented Systems
Transport (MOST) cooperation. To establish
these standards, several automobile
manufacturers, their suppliers, and
software manufacturers have joined
together to make a unified system for rapid
data transmission possible.

SSP286/007

DVD Video

The MOST standards developed by
this cooperative effort have resulted in a
network specifically designed to relay
media-oriented data. Contrary to what
happens on a CAN data bus, the fiber-optic
data bus based on the MOST protocol
allows address-oriented messages to be
sent to a specific recipient.

This technology is used in
Audi vehicles for data transmission
in the infotainment system.

The infotainment system offers a
variety of modern information and
entertainment media.

DAB Digital Radio

TV Reception

Internet
E-mail

Central
Display and
Operation

Minidisc / CD Audio

Cell Phone
Telematics

CD / DVD
Navigation

SSP286/008

15

Fiber-Optic Data Bus

Transmission Rates of Media

Optical data transfer makes complex
infotainment systems possible because
CAN data bus systems cannot transfer data
fast enough and cannot handle the amount
of data that is needed.

Using video and audio applications requires
data transmission rates of many megabits
per second.

2.2 Mbit/s

0.43 Mbit/s

The transmission of a digital TV signal alone
requires a transmission speed of about 6
megabits per second.

The MOST fiber-optic data bus
allows for transmission rates of

21.2 megabits per second.

5.94 Mbit/s

4.4 Mbit/s

4.4 Mbit/s

1.54 Mbit/s

Navigation

Phone

Video

Video Reduced

1.54 Mbit/s

1.54 Mbit/s

Audio Source 1 (Stereo)
Example: Via Earphones, Right Rear

Audio Source 2 (Stereo)
Example: Via Earphones, Left Rear

Audio Source 3 (Surround Sound)
Example: Via Digital Sound System

Open

SSP286/010

16

Until recently, information such as video
and sound could only be transmitted as
analog signals. This required additional
wiring in vehicle wiring harnesses.

The data transfer of a CAN data bus
system is restricted to a maximum speed
of 1 megabit per second. This explains why
only control signals can be transmitted
using the CAN data bus.

Using the MOST fiber-optic data bus, the
data exchange between the participating
components is digital.

The data transfer using light waves
allows for a much higher data transfer rate.
It also saves wiring and reduces total
vehicle mass.

Fiber-Optic Data Bus

TV Tuner R78

Sound

Video

CAN Data Bus

SSP286/002

In comparison with radio waves, light
waves have very short wave lengths, they
do not produce electro-magnetic
interference waves, nor are they affected
by them.

Light waves make reliable high speed
data transfer rate possible,
with good resistance
to interference.

TV Tuner R78

Digital Sound
System Control
Module J525

Multimedia
Control
Head E380

Front Information
Display Control
Head J523

SSP286/003

17

Fiber-Optic Data Bus

Control Module Design

Fiber-Optic Cable and Connector

The light signals travel through these
connectors to the control module or guide
the produced light signals to the next
component on the fiber-optic data bus.

Electrical Connector

The input and output signals to the control
module are provided through this
connector. It also provides the voltage
supply for the ring break diagnosis
(explained starting on page 44).

Fiber-Optic
Cable Connector

Fiber-Optic Cable

Internal Power Supply

The voltage supplied to the control module
through the electrical connector is
distributed by the internal power supply to
the various control module internal
components. The internal power supply can
turn off these internal components to
reduce power consumption when the
control module is in the sleep mode.

Internal
Power Supply

Electrical
Connector

Light-Emitting
Diode (LED)

Fiber-Optic Transceiver

Photodiode

MOST Transceiver

Diagnosis

Equipment­Specific
Component

Microprocessor

SSP286/011

18

Fiber-Optic Transceiver

The fiber-optic transceiver uses a
photodiode to change light signals received
through the fiber-optic cable into a voltage
that is then transmitted to the MOST
transceiver in the control module.

It also uses a light emitting diode (LED) to
convert voltage signals received from the
control module MOST transceiver into light
signals so that they can be passed on to
the next control module in line on the
fiber-optic data bus.

Fiber-Optic Data Bus

SSP286/063

The produced light waves have a
wavelength of 650 nanometers (nm) and
are visible as red light.

The data are transmitted through
modulation of the light waves.

This modulated light is transmitted
to the next control module through the
fiber-optic cable.

MOST Transceiver

As the name implies, the MOST transceiver
consists of both a transmitter and a
receiver.

The transmitter sends messages as voltage
signals to the fiber-optic transceiver.

The receiver takes the voltage signals from
the fiber-optic transceiver and transmits the
needed data to the control module
microprocessor.

Wavelength
400 nm

Ultraviolet

Wavelength
650 nm

Infrared

SSP286/004

Messages from other control modules that
are not needed by this control module are
guided through the transceiver without
transmitting any data to the
microprocessor. These unchanged
messages are routed back through the
fiber-optic transceiver and transmitted to
the next control module.

19

Fiber-Optic Data Bus

Microprocessor

The microprocessor is the central
processing unit for the control module. It
controls all the important functions of the
control module.

Equipment-Specific Component

The equipment-specific component
controls functions that are unique to the
individual control module, such as operating
the CD-drive or the radio tuner.

Light Beam

P-Layer
(Positively
Charged
Material)

P-N
Junction
(Restrictive
Layer)

N-Layer
(Negatively
Charged
Material)

Electrons

0

V

Contact Ring
(Anode –
Positive
Terminal)

Metal Plate
(Cathode –
Negative
Terminal)

SSP286/048

Photodiode

The photodiode converts light waves into
voltage signals.

Photodiode design

The photodiode has a P-N junction that is
affected by light.

Because the P-layer (positively charged
semiconductor material) is so heavily
“doped” with the impurity that gives it its
positive charge, the restrictive layer or
depletion region at the P-N junction reaches
almost into the N-layer (negatively charged
semiconductor material).

The term doped or doping
refers to the addition of
impurities to the semiconductor
material to give it an absence or
excess of electrons, with the
result of a positive or negative
charge to the material.

20

A contact ring on the P-layer provides
the anode or positive terminal of the
photodiode.

The N-layer is applied to a metallic
base plate that acts as the cathode or
negative terminal.

Fiber-Optic Data Bus

Photodiode Function

When visible light or infrared rays penetrate
the P-N junction, the resulting free energy
creates free electrons and holes nearby.
These induce a voltage to pass through the
P-N junction in direct proportion to the
amount of light that is penetrating it.

This means, that the more light reaches the
photodiode, the higher the voltage will be
that flows through it.

This process is called the “internal
photoelectric effect.”

Low Light Level

0

A

R

0

V

SSP286/005

The photodiode is connected in series with

a resistor on the negative side in the
direction of restriction.

If the voltage through the photodiode
increases because more light reaches it,
the voltage drop across the resistor will
also increase. The resulting changes in
voltage effectively translate light signals to
voltage signals.

Intense Light Level

0

A

R

0

V

SSP286/006

21

Fiber-Optic Data Bus

Fiber-Optic Cable

Digital Sound System
Control Module J525

Receiver

K

Transmitter

The fiber-optic cable is used to route the
light waves produced by the transmitter of
one control module to the receiver of
another control module.

The following criteria had to be
considered during the development
of the fiber-optic cable:

• Light waves travel in straight lines and
cannot be bent. The light waves however
have to be guided through the bends of
the fiber-optic cable.

• The distance between the transmitter
and the receiver can be several yards,
therefore attenuation can occur (see
page 26).

• Mechanical stress, vibration, or repairs
must not damage the fiber-optic cable.

• The function of the fiber-optic cable must
be assured during high temperature
fluctuations in the vehicle.

Receiver

Transmitter

Transceiver

Telephone/Telematic
Control Module J526

SSP286/020

For these reasons, the fiber-optic cable
must fulfill the following requirements:

• The fiber-optic cable must conduct the
light wave with little attenuation.

• The light waves must be guided through
the bends of the fiber-optic cable.

• The fiber-optic cable must be flexible.

• The function of the fiber-optic cable must
be assured between -40°F and 185°F
(-40°C to 85°C).

22

Fiber-Optic Data Bus

Fiber-Optic Cable Design

The fiber-optic cable has several layers.
The core is the main part of a fiber-optic

cable. It consists of
polymethylmethacrylate (PMMA), which is
the actual fiber-optic cable. In it, the light
travels according to the principle of total
reflection with almost no loss.

The optically transparent reflective
coating around the core is needed for
total reflection.

The black casing made from polyamide
protects the core from outside light.

The colored outer cover is for identification,
protection against outside damage, and
insulation against temperature.

Colored Outer Cover Black Casing

SSP286/030

CoreReflective Coating

Fiber-Optic Cable Diameter

SSP286/031

23

Fiber-Optic Data Bus

Total Reflection

SSP286/032

Bend Radius > 1 inch (25 mm)

Transmission of Light Waves
in Fiber-Optic Cables

Straight fiber-optic cable

The fiber-optic cable guides part of the light
waves in a straight line through the core.

The largest part of the light waves are
guided through the fiber-optic cable in a
zigzag line according to the principle of total
reflection against the surface of the core.

Bent fiber-optic cable

The light waves are reflected by total
reflection at the borderline of the core
coating and with that are guided through
the bend.

Bend Radius < 1 inch (25 mm)

SSP286/033

SSP286/034

Total reflection

When a light wave strikes a boundary
layer between a dense and an optically
thin material at a low angle, the beam
will be reflected completely, causing
total reflection.

The core in the fiber-optic cable is the
optically dense material and the coating the
optically thin material. That way the total
reflection occurs on the inside of the core.

This reflection depends on the angle of the
light wave as it hits the boundary layer. If
this angle is too acute, the light waves will
leave the core and higher loss will result.

This condition occurs when the fiber-optic
cable is bent too much or is kinked.

The bend radius of the
fiber-optic cable must not
be less than 1 inch (25 mm).

24

Connectors

Fiber-Optic Data Bus

To be able to connect fiber-optic cables to
control modules, special optical connectors
are used.

There are arrows on the connector plug
coupling to indicate the signal direction.

The connector housing serves as the
connection to the control module.

Fiber-Optic Cable

The transfer of light occurs between the
face surface of the core and the
transmitter/receiver of the control module.

End sleeves are welded by laser or brass
end sleeves are crimped onto the cable
ends to enable connection of the fiber-optic
cables to the connector plug couplings.

Optical Contact Surface

Signal Directional Arrow

Connector Housing

End Sleeve

Lock

Plug Coupling

SSP286/035

25

Fiber-Optic Data Bus

SSP286/081

Optical face surface

Contamination and scratches on the face
surface of the fiber-optic cable increase
signal losses (attenuation).

To produce a transfer of light waves with
no loss, the face surface must be:

• Smooth

• Perpendicular

• Clean

This condition can only be assured by
using a special cutting tool.

Attenuation in the Fiber-Optic Data Bus

A reduction in the amount or intensity of
the light waves as they are routed through
the fiber-optic cable is a reduction in signal.

To evaluate the efficiency of a fiber-optic
cable, the signal loss must be measured.

This signal loss
is referred to as

attenuation.

The attenuation (A) is measured in
decibels (dB).

A decibel is not an absolute value but a
ratio of two values. This is the reason
that a decibel is not defined as a physical
value. For example, the decibel unit
is used to establish acoustic pressure
or sound volume.

To measure attenuation, it is
calculated from the logarithm of the
ratio of the transmitter output versus
the receiver output.

26

Formula:

Attenuation

value (A)

Example:

10 X log = 3 dB

= 10 X log

20 W
10 W

Fiber-Optic Data Bus

Transmitter

Output

Receiver

Output

Plug Coupling
(Example Attenuation 0.5 dB)

This means that for a fiber-optic cable with
an attenuation value of 3 dB, the light signal
will be reduced by half.

If several components are involved in the
transmission of light signals, the
attenuation values can be added to a total
attenuation value, similar to the resistance
of electrical components that are
connected in series.

Since every control module
in the MOST fiber-optic data bus
always transmits anew, only
the total attenuation value
between two control modules
is of any significance.

Fiber-Optic Cable
(Example Attenuation 0.6 dB)

Plug Coupling
(Example Attenuation 0.3 dB

Total Attenuation Value for
this Example 1.4 dB

SSP286/045

27

Fiber-Optic Data Bus

Causes for increased attenuation
in the fiber-optic data bus

1. The bending radius of the fiber-optic
cable is below the specified limit. If the
fiber-optic cable was kinked or bent by
more than a radius of 1 inch (25 mm),
clouding will appear in the core similar
to the clouding appearing in sharply
bent Plexiglas. In such cases the
fiber-optic cable must be replaced.

2. The casing of the fiber-optic cable
was damaged.

3. The face was scratched.

4. The face is contaminated.

5. The faces are offset (connector housing
broken).

6. The faces are positioned on a bias
(angle fault).

7. There is a gap between the face of the
fiber-optic cable and the contact face of
the control module (connector housing
broken or not locked).

8. The end sleeve is not properly crimped.

28

SSP286/069

Fiber-Optic Cable Handling

The fiber-optic cables
and their components
must be handled
with extreme care.

• Do not crush the fiber-optic cable.
Avoid damage to the casing such as
perforating, cutting, pinching, etc. Do
not step on fiber-optic cables or place
objects on them.

• Do not kink or bend the fiber-optic
cable to a radius of less than 1 inch
(25 mm). By installing kink protection
(corrugated pipe), a bending radius of
more than 1 inch (25 mm) is assured
during installation.

Fiber-Optic Data Bus

Corrugated Pipe
for Kink Protection

• Be mindful of tie-down and contact
points, and use the correct length when
routing fiber-optic cables in the vehicle.

• Prevent contamination of the face

surface with liquids, dust, fuels, etc.
Do not remove the protective cap from
the end of the fiber-optic cable until
just before testing or installation. If the
protective cap is missing, you may have
to replace the fiber-optic cable with
another new one that has been
properly protected.

• Do not apply thermal treatment or repair
methods to fiber-optic cables that involve
soldering, heat bonding, or welding.

• Do not employ chemical or mechanical
methods to connect fiber-optic cables
such as gluing or butt joints.

• Do not twist two fiber-optic cables
together or one fiber-optic cable with a
copper wire.

SSP286/087

29

Fiber-Optic Data Bus

Ring Structure of the
Fiber-Optic Data Bus

An important feature of the MOST
fiber-optic data bus system is its circular
arrangement in the form of a ring.

The control modules send data in one
direction on a fiber-optic cable to the next
control module in the ring.

This procedure is repeated until the data is
again received by the control module that
sent the data in the first place.

This way the ring closes.
The diagnosis of the MOST fiber-optic

data bus system is performed through the
Data Bus On-Board Diagnostic Interface
J533 (Gateway) and diagnosis CAN data
bus to the 16-Pin Connector T16
(Diagnostic Connection).

SSP286/047

30

System Manager

Fiber-Optic Data Bus

The system manager is responsible for
the system management in the MOST
fiber-optic data bus. The system manager
is supported by the diagnosis manager

The Data Bus On-Board Diagnostic
Interface J533 (Gateway) assumes the
diagnosis management function in the Audi
A8 (see page 44).

The Front Information Display Control Head
J523 is responsible for the system
management function.

The system manager is responsible for:

• Control of the system conditions.

• Transmitting messages of the MOST
fiber-optic data bus.

• Control of the transmission capacities.

MOST Fiber-Optic Data Bus
System Conditions

Conditions for activating the sleep mode:

• All control modules in the system signal
their readiness to switch to the sleep
mode.

• There is no request from other bus
systems via the Data Bus On-Board
Diagnostic Interface J533 (Gateway).

• Diagnosis is not active.

Overriding the above conditions,
the system can be switched to the
sleep mode by:

• The Battery Monitoring Control Module
J367 via the Data Bus On-Board
Diagnostic Interface J533 (Gateway)
during discharge of the starter battery.

• When the transport mode is activated
via the Vehicle Diagnosis, Test and
Information System VAS 5051.

Sleep Mode

In the sleep mode there is no data
exchange on the system. The components
are ready but can only be activated by a
start impulse from the system manager
through the fiber-optic data bus.

The sleep mode voltage is
reduced to a minimum.

SSP286/066

31

Fiber-Optic Data Bus

Standby Mode

In this mode there is no service offered to
the operator. It seems as if the system is
turned off. However, the system is active in
the background. All output media (display,
radio amplifier, etc.) are either inactive or
are switched to the standby mode.

The system is in standby mode during the
after-run period and when the vehicle is
being started.

Activation of the standby mode:

• Can be triggered by other data buses via
the Data Bus On-Board Diagnostic
Interface J533 (Gateway), by unlocking
and opening the driver’s door, or turning
the ignition on.

• Can occur through a control module in
the MOST fiber-optic data bus, for
instance by an incoming phone call.

SSP286/067

32

Fiber-Optic Data Bus

Power On

In the power-on mode, all control modules
are turned on. Data exchange occurs on the
MOST fiber-optic data bus. All functions are
available for the operator.

Conditions for activating the power-on
mode:

• The MOST fiber-optic data bus system is

in standby mode.

• Activation through other data buses via

the Data Bus On-Board Diagnostic
Interface J533 (Gateway), for example
S-contact, display active.

• Activation triggered by a function

selection by the operator, such as from
the Multimedia Control Head E380.

Further information about activation
conditions is available in Self-Study
Programs that apply to the specific vehicle.

SSP286/068

33

Fiber-Optic Data Bus

Message Frames

The system manager (Front Information
Display Control Head J523) transmits
message frames to the next control module
in the fiber-optic data bus ring at a duty
cycle frequency of 44.1 kHz.

The stability of this duty cycle
frequency allows the transmission of
synchronous data.

Synchronous data transmit information
such as digital audio and video signals
that must always be sent in the same
time intervals.

The stable duty cycle frequency
of 44.1 kHz corresponds with the
transmission frequency of digital audio
and video equipment such as CD Changer
Unit R41, Video Recorder / DVD Player
R129, and Digital Sound System Control
Module J525. This allows the integration of
such equipment into the MOST fiber-optic
data-bus system.

Construction of a Message Frame

A message frame is 64 bytes long and
subdivided into sections.

One byte contains
eight bits.

Start Field
(4 bits)

Delimitation
Field (4 bits)

Data Field
(480 bits)

Status
Field
(7 bits)

First Control
Byte (8 bits)

SSP286/036

Parity
Field
(1 bit)

SSP286/037

Second Control
Byte (8 bits)

34

SSP286/039

SSP286/040

Fiber-Optic Data Bus

Sections of a Message Frame

The start field, also called the preamble,
marks the beginning of a frame. Each frame
of a block has its own start field.

A delimitation field is used to clearly
separate the start field from the following
data fields.

In the data field, the MOST fiber-optic data
bus transmits up to 60 bytes of usable data
to the control modules.

There are two data types in a
message frame:

• Sound and video as synchronous data.

• Pictures, information for calculation, and

text, as asynchronous data.

The partition of the data field between
the two data types is flexible. The portion
of synchronous data in the data field
is between 24 and 60 bytes. The
transmission of synchronous data has
priority over asynchronous data.

Asynchronous data are registered
depending on the transmitter and receiver
addresses (identifiers), and the available
asynchronous portion, in packages of four
bytes which are then sent to the receiver.

The sequence of the applicable data
transmission is further described starting
on page 40.

Asynchronous Data 0 – 36 Bytes

Synchronous Data 24 – 60 Bytes

SSP286/041

35

Fiber-Optic Data Bus

With the two control bytes, the following
information is transmitted:

SSP286/042

SSP286/038

• The transmitter and receiver address
(identifier).

• The control commands to the receiver
(such as to an amplifier for increasing or
decreasing the volume).

The control bytes of a block are assembled
in the control modules to make up a control
frame. A block consists of 16 frames. The
control frame contains control and
diagnostic data for sending the data from
one transmitter to a receiver. This is called
“address-oriented data transmission.”

Example:

• Transmitter – Front Information Display
Control Head J523.

• Receiver – Digital Sound System Control
Module J525.

• Control signal – increase or
decrease volume.

36

SSP286/043

SSP286/044

The status field of a frame contains
information for transmission of the frame
to the receiver.

The parity field is used to check the
frame for a last time for completeness.
The contents of this field determine
whether a transmission process is going
to be repeated.

Function Flow in the
MOST Fiber-Optic Data Bus

Fiber-Optic Data Bus

System Start (Wake-Up)

If the MOST fiber-optic data bus is in the
sleep mode, the system is first switched to
standby mode by the wake-up procedure.

If a control module other than the system
manager wakes the system, it sends a
specifically modulated light signal, the slave
light signal, to the next control module.

Radio Remote Key

The next control module in the ring
receives the slave light signal by the active
photodiode and passes it on.

This process continues until the signal
arrives at the system manager.

The system manager recognizes the arrival
of the slave light signal as a command to
start the system.

Central Control Module
for Comfort System J393

Recognition of
Light Signal Initiation
of System Start (Wake-Up)

Data Bus On-Board
Diagnostic Interface J533

Light-Emitting
Diode Switched to
Slave Light Signal

System Manager (Front Information
Display Control Head J523)

SSP286/046

37

Fiber-Optic Data Bus

In response to this signal, the system
manager sends a different specifically
modulated light signal, the master
light signal, to the next control module
in the ring.

This master light signal is transmitted by
each control module in turn.

When the system manager receives the
master light signal back at its fiber-optic
transceiver, it recognizes that the fiber-optic
data bus ring has been closed and starts
transmitting the message frame.

Light-Emitting
Diode Switched to
Master Light Signal

Fiber-Optic
Transceiver Recognizes
Closed Ring

System Manager (Front Information
Display Control Head J523)

SSP286/076

38

Fiber-Optic Data Bus

In the first message frame, the control
modules in the MOST fiber-optic data bus
are asked to identify themselves.

Following the identification cycle, the
system manager sends the current
sequence (actual configuration) to all
control modules in the ring.

This makes address-oriented data
transmission possible.

The diagnosis manager compares
the reported control modules
(actual configuration) with a stored
list of the installed control modules
(specified configuration).

If the actual configuration does not match
the specified configuration, the diagnosis
manager (Data Bus On-Board Diagnostic
Interface J533) stores the applicable
Diagnostic Trouble Code (DTC).

At this point the wake-up procedure is
concluded and data transmission can begin.

Message Frames

SSP286/086

System Manager (Front Information
Display Control Head J523) Transmits
Message Frames

39

Fiber-Optic Data Bus

Transmission of Sound
and Video as Synchronous Data

Synchronous data transmission is explained
here using a function of the 2003 Audi A8
audio system as an example: playing a
music CD.

The operator selects the desired title
(10 in this example) on the music CD from
the Multimedia Control Head E380 and the
Front Information Display Control Head
Control Module J685.

The Multimedia Control Head E380
transmits the control data over a data
connection to the system manager (Front
Information Display Control Head J523).

The system manager then adds the
continuously sent frames to a message
block (16 frames) with the control data:

• Transmission address:
— Front Information Display Control

Head J523, position 1 on the MOST
fiber-optic data bus ring.

• Receiver address of the data source:
— CD Changer Unit R41, position on the

ring depending on installed options.

• Control commands:
— Play title 10.

— Assign transmission channels.

The CD Changer Unit R41 (the data
source) decides which bytes in the data
field are available for the transmission of
CD drive data.

Then it adds a block with the following
control data:

• Transmission address of the data source:
— CD Changer Unit R41, position on the

ring depending on installed options.

• Receiver address of the system manager:
— Front Information Display Control

Head J523, position 1 on the ring.

• Control command:
— Data transmission music CD on

channels 01, 02, 03, 04 (stereo).

40

Multimedia Control Head E380

Message Frame
with Control Data from
Digital Sound System
Control Module J525

Selection of
Functions

Fiber-Optic Data Bus

Front Information Display
Control Head J523
(System Manager)

Message Frame
to CD Changer
Unit R41

Message Frame
to Digital Sound
System Control
Module J525

Digital Sound System
Control Module J525
(Data Receiver)

SSP286/077

CD Changer Unit R41
(Data Source)

Message Frame with
Control Data from
CD Changer Unit R41

41

Fiber-Optic Data Bus

Data Management During
Synchronous Transmission

The Front Information Display Control Head
J523 then commands the Digital Sound
System Control Module J525 to play the
music by using a block with the following
control data:

• Transmission address:
— Front Information Display Control

Head J523, position 1 on the MOST
fiber-optic data bus ring.

• Receiver address:

— Digital Sound System Control Module

J525, position on the ring depending
on installed options.

• Control commands:

— Read data channels 01, 02, 03, 04 and

deliver through the loudspeakers.

— Use current sound adjustments, such

as volume, fader, balance, base,
treble, middle.

— Turn off mute.

The data of the music CD remain in the
data field until the frame reaches the
CD Changer Unit R41 (the data source)
again on the ring.

This makes the use of synchronous data
possible for each performance device
(sound package, earphone connections) on
the MOST fiber-optic data bus.

As the system manager, Front Information
Display Control Head J523 assigns which
one of the devices uses the data based on
the applicable control data.

Transmission channels

The transmission of sound or video
requires several bytes in each data field.
The data source reserves a number of
bytes according to the kind of data. The
reserved bytes are called “channels.” Each
channel contains one byte of data.

Number of transmission channels

Signal Channels (Bytes)

Mono 2
Stereo 4
Surround 12

Reserving these channels makes it possible
to simultaneously transmit synchronous
data from several data sources.

Control Module for
Navigation with
CD-Mechanism J401

42

Channel for CD Drive
(Example: Stereo)

Channel for
Voice Presentation
(Example: Mono)

CD Changer Unit R41

Free Bytes
within Data Field

Channel for DVD Drive
(Example: Surround)

Video Recorder /
DVD Player R129

SSP286/078

Fiber-Optic Data Bus

Transmission of Data for Pictures, Text,
and Functions as Synchronous Data

The following data are transmitted as
asynchronous data:

• Map displays of the navigation system.

• Navigation calculations.

• Internet web sites.

• E-mail.
The sources of asynchronous data send

them at irregular time intervals.
For this reason, each source saves its

asynchronous data in an intermediate
memory.

Message Frame with
Data from Control Module
for Navigation with
CD-Mechanism J401

The data source now waits until it receives
a message block with the address of the
receiver.

In this message block, the source enters
the data in the free bytes in the data fields.

This is done in packages of four bytes each
(quadlets).

The receiver reads the data packages in the
data fields and uses the information.

The asynchronous data stay in the data
fields until the message block again
reaches the data source.

The data source selects the data from the
data fields and if necessary, replaces them
with new ones.

Front Information Display
Control Head J523
Display (Data Receiver)

Control Data from
Front Information
Display Control Head J523
Display (Data Receiver)

Control Module for
Navigation with
CD-Mechanism J401
(Data Source)

Navigation
Information
on CD/DVD

Message Frames
with Data from
Telephone/Telematic
Control Module J526

Telephone/Telematic
Control Module J526
with Intermediate
Memory (Data Source)

Internet
Web Sites
and E-mail

SSP286/079

43

Fiber-Optic Data Bus

Diagnosis

Diagnosis Manager

In addition to the system manager,
the MOST fiber-optic data bus has a
diagnosis manager.

The diagnosis manager performs a
diagnosis of the fiber-optic data bus ring
and transmits the diagnosis data of the
control modules in the ring to the scan tool.

The diagnosis function for fiber-optic
data bus in the 2003 Audi A8 is performed
by Data Bus On-Board Diagnostic
Interface J533.

System Failure

If the transmission of data in the fiber-optic
data bus is interrupted, it is referred to as a
“ring break” because of its ring structure.

Reasons for a ring break can include:

• Interruption of the fiber-optic cable.

• Faulty voltage supply of the transmitter
or receiver control module.

• Faulty transmitter or receiver
control module.

To localize a ring break, a ring break
diagnosis must be performed. The ring
break diagnosis is part of the output
diagnostic test mode of the diagnosis
manager.

Consequences of a ring break are:

• Failure of sound and video reception.

SSP286/057

• Failure of control and adjustment using
the Front Information Display Control
Head J523.

• The Diagnostic Trouble Code (DTC)
entered in the diagnosis manager is
“Optical data bus interruption.”

Ring Break Diagnosis
Wiring for ring break diagnosis

Because data transmission in the MOST
fiber-optic data bus is not possible in case
of a ring break, the diagnosis must be
performed using a diagnosis wire.

The diagnosis wire is connected to every
control module in the fiber-optic data bus
ring from a central connection.

44

Fiber-Optic Data Bus

How ring break diagnosis works

After ring break diagnosis is initiated, the
diagnosis manager sends an impulse to the
control modules over the diagnosis wire.

In response to this impulse, all the control
modules in the ring use the transmitters in
their fiber-optic transceivers to send light
signals through the fiber-optic cable.

At the same time all control modules check:

• Their voltage supply and internal

electrical functions.

• The receipt of the light signals from the
previous control module in the ring.

Each control module connected to the
MOST fiber-optic data bus answers
according to timing programmed into the
software.

Using the timing between the start of the
ring break diagnosis and receipt of the
answer, the diagnosis manager recognizes
which control module sent the answer.

The control modules connected to the
MOST fiber-optic data bus send two
messages after the start of the ring break
diagnosis:

• Control module is electrically OK
means that the electrical functions of the
control module, such as the voltage
supply are OK.

• Control module is optically OK means
that it receives the light signal through its
photodiode from the control module that
precedes it in the ring.

From this information the diagnosis
manager can recognize:

• Whether there is an electrical fault in the
system (voltage supply faulty).

• Between which of the control modules
the optical data transmission is
interrupted.

Diagnosis Wire

16-Pin Connector T16
(Diagnostic Connection)

Interruption of the
Fiber-Optic Cable

SSP286/080

45

Fiber-Optic Data Bus

Ring break diagnosis with
increased attenuation

The previously described ring break
diagnosis process can only detect an
interruption of the data flow.

The output diagnostic test mode of the
diagnosis manager (Data Bus On-Board
Diagnostic Interface J533) can also perform
a ring break diagnosis with reduced light
output to recognize a reduction in the
amount or intensity of the light waves as
they are routed through the fiber-optic
cable (increased attenuation).

The process of the ring break diagnosis
with reduced output is similar to the one
described for interrupted data flow.

However, in this case the control modules
switch the LEDs in their fiber-optic
transceivers to an attenuation of 3 dB, or to
half of their normal light output.

If the fiber-optic cable has an increased
attenuation, the light signal is too weak as it
reaches the receiver. The receiver then
reports ”Optics not OK.”

From this signal the diagnosis manager
recognizes the fault location and produces
an appropriate message in the “Guided
fault-finding” mode of the scan tool.

Increased Attenuation
(Caused in this Example by a
Pinched Fiber-Optic Cable)

SSP286/088

46

Introduction

Bluetooth

In the modern business world as well
as in private life, mobile communication and
information is becoming more and more
important.

A person often uses more than
one mobile device such as a mobile
telephone, a personal digital assistant,
or a laptop computer.

The exchange of information between
these mobile devices was possible in the
past only through hard-wired electrical
connection or wireless infrared connection.

These non-standardized connections took
up valuable space and the devices were
complicated to operate.

Cordless Cellular
Telephone R54 in
2003 Audi A8

The Bluetooth technology takes up less
space and reduces the complexity of
operating these devices. It enables mobile
devices of various manufacturers to be
connected through a standardized
radio transmission.

This technology is used for the first
time in the 2003 AUDI A8 for the
wireless connection between the
cordless Cellular Telephone R54 and the
Telephone/Telematic Control Module J526.

Mobile Telephone
(Future Use)

Telephone Baseplate R126

Laptop
Computer
(Future Use)

Telephone/Telematic
Control Module J526

SSP286/085

47

Bluetooth

At a later date other applications are
planned for the vehicle user:

• Installation of a second phone in the rear
passenger compartment.

• Connection of laptop computers,
smart phones, and notepads to the
internet for transmission of information
and entertainment.

• Reception and transmission of e-mail
using a laptop computer or personal
digital assistant.

• Transmission of addresses and phone
numbers from a laptop or personal
digital assistant to the multimedia
interface system.

• The hands-free operation of mobile
phones without additional cable adapters.

• Use of Bluetooth technology in other
vehicle systems (remote operation of the
auxiliary heater for example).

What is Bluetooth?

The Swedish company Ericsson promoted
the development of a standardized short
distance radio transmission system – the
Bluetooth technology.

In response to this initiative, many
companies have joined in the development
of this technology. Today the Bluetooth
Special Interest Group consists of more
than 2000 companies, including
telecommunications, data processing,
equipment, and vehicle manufacturers.

The name “Bluetooth” comes from the
Viking King Harald Blåtand. During the tenth
century he united Denmark and Norway
and had the nickname “Bluetooth.”

Because this transmission system connects
diverse information and data processing
devices as well as mobile phones, the
resulting good communication reflects the
philosophy of King Harald. That’s the reason
it was called Bluetooth.

48

SSP286/084

Design and Function

Bluetooth

The Bluetooth technology enables
wireless connection of various mobile
devices from different manufacturers
using a standardized radio transmission.

In selected mobile devices, short-range
transceivers (transmitters and receivers) are
either directly installed or integrated using
an adapter (example PC-card, universal
service bus, etc.).

The radio transmission occurs in the

2.40 GHz to 2.48 GHz frequency range
that is available worldwide. Transmitting
on this band does not require a license
and is free of charge.

The very short wave length of this
frequency makes it possible to integrate
the following into the Bluetooth module:

• The antenna (Bluetooth Antenna R152).

• The control and encryption.

• The entire transmission and receiver
technology.

The small size of the Bluetooth
module allows its installation into small
electronic devices.

SSP286/082

49

Bluetooth

The Bluetooth data transmission rate is up
to 1 megabit per second. These devices
can transmit up to three language channels
at the same time.

Bluetooth transmitters normally have a
range of about 33 feet (10 meters). In
special applications with amplifiers,
transmission ranges of up to about 330 feet
(100 meters) are possible.

The data transmission works with no
complicated adjustments.

As soon as two Bluetooth devices meet,
they automatically establish a connection.
Before that can happen, the devices must
be adapted once by entering a PIN-number.

With entering the PIN-number, small
transmission cells are formed, called
“piconets,” to help with the organization
of data.

In each piconet, one device assumes the
master function. The Telephone/Telematic
Control Module J526 is the Bluetooth
master in the 2003 Audi A8.

• The master establishes the connection.

• The other devices synchronize with the
master.

• Only the device that received a data
package from the master may send an
answer.

To prevent chaos in the construction of a
piconet, adjustments can be made to every
device to determine whether it will
communicate with another device or not.

Each device has an address that is 48 bits
long and is unique worldwide. This makes it
possible to clearly identify more than 281
trillion devices.

A piconet offers room for a maximum of
eight active Bluetooth devices. Each device
can belong to several piconets at the

same time.

50

Bluetooth

Shared Operating Frequencies

Data transmission in the Bluetooth system
is done using radio waves within a
frequency range of 2.40 GHz to 2.48 GHz.

This frequency range is used also by other
devices:

• Garage door openers

• Microwave ovens

• Medical devices

Interference Reduction Measures

The Bluetooth technology employs special
measures to reduce the interference
caused by other devices operating on the
same frequencies.

Function

2.480 GHz

The Bluetooth control module:

• Divides the data into short and flexible

data packages. They have a duration of
about 625 milliseconds.

• Checks the completeness of the data

packages using a check total of 16 bits.

• Automatically repeats the transmission of

faulty data packages.

• Uses robust language coding. The

language is converted into digital signals.

The Bluetooth transmitter module:

• Changes the transmitting and receiving

frequencies at random, 1600 times per
second. This is called “frequency
hopping.”

Interference from Other
Electronic Devices
(Microwave for Example)

1 MHz

Transmitting Range

(79 Channels @ 1 MHz)

2.402 GHz
625 Milliseconds

Minimum

Time

Master Message (Inquiry)
Slave Message (Answer)

SSP286/083

51

Bluetooth

Diagnosis

Data Security

In the development of the Bluetooth
technology, the cooperating manufacturers
placed great value on the protection of the
transmitted data against manipulation and
unauthorized access.

The data are encrypted using an encryption
key that is 128 bits long.

The receiver is checked for authenticity
with a key of 128 bits. The devices use a
secret password that is used for
participants to recognize each other.

The key is newly created for
every connection.

Since the range is limited to about 33 feet
(10 meters), a manipulation must occur
within this range. This also increases
data security .

These same measures also increase
security against outside interference and
manipulation of the data flow.

By additional use of elaborate encrypting
methods, diverse security levels, and
network protocols, the equipment
manufacturers can increase data security
even further.

The diagnosis of the Bluetooth connection
is performed using the Address Word of
the master control module.

The Telephone/Telematic Control
Module J526 is the Bluetooth
master in the 2003 Audi A8.

Address Word 77 – Phone
Address Word 75 – Emergency
call module

The Bluetooth connection between the
Cordless Cellular Telephone R54 in the
2003 Audi A8 and the Telephone/Telematic
Control Module J526 is monitored by the
Bluetooth Antenna R152.

If an interruption in the connection to the
Bluetooth Antenna R152 occurs, the
following Diagnostic Trouble Code (DTC) is
put into memory:

“Bluetooth antenna – no signal / no
communication”

In the measured value blocks the portable
devices that are connected to the master
control module can be shown in detail:

• The number of devices.

• The device number.

• The field strength of the
radio connection.

52

In the adaptation of the Bluetooth master,
the Bluetooth function can be turned on or
off. This may be necessary during air
transport of the vehicle or operation of the
vehicle in a country that does not allow the
use of Bluetooth frequencies.

Diagnosis Can Data Bus

Overview

The diagnosis CAN data bus is used for the
data exchange between the diagnostic
scan tool and the control modules installed
in the vehicle.

The K-wires or L-wires are
no longer used, with the
exception of emission-related
control modules.

The diagnosis is performed with the Vehicle
Diagnosis, Test and Information System
VAS 5051 or the Vehicle Diagnosis and
Service Information System VAS 5052.

The transfer of the control module
diagnosis data is accomplished by means
of the applicable data bus systems to the
Data Bus On-Board Diagnostic Interface
J533 (gateway).

Instrument Panel / Gateway
Interface CAN Data Bus

Drivetrain CAN Data Bus

Convenience CAN Data Bus

Distance Regulation
CAN Data Bus

MOST
Fiber-Optic
Data Bus

Diagnosis
CAN Data
Bus

Taking advantage of the rapid data
transmission through the diagnosis CAN
data bus and the gateway function, the

diagnostic scan tool is able to show the
status of installed components and their
fault status.

The diagnosis CAN data bus uses two
unshielded and twisted wires, each with a
diameter of 0.35 mm.

The low diagnosis CAN data bus wire is
orange/brown and the high diagnosis CAN
data bus wire is orange/violet.

The data transfer occurs at a transfer
speed of 500 kilobits per second in the
full duplex mode. That means that data can
be transmitted in both directions at the
same time.

Data Bus On-Board
Diagnostic Interface
J533 (Gateway)

SSP286/012

High Diagnosis
CAN Data Bus Wire

SSP286/055

Low Diagnosis
CAN Data Bus Wire

53

Diagnosis CAN Data Bus

Diagnosis can be done
under the following conditions:

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To initiate diagnosis on the
vehicle, one of these new
diagnostic cables is required:

VAS 5051/5A – 9.8 ft (3 m)
or

VAS 5051/6A – 19.7 ft (6 m)

These new diagnostic cables can also be
used with diagnosis systems using K-wires

SSP286/056

or L-wires.

VAS 5052

Vehicle Diagnosis and Service Information System
Version -D- / V01.02 20/08/2001

Print Help

54

Vehicle Self­Diagnosis

Elsa Win

Applications

Administration

SSP286/051

The latest version of the
software is needed for diagnosis:

VAS 5051 – Basic software

3.0 for diagnosis
via CAN.

VAS 5052 – Basic software.

With the changes of the basic software
there will be new functions and changes of
the user/system interface.

Extension of Addressing Forms

In addition to directly addressing individual
control modules, it is now possible to
address them in groups. This allows the
DTC memories of several control modules
to be read at the same time.

Therefore, the reading of DTC memories
can be done much faster.

Diagnosis CAN Data Bus

Selective Output Diagnostic
Test Mode Test

The selective output diagnostic test mode
test allows for direct activation of actuators
without staying within a particular sequence.

The simultaneous display of measured
value block control modules is also possible
when checking switches and sensors.

These innovations open new possibilities in
guided troubleshooting.

Guided Fault Finding
Function / Component Selection

Actuator test selective, -J520 SG2
Electrical System

Test
With this actuator test program, individual

actuators of the control module 2 for electrical
system can be triggered selectively in case they
are installed and were coded.

Test
Instruments

Guided Fault Finding
Function / Component Selection

Actuator test selective, -J520 SG2
Electrical System

Actuator inquiry 1 to 6
Which actuator do you want to trigger?

Actuator selection 1 to 6

1. MMI-Display retracting turning mechanism

2. MMI-Display extend turning mechanism

3. K158D 90% Dimming interior light

4. Servotronic full steering assist

5. Servotronic no steering assist

6. SRA extend right lift nozzle

Vehicle Self­Diagnosis

Audi
Audi A8 USA/CDN 1997>
2003 (3)
Sedan
AYS 4.2 Liter Motronic / 265 kW

Go to

Print

Audi
Audi A8 USA/CDN 1997>
2003 (3)
Sedan
AYS 4.2 Liter Motronic / 265 kW

V03.13 20/08/2002

Ready

First function
Description

Help

SSP286/089

V03.13 20/08/2002

Ready

-1-

-2-

-3-

-4-

-5-

-6-

Return

First function
Description

Test
Instruments

Vehicle Self­Diagnosis

Go to

Print

Help

SSP286/090

55

Diagnosis CAN Data Bus

Example:

Guided Fault Finding
Function / Component Selection

Select function or component

With Measuring value / messages

Active actuator:
MMI Display extending turning mechanism

Measuring values / Messages:
Stop switch MMI open: not activated
Stop switch MMI closed: activated
MM-motor: not active

Continue with ©

Test
Instruments

Vehicle Self­Diagnosis

Go to

Audi
Audi A8 USA/CDN 1997>
2003 (3)
Sedan
AYS 4.2 Liter Motronic / 265 kW

Print

V03.13 20/08/2002

First function
description

Help

SSP286/091

The illustration shows the selective output
diagnostic test mode test for checking
the display mechanism of the Vehicle
Electrical System Control Module 2 J520
in the 2003 Audi A8.

Pin assignment at the
16-Pin Connector T16
(Diagnostic Connection)

Pins not listed are not currently in use.

56

SSP286/052

Pin Wiring

1 Terminal 15
4 Ground
5 Ground
6 High Diagnosis CAN Data Bus
7 K-Wire
14 Low Diagnosis CAN Data Bus
15 L-Wire
16 Terminal 30

Knowledge Assessment

An on-line Knowledge Assessment (exam) is available for this SSP.

The Knowledge Assessment may or may not be required for Certification.

You can find this Knowledge Assessment at:

www.accessaudi.com

From the accessaudi.com homepage:

Click on the “ACADEMY” Tab –
Click on the “Academy Site” Link –
Click on the ”CRC Certification” Link –

Knowledge Assessment

For assistance, please call:

Audi Academy

Learning Management Center Headquarters

1-877-AUDI-LMC (283-4562)

(8:00 a.m. to 8:00 p.m. EST)

iii

Audi of America, Inc.
3800 Hamlin Road
Auburn Hills, MI 48326
Printed in U.S.A.
December 2002