BMW-Bus Systems PDF

Table of Contents
Bus Systems
Subject
Page
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Advantages of Bus Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Types of Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Analog Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Analog Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Digital Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Binary Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Signal Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Coded Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Bit and Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Larger Units of Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Overview of Bus Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Main Bus Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Sub-bus Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Main Bus Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
K-CAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Advantages of CAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Terminating Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
K-CAN 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
PT-CAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
PT-CAN 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
ICM-CAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
FlexRay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
FlexRay in E7x Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Wake-up and Sleep Characteristics . . . . . . . . . . . . . . . . . . . . . . . .28
Measurements on the FlexRay . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
FlexRay - Application in F0x Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . .31
Properties of FlexRay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Bus Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
FlexRay Bus Topology on F0x Vehicles . . . . . . . . . . . . . . . . . . . . . . . .35
Bus Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
Transmission Medium - Signal Properties . . . . . . . . . . . . . . . . . . .38
Deterministic Data Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Bus Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
High Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Initial Print Date: 07/10
Revision Date: 09/11
Subject
Page
Ethernet - Faster Programming Access . . . . . . . . . . . . . . . . . . . . . . . . . .42

Ethernet in F0x Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Features of Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Functions of Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Fiber Optic Bus Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
Principle of Optical Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
Principle of Light Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
Light Attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
Causes of Excessive Attenuation . . . . . . . . . . . . . . . . . . . . . . . . . .47
Service Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
Cable Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
Fiber Optic Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
MOST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
MOST Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Ring Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Connection of Control Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
Fiber Optic Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
MOST Control Units and Light Direction . . . . . . . . . . . . . . . . . . . . . . .57
Light Direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Registration of control units in the MOST . . . . . . . . . . . . . . . . . . . . . .58
Bandwidths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
MOST Bus Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60
Optical Wave Guide Communication Fault . . . . . . . . . . . . . . . . . .60
Control Module Does Not Switch Off Light . . . . . . . . . . . . . . . . .61
Network Wakeup Unsuccessful . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
Ring Break Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
Light Output Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
Ring Break Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
Status Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
Sub-busSystems ............................................66
K-Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
LIN-Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
LIN V2.0 (or V2.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
D-Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
D-CAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
Bit-serial Data Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Local-CAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Gateways ...................................................74
Gateway Rules Based on the Example of a Train Station . . . . . . . . . . .75
Subject
Page
BLANK
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BusSystems
Model:All
Production:All
After completion of this module you will be able to:

Describe the operation of a basic bus system.
Understand how signals and sensor information are shared between
control units in a bus system.
Identify the different bus systems currently used in BMW Group vehicles.
Understand how bus networking technology is applied in BMW vehicles.
Understand diagnostic techniques.
4
Bus Systems
Introduction
Today's vehicles contain a wide variety of electronic devices and components. The total
number of electronic components in motor vehicles is sure to increase substantially in
the foreseeable future. Legislation as well as customers demand this continued development. Legislation is interested in improving the quality of exhaust emissions and reducing fuel consumption. Customer requirements are focussed on improving driving comfort and safety.
Control units that meet these requirements have long been utilized. Examples include
control units employed in the area of the digital motor electronics and airbag systems.
The complexity of the realized functions calls for data exchange between the control
units. Conventionally, the data is transmitted via signal lines. However, in view of the
increase in complexity of the control unit functions, this type of data exchange can now
be realized only with ever growing expenditure.
Originally autonomous processes of individual control units are being coupled to an ever
increasing extent via bus systems. This means that the processes are distributed, implemented throughout the vehicle systems network and interact in co-ordinated functions.
The data exchange within the systems network is therefore constantly increasing. This
data exchange also enables many new functions, which benefit increased road safety
and enhanced driving comfort.
These requirements can no longer be realized with the previous vehicle electrical
systems and networks.
The increasing use of electrical and electronic components in motor vehicles is limited
by various factors:
Increasing scope of wiring/cabling
Higher production costs
Increased space requirement in the vehicle
Component configurations that are difficult to manage
Reduced reliability of overall system
Networks are used in the vehicle electrical system with the aim of minimizing these disadvantages. These networks are referred to as bus systems.
Bus systems enable networking of the individual control units in the vehicle via "serial
interfaces". This provides various advantages that facilitate the use of the systems in
motor vehicles.
5
Bus Systems
AdvantagesofBusSystems
Higher reliability of overall system
Reduced extent of wiring/cabling
Reduction in the number of individual cables
Reduced cross sections of wiring harnesses
Flexible installation of cables
Multiple use of sensors
Transmission of complex data possible
Higher flexibility for system modifications
Expansion of scope of data possible at any time
Implementation of new functions for the customer
Efficient diagnosis
Lower hardware costs
TypesofTransmission
AnalogTransmission
The term analog comes from the Greek (analogos) and means corresponding to, analogous to.
Analog representation of data (= information) is based on representation by a continuously changing physical variable that is directly proportional to the data.
6
Bus Systems
Index
Explanation
Maximum
Voltage
Time
AnalogSignal
A characteristic of an analog signal is that it can assume any value between 0% and
100%. The signal is therefore infinitely variable.
Examples: Pointer measuring instruments, mercury thermometer, hands of a watch.
When listening to music, for example, the ear receives the analog signals (constantly
changing sound waves). This sound is represented in the same way in electrical devices
(audio system, radio, telephone etc.) by means of continuously changing voltages.
However, when such an electrical signal is transferred from one device to another, the
information arriving at the receiver is no longer exactly the same as what was sent by
the transmitter.
This is due to interference factors such as:
Cable length
Line resistance of the cable
Radio waves
Mobile radio signals
The analog transmission of information in vehicle applications is not feasible for safety
and reliability reasons. In addition, the changes in voltages would be much too small so
that reliable values could not be represented (ABS, airbag, engine management etc.).
DigitalTransmission
The term digital originates from the Latin world digitus and means finger or toe.
Digital is therefore everything that can be counted on a few fingers or put more accurately
everything that can be divided into discrete steps.
Index
Explanation
Voltage
Time
7
Bus Systems
Digital representation involves the representation of constantly changing variables in

numerical form. Particularly in computers, all data are represented as a sequence of
zeros and ones (binary). Digital is therefore the opposite of analog.
Examples: Digital multimeter, digital clock, CD, DVD.
BinaryTransmission
The word bi comes from the Greek and means two.
BinarySignal
Index
Explanation
Index
Explanation
High
Voltage
Low
Time
A binary signal therefore has only two possible states: 0 and 1 or High and Low.
Examples:
Lamp lights - lamp does not light
Relay has dropped out - relay has picked up
Voltage is applied - voltage is not applied
All symbols, images or even sounds consist of a certain series of binary characters such
as 10010110. With this binary code, the computer or the control unit can process information or send the information to other control units.
8
Bus Systems
SignalLevel
In order to be able to clearly distinguish between the two states High and Low in
motor vehicle applications, a clearly defined range is assigned to each state:
The High range is between 6 V and 12 V
The Low range is between 0 V and 2 V
The range between 2 V and 6 V is the so called prohibited range that is used for fault
detection purposes.
CodedRepresentation
Signallevel
Index
Explanation
Index
Explanation
High range
Voltage
Prohibited range
Time
Low range
A code is a distinct set of rules for depicting a character set in another character set.
An example of a code is the Morse alphabet. Each letter of the alphabet and the numbers
are encrypted by signals of different lengths.
9
Bus Systems
In Morse code, the well-known distress signal SOS (save our souls) is:
shortshortshort
longlonglong
shortshortshort
The code is used to convert information that is represented in encrypted form into another form of representation where the information content is not changed.
Important codes in computer engineering are ASCII and hexadecimal code.
For example, a person using a computer presses the D key on the keyboard. The letter D
is then represented (coded) as a binary sequence 0100 0100. This character sequence
is then sent in the form of an electrical signal from the keyboard via the cable to the computer. The computer interprets (decodes) this character sequence correctly as the letter D.
The character sequence and its electrical signal are known as coded information.
BitandByte
All information in computers is stored as bits (binary digit = smallest information unit).
All data (letters, numbers, sounds, images etc.) must therefore be converted into a binary
code for processing in the computer.
The most commonly used systems and codes use eight bits for the purpose of representing a character.
Eight bits are combined to form one byte, allowing 256 characters to be coded.
LargerUnitsofBytes
The conversion does not correspond exactly to the factor 1000 but rather the factor
1024.
1 Kilobyte (KB) = 210 bytes, i.e. 1024 bytes
1 Megabyte (MB) = 220 bytes, i.e. 1024 KB (1.048.576 bytes)
1 Gigabyte (GB) = 230 bytes, i.e. 1024 MB (1.073.741.824 bytes)
10
Bus Systems
OverviewofBusSystems
In principle, a distinction is made between two groups of bus systems:
Main bus systems
Sub-bus systems
Main bus systems are responsible for cross system data exchange. Sub-bus systems
exchange data within the specific system. These systems are used to exchange relatively
small quantities of data in specific systems.
MainBusSystems
The following busses are used as main bus systems:
Mainbussystem
Datarate
Busstructure
K-Bus*
9.6 kbits/s
Linear -one-wire
D-Bus
10.5 - 115 kbits/s
Linear - one-wire parallel
CAN
100 kbits/s
Linear - two-wire parallel
D-CAN
500 kbits/s
K-CAN
100 kbits/s
K-CAN 2
500 kbits/s
F-CAN
500 kbits/s
PT-CAN
500 kbits/s
PT-CAN 2
500 kbits/s
byteflight
10 MBits/s
Star structure - fiber optics conductor
MOST
22.5 MBits/s
Ring structure - fiber optics conductor
FlexRay
10 MBits/s
Star- two wire
* Also known to as I-Bus in earlier models
Sub-busSystems
The following busses are used as sub-bus systems:
Mainbussystem
Datarate
Busstructure
K-Bus protocol
9.6 kbits/s
Linear - one-wire
BSD
9.6 kbits/s
Linear - one-wire
DWA-Bus
9.6 kbits/s
Linear - one-wire
LIN-Bus
9.6-19.2 kbits/s
Linear - one-wire
11
Bus Systems
E70BusOverview
12
Bus Systems
MainBusSystems
K-CAN
K-CANontheE90
K-CAN stands for Karosserie (body) Controller

Area Network. CAN was developed by Robert
Bosch GmbH as the bus system for motor vehicles.
The task of the K-CAN is to transmit information
in the area of the vehicle body.
As a twisted two-wire copper line, the K-CAN
operates at a transmission rate of 100 kbits/s.
A further bus in the CAN family is the F-CAN.
F-CAN stands for Fahrwerk (chassis) Controller
Area Network. This bus is structured and functions in exactly the same way as the K-CAN.
However, the F-CAN is used exclusively for data
transmission of the chassis/suspension components such as the dynamic stability control for
example.
F-CANontheE90
13
Bus Systems
AdvantagesofCAN
The advantages of the CAN-Bus are:
Higher data transmission speed compared to conventional wiring
Improved electromagnetic compatibility (EMC)
Improved emergency operation characteristics
The body controller area network, abbreviated K-CAN, is used in BMW vehicles to interlink components of the comfort and body electronics such as lamp control, seat adjustment and air conditioning.
The transmission rate is 100 kbits/s.
K-CAN is based on linear topology, i.e. it conforms to a bus structure.
Each terminal unit (node, control unit) in a network with a bus structure is connected with
a common line.
The K-CAN is a multi-master bus. Each control unit that is connected to the bus can
send messages.
The control units communicate event controlled. The control unit wishing to send data
sends a message when the bus is free. If the bus is not free, the message with the highest priority is sent.
Since there are no receive addresses, each control unit receives every sent message.
Consequently, further receiver stations can be easily added to the system during operation. Neither the software nor the hardware needs to be changed.
Two-wire copper lines are currently used for data transmission. However, solutions based
on glass fiber or plastic fiber optics conductors are also possible. Fiber optics conductors
are sensitive to high temperatures as occur in the engine compartment. Both lines are
twisted to minimize interference.
14
Bus Systems
The advantage of using two-wire lines is that it is possible to fall back on a one-wire line
in the event of a fault.
Advantages:
Easy to install
Easy to expand
Short lines
Emergency operation on one line
Disadvantages:
Network expansion limited
Intricate access methods
TerminatingResistor
From an electrical point of view, a current carrying conductor always has an ohmic, inductive and capacitive resistance. When transmitting data from point "A" to point "B", the
total sum of these resistances has an effect on data transmission. The higher the transmission frequency, the more effective the inductive and capacitive resistance. Ultimately,
it is possible that a signal, which is no longer identifiable, is received at the end of the
transmission line. For this reason, the line is "adapted" by terminating resistors, ensuring
the original signal is retained.
Inductive resistance occurs, for example, as the result of the coil effect in the line.
Capacitive resistance occurs, for example, by installing the line parallel to the vehicle body.
The terminating resistors used in a bus system vary.
They generally depend on the following parameters:
Frequency of data transmission on the bus system
Inductive or capacitive load on the transmission path
Cable length for data transmission
The longer the line, the greater the inductive component of the line.
The control units are divided into basic control units that are always installed (e.g. instrument cluster in the E9x vehicles) and the remaining control units. The resistance value
determines this division.
Terminating resistors are used to ensure exact signal progression in the bus systems.
These terminating resistors are located in the control units of the bus systems.
If the voltage level changes due to a defective terminating resistor. This change in voltage
affects the CAN system. Communication between the bus users no longer operates correctly.
15
Bus Systems
Voltage level on the K-CAN:

Logic 0 is when the voltage level changes
back to low.
Logic 1 state is assumed when the voltage
level of the CAN-High switches from low to
high.
The voltage difference between the CAN-H and
CAN-L lines is 3 V when a dominant bit is transmitted on the K-CAN.
In order to obtain a clear idea of whether the CAN-Bus is functioning properly, you must
be able to observe activity on the bus. You do not need to analyze the individual bits; you
simply need to observe whether or not the CAN-Bus is working. The oscilloscope test
can state that, the CAN-Bus is probably operating without faults.
CH1:Probetip1,range2V/Div;
DCcoupling
CH2:Probetip2,Range2V/Div;
DCcoupling
Time:100s/Div
When you measure the voltage between the K-CAN Low line (or K-CAN High line)
and the ground, you receive a rectangle-like signal in the following voltage ranges:
Voltage measurement at the K-CAN are:
K-CAN Low to ground: V min = 1 volts and V max = 5 volts
K-CAN High to ground: V min = 0 volts and V max = 4 volts
NodefinedresistancetestcanbecarriedoutontheK-CANdatabus
astheresistancevariesgenerally>720K dependingontheinternal
switchinglogicofthecontrolunits.
16
Bus Systems
The K-CAN is operated as a one-wire bus if:

There is a break in a CAN data line (core)
There is a short to ground on a CAN data line (core)
There is a short to the supply voltage UB+ on a CAN data line (core)
The bus systems used to date are also used in the F01/F02. The K-CAN is responsible
for communication of the components with a low data transfer rate. The K-CAN is also
connected to the other bus systems via the central gateway module.
The K-CAN is set up as line topology. Some control units in the K-CAN have a LIN-Bus
as sub-bus. The K-CAN has a data transfer rate of 100 kBit/s and is designed as a twisted pair of wires. The K-CAN has the possibility to be operated as a single-wire bus in the
event of a fault.
The K-CAN control unit is wakened via the bus, without an additional wake-up line.
The following is an example of the control units which are fitted in the K-CAN of an
F01/F02:
CID Central Information Display
CON Controller
EHC, Electronic Height Control
FD Rear Display
FD2 Rear Display 2
FKA, rear heater / air-conditioning system
HiFi, hi-fi amplifier
HKL, luggage compartment lid lift
HUD, Head-Up Display
IHKA, integrated heater/air conditioning system*
SMBF passenger seat module*
SMBFH rear passenger seat module*
SMFA driver seat module*
SMBFH rear module on driver' seat side*
TPMS, Tire Pressure Monitoring System
TRSVC panoramic camera*
VSW, video switch
ZGM, central gateway module
17
Bus Systems
K-CAN2
First introduced with BN2020 in the F01, the K-CAN 2 is responsible for communication
of the control units with a high data transfer rate. The K-CAN 2 is also connected to the
other bus systems via the central gateway module (ZGM). A LIN-Bus as a sub-bus is
connected to all control units in the K-CAN 2.
The K-CAN 2 can be wakened via any of these sub busses, without an additional (hardwire) wake-up line. This is represented by the wake authorized symbol next to all of the
control units of K-CAN 2 on the Bus Overview. (See bus chart below).
To provide a rapid start enable, the CAS has an additional redundant bus connection to
the DME. On this CAS-Bus, the data are transferred per K-Bus protocol.
The K-CAN 2 is similar to PT-CAN in that it has a data transfer rate of 500 kBit/s, it is
designed as a twisted pair with a measured a resistance of 60 .
The following control units are fitted in the KCAN 2:
CAS Car Access System
FRM, footwell module
FZD, roof functions center
JBE, junction box electronics
PDC, Park Distance Control (integrated in JBE)
ZGM, central gateway module
The terminal resistors in the K-CAN 2 are located in the following control units:
Central gateway module
S
K-CAN2
FRM
CAS
FZD
JB
PDC
18
Bus Systems
ZGM
OBD
Junction box electronics
When you measure the voltage between the K-CAN 2 Low line (or K-CAN 2 High line)
CAN Low to ground: V min = 1.5 volts and V max = 2.5 volts
CAN High to ground: V min = 2.5 volts and V max = 3.5 volts
CH1:Testprobe1,range1V/Div;
DCcoupling
DCcoupling
Time:10s/Div
Values of the terminating resistors on the K-CAN:

2 X 120 resistors which equal a to measured resistance between wires of 60 .
Inspection procedure for resistance test on any CAN-Bus:
The CAN-Bus must be de-energized.
No other testing equipment must be in use (connected in parallel).
The measurement is taken between the CAN Low and CAN High lines.
The actual values may differ from the setpoint values by a few .
In order to prevent signal reflection, 2 CAN-Bus users (at the extremities of the powertrain
CAN network) with 120 each are terminated. The two terminal resistors are connected
in parallel and form an equivalent resistance of 60 . When the supply voltage is switched
off, this equivalent resistance can be measured between the data lines. In addition, the
individual resistors can be tested independently of one another.
Information on the measurement with 60 : Disconnect an easily accessible control unit
from the bus. Then measure the resistance on the connector between the CAN Low and
CAN High lines.
WhenmeasuringK-CAN2voltage,theOscilloscope(IMIB)settings
shouldbethesameasforthePT-CAN,oranyhighspeedCAN.
19
Bus Systems
PT-CAN
E90PT-CAN
PT-CAN stands for Powertrain Controller Area Network.

CAN was developed by Robert Bosch GmbH as the bus
system for motor vehicles.
The PT-CAN has a transmission rate of 500 kbit/s and
prior to the FlexRay was the fastest (hard wire) CAN-Bus
used in BMW vehicles. Most of the busses that were
introduced after it use similar design.
This bus connects all control units and modules belonging to the drive train. All bus users are connected in parallel.
The special feature of this CAN-Bus is that, instead of
two lines, it is equipped with three lines.
The third line is used as a wake-up line and has nothing
to do with actual operation of the CAN-Bus.
DCcoupling
DCcoupling
Time:10s/Div
When you measure the voltage between the PT-CAN Low line (or PT-CAN High line)
Thesevaluesareapproximatevaluesandcanvarybyafewhundred
mVdependingonthebusload.
Note:FormoreinformationregardingCAN-Bussystemdiagnosisreferto:
-SIB610303CAN-ByteflightBusDiagnosis
-FUB-DAA0701FB-656135001CheckingtheCANbussignal
20
Bus Systems
PT-CAN2
Also introduced with BN2020 in the F01 the PT-CAN 2 forms a redundancy for the PTCAN in the area of the engine management system and also transfers signals to the fuel
pump control. PT-CAN 2 is similar to the PT-CAN in that it has a data transfer rate of 500
kBit/s and is designed as a twisted pair with an additional wake-up line. It also
incorporates 2 (120 ) resistors which equal to a measured resistance between the wires
of 60 .
PT-CAN2(F01/F02)
Index
Explanation
DME
Digital Motor Electronics
EKPS
Electronic fuel pump control
EGS
Electronic transmission control
GWS
Gear selector lever
The terminal resistors in the PT-CAN 2 are located in the following control units:
Control unit for electric fuel pump
As with PT-CAN, when you measure the voltage between the PT-CAN2 Low line (or PTCAN 2 High line) and the ground, you receive a rectangle-like signal in the following voltage ranges:
WhenmeasuringPT-CAN2voltage,theOscilloscope(IMIB)
settingsshouldbethesameasforthePT-CANandK-CAN2
(refertotheseforansampleofthePT-CAN2scopepattern).
21
Bus Systems
ICM-CAN
One of the differences between the E71 and the E70 is the introduction of a new control
unit known as Integrated Chassis Management (ICM). The ICM coordinates
longitudinal and lateral dynamic control functions, which include the familiar Active
Steering and the Dynamic Performance Control [with QMVH] Currently available in the
E71 and E70M and E71M.
Despite the fact that the PT-CAN and F-CAN work at a high bit rate of 500 kBps, they
would have been overloaded by the signals from the ICM and QMVH control units. For
this reason,the ICM-CAN sub-bus was introduced.
The ICM-CAN was integrated into the BN2000 network as a new bus system especially
designed for the ICM control unit functions. It connects the ICM, AL and QMVH control
units.
The diagram shows the control units and bus systems that are related for the dynamic
driving systems.
E71buschartwithICM-CANhighlighted
Note:InBN2020vehiclestheICMcontrolunitisconnectedtoanexpanded
versionoftheFlexRayeliminatingtheneedoftheICM-CAN.
22
Bus Systems
The ICM-CAN is a two-wire bus on which data is transmitted at 500 kBps. The two terminating resistors, each with 120 W, are located in the ICM and QMVH control units.
The ICM-CAN cabling in the vehicle varies considerably between the two variants
with/without Active Steering.
If Active Steering is fitted, the ICM-CAN is routed from the ICM control unit to the AL
control unit. The ICM-CAN is picked up in the AL control unit and forwarded to the
QMVH control unit.
If Active Steering is not fitted, the ICM-CAN line is routed directly from the ICM control
unit to the QMVH control unit.
These control units use the ICM-CAN to exchange setpoint values and actual values,
as well as status signals. These signals are only required locally for implementing the
Dynamic Performance Control and Active Steering functions.
In contrast, signals that the dynamic driving systems exchange with other control units
are still transmitted via the PT-CAN. The PT-CAN is also the bus system via which the
ICM, AL and QMVH control units communicate with the diagnostic system.
The ICM control unit does not therefore perform the function of a diagnostics gateway.
As with PT-CAN and K-CAN2, when you measure the voltage between the ICM-CAN
Low line (or ICM-CAN High line) and the ground, you receive a rectangle-like signal in
the following voltage ranges:
WhenmeasuringICM-CANvoltage,theOscilloscope(IMIB)
settingsshouldbethesameasforthePT-CANandK-CAN2
(refertotheseforansampleoftheICM-CANscopepattern).
23
Bus Systems
FlexRay
In the future, driving dynamics control systems, driver assistance systems and their innovative interconnection will be ever more important for the differentiation of the BMW
badge. Since today's networking systems using the CAN-Bus have already reached their
limit, it is necessary to find a suitable alternative for CAN.
In co-operation with Daimler Chrysler AG and the semiconductor manufacturers
Freescale (formerly Motorola) and Philips, BMW AG founded the FlexRay consortium
in 1999 for the purpose of developing innovative communication technology.
The consortium was soon joined by further partners, including Bosch and General
Motors and to date, the Ford Motor Company, Mazda, Elmos and Siemens VDO have
also decided to join. In the meantime, almost all significant car makers and suppliers
throughout the world have joined the FlexRay consortium.
Index
Explanation
Real time capabilities, deterministic (strictly defined) and redundant
Conditional real time capabilities - sufficient for control systems
No real time capabilities
FlexRay is a new communication system which aims at providing reliable and efficient
data transmission with real-time capabilities between the electrical and mechatronic
components for the purpose of interconnecting innovative functions in motor vehicles,
both today and in the future.
24
Bus Systems
Development of the new FlexRay communication system was prompted by the ever
growing technological requirements placed on a communication system for interconnecting control units in motor vehicles and the realization that an open and standardized solution was needed for infrastructure systems.
FlexRay provides an efficient protocol for real-time data transmission in distributed systems as used in motor vehicles.
With a data transmission rate of 10 Mbits/s, the FlexRay is distinctly faster than the data
buses used in the area of the chassis, drive train and suspension of today's motor
vehicles.
In addition to the higher bandwidth, FlexRay supports deterministic data transmission and
can be configured such that reliable continued operation of remaining communication
systems is enabled even in the event of individual components failing.
WhataretheadvantagesofFlexRay?
High bandwidth (10 Mbits/s compared to 0.5 Mbits/s of the CAN)
Deterministic (= real-time capabilities) data transmission
Reliable data communication
Supports system integration
Standard in automotive industry
The FlexRay bus system is an industrial standard and is therefore supported
and further developed by many manufacturers.
25
Bus Systems
FlexRayinE7xVehicles
With the launch of the E70, the FlexRay bus system will be used for the first time
worldwide in a standard production vehicle. The FlexRay bus system establishes the
connection between the VDM control unit (vertical dynamics management) and the EDC
satellites at the shock absorbers. A detailed functional description of the overall system
can be found in the reference information - Vertical Dynamics Systems.
E7xFlexRayBusSystemOverview
26
Bus Systems
LegendforE7xFlexRayBusSystemOverview
Index
Explanation
Junction box control unit
Vertical Dynamics management (VDM)
Diagnosis connector
Ride height sensors, front
EDC satellites with vertical acceleration sensors and solenoid valves
Ride height sensors, rear
D-CAN
Diagnosis CAN
F-CAN
Chassis CAN
PT-CAN
Powertrain CAN
FlexRay
FlexRay bus system
KL 30 g
Terminal 30g
27
Bus Systems
The FlexRay bus system is designed as a two-wire, single-channel bus

system. Acting as the gateway, the VDM control unit establishes the connection
between the PT-CAN and FlexRay bus systems.
Data communication between the EDC satellites on the FlexRay and the other control
units installed in the E70 takes place via the VDM control unit.
Wake-upandSleepCharacteristics
The control units are activated by means of an additional wake-up line. The wake-up line
has the same function as the previous wake-up line (15WUP) in the PT-CAN. The signal
curve corresponds to the signal curve of the PT-CAN.
As soon as the bus system is woken, the VDM receives a High level on the PT-CAN and
transfers this signal to the wake-up line of the FlexRay, thus also waking the satellites.
28
Bus Systems
The "wake-up voltage curve" graphic shows the typical behavior of the voltage curve in
response to unlocking and starting the vehicle.
Phase 1:
Driver unlocks the car, the CAS control unit activates the K-CAN and the PT-CAN, the
voltage level in the PT-CAN briefly goes to High, the VDM copies the signal and transfers
it to the wake-up line on the FlexRay.
Phase 2:
Car is opened, terminal R is still OFF, the voltage levels in the bus systems drop again.
Phase 3:
Car is started, terminal 15 is ON, the voltages remain at the set levels until terminal 15 is
turned off again.
Phase 4:
The complete vehicle network must assume sleep mode at terminal R OFF in order to
avoid unnecessary power consumption. Each control unit in the network signs off to
ensure that all control units "are sleeping". Only when all EDC satellites have signed off
at the VDM control unit can this control unit pass on this information to the PT-CAN and
therefore to the complete network. An error message is stored if this is not the case.
This error message is then evaluated as part of the energy diagnosis procedure.
Wiring
The wiring of the FlexRay bus in E7x vehicles is executed as a sheathed, two-core, twisted cable. The sheathing protects the wires from mechanical damage. The terminating
resistors are located in the EDC satellites. Each satellite has one terminating resistor.
Since the surge impedance (impedance of high-frequency lines) of the lines depends on
external influencing factors, the terminating resistors are precisely matched to the
required resistance.
The four sections of line to the satellites can be checked relatively easily by means of a
resistance measuring instrument (ohmmeter, multimeter). The resistance should be
measured from the VDM control unit. See BMW diagnostic system for pin assignments.
The following conclusions can be made:
RBP-BM:
< or = 10
There is a short circuit in this section of line.
RBP-BM:
10-90
This section of line is damaged

(e.g. moisture in connector, line pinched)
RBP-BM:
90-110
This section of line is OK and the satellite is connected

(Note: Impedance errors are not recognized)
RBP-BM:
> 110
There is a break in the line or the satellite is not connected

or there is a break in the connection to the satellites.
RBP
BM
ResistanceBusPlus
BusMinus
29
Bus Systems
PlugConnections
The two plug connections contain the power supply of

the control units, the wake-up line and the bus connection with wake-up line. The connection to the satellites
in the wheel arch is made with waterproof plugs. Two
plugs are used:
Terminal 30g
Plug 1, black
Terminal 31
Wake-up line
Plug 1, blue
FlexRay (green wire)

FlexRay (pink wire)
MeasurementsontheFlexRay
For resistance measurement in the FlexRay,

be sure to observe the vehicle wiring diagram!
The various termination options mean that misinterpretations of the measurement results
can occur. Measuring the resistance of the FlexRay lines cannot provide a 100% deduction in terms of the system wiring. In the case of damage such as pinching or connector
corrosion, the resistance value may be within the tolerance when the system is static.
In dynamic mode, however, electrical influences can cause increased surge resistance,
resulting in data transmission problems.
It is possible to repair the FlexRay bus. If damaged, the cables can be connected using
conventional cable connectors. Special requirements, however, must be observed when
reinstalling the system.
The wiring of the FlexRay system consists of twisted lines. Where possible, this twisting
should not be altered during repairs. Repaired areas with stripped insulation must be
sealed again with shrink-fit tubing. Moisture can affect the surge resistance and there
fore the efficiency of the bus system.
30
Bus Systems
FlexRay-ApplicationinF0xVehicles
In the F01/F02, the FlexRay bus system was used for the first time across systems to
network dynamic driving control systems and the engine management system in a series
vehicle. The central gateway module sets up the link between the various bus systems
and the FlexRay.
FlexRay-simplifiedview
DME
ZGM
DSC
SZL
HSR
AL
SWW
ICM
VDM
EDC SVL
EDC SVR
EDC SHL
EDC SHR
31
Bus Systems
PropertiesofFlexRay
The most important properties of the FlexRay bus system are outlined in the following:
Bus topology
Transmission medium - signal properties
Deterministic data transmission
Bus protocol
BusTopology
The FlexRay bus system can be integrated in various

topologies and versions in the vehicle.
The following topologies can be used:
Line-based bus topology
Point-to-point bus topology
Mixed bus topology
Line-basedBusTopology
All control units (SG1...SG3) in line-based

topology are connected by means of a twowire bus, consisting of two twisted copper
cores. This type of connection is also used
on the CAN-Bus. The same information
but with different voltage level is sent on
both lines.
Line-basedbustopology
The transmitted differential signal is

immune to interference. The line-based
topology is suitable only for electrical data
transmission.
Point-to-pointBusTopology
The satellites (control units SG2...SG5) in

point-to-point bus topology are each
connected by a separate line to the central
master control unit (SG1). Point-to-point
topology is suitable for both electrical as
well as optical data transmission.
Pointtopointbustopology
32
Bus Systems
MixedBusTopology
Mixed bus topology caters for the use of different topologies in one bus system. Parts of
the bus system are line-based while other parts are point-to-point.
RedundantDataTransmission
Fault-tolerant systems must ensure continued reliable data transmission even after failure
of a bus line. This requirement is realized by way of redundant data transmission on a
second data channel.
Index
Explanation
Channel 1
Channel 2
A bus system with redundant data transmission uses two independent channels.
Each channel consists of a two-wire connection. In the event of one channel failing, the
information of the defective channel can be transmitted on the intact channel. FlexRay
enables the use of mixed topologies also in connection with redundant data transmission.
BusTopologyofFlexRayinE7xVehicles
The physical configuration of the FlexRay bus system in E7x vehicles is point-to-point.
All EDC satellites are individually connected via plug connections to the VDM control unit.
Internally, however, the left and right EDC satellites are connected to form a line-based
topology. The two lines are connected by means of a double point-to-point connection
consisting of two bus drivers. Every item of information that is sent from one of the EDC
satellites or from the central VDM control unit reaches all connected control units.
33
Bus Systems
VDMSystemSchematiconE7xVehicles
Index
Explanation
Index
Explanation
Vertical Dynamics Management (VDM)
Bus driver
EDS satellites, front left
Terminating resistor
EDS satellites, front right
Microprocessor
EDS satellites, rear right
FlexRay
FlexRay bus system
EDS satellites, rear left
34
Bus Systems
FlexRayBusTopologyonF0xVehicles
PhysicalstructureofFlexRayF0x(topology)
35
Bus Systems
LegendforPhysicalstructureofFlexRayF0x(topology)
Index
Explanation
AL
Active steering system
BD
Bus driver
DM
DSC
Dynamic Stability Control
EDCSH
Electronic damper control, rear left satellite
EDCSHR
Electronic damper control, rear right satellite
EDCSVL
Electronic damper control, front left satellite
EDCSVR
Electronic damper control, front right satellite
HSR
Rear-axle drift angle control
ICM
Integrated Chassis Management
SZL
Steering column switch cluster
VDM
Vertical dynamics management
ZGM
FlexRayBusTopologyontheF01
The FlexRay is always shown in a simplified form in the overview of the bus systems. The
actual topology of the FlexRay as used in F0x vehicles is shown in the preceding graphic.
Depending on the level of equipment of the vehicle, the ZGM contains one or two socalled star couplers, each with four bus drivers. The bus drivers forward the data of the
control units via the communication controller to the central gateway module (ZGM).
Depending on the type of termination the FlexRay control units have, they are connected
to these bus drivers in two different ways.
Note:ForfurtherinformationregardingtheFlexRayrefertotheF01training
informationavailableonTISandICP.
BusTermination
In the same way as most bus systems, resistors for termination (as bus termination) are
also used at both ends of the data lines on the FlexRay to prevent reflections on the lines.
36
Bus Systems
The value of these terminal resistors is determined from the data transfer rate and cable
lengths. The terminal resistors are located in the control units.
If only one control unit is connected to a bus driver (e.g. SZL to the bus driver BD0), the
connections on the bus driver and on the control unit are fitted with a terminal resistor.
Terminalresistor
This type of connection at the central gateway module is called "end node termination".
If the connection at the control unit is not the physical finish node (e.g. DSC, ICM and
DME at the bus driver BD2), it is referred to as a FlexRay transmission and forwarding
line. In this case, both components must be terminated at the ends of each bus path
with terminal resistors.
Through-loopedFlexRay
This connection option exists for the central gateway module and a number of control
units. However, the control unit with a transmission and forwarding line has a 'non-end
node termination' for data pickup. This type of termination cannot be tested using measurement systems at the control unit connector due to its resistor / capacitor circuit.
To measure the (current-free) FlexRay bus to determine the line or terminating resistance,
please be sure to use the vehicle wiring diagram.
37
Bus Systems
TransmissionMedium-SignalProperties
The bus signal of the FlexRay must be within defined limits. A good and bad image of
the bus signal is depicted below. The electrical signal must not enter the inner area
neither on the time axis nor on the voltage axis. The FlexRay bus system is a bus system
with a high data transmission rate and therefore with rapid changes in the voltage level.
The voltage level as well as the rise and drop of the voltage (edge steepness) are
precisely defined and must be within certain values. There must be no infringements of
the marked "fields" (green and red hexagon).
Electrical faults resulting from incorrect cable installation, contact resistance etc. can
cause data transmission problems.
Index
Explanation
Index
Explanation
Good image
Bad image
The images shown above can be depicted only with very fast oscilloscopes.
The oscilloscope in the BMW diagnostic system is not suitable for representing such
images.
38
Bus Systems
The voltage ranges of the FlexRay bus system are:

System ON - no bus communication 2.5 V
High signal - 3.1 V (voltage signal rises by 600 mV)
Low signal - 1.9 V (voltage signal falls by 600 mV)
The voltage values are measured with respect to ground.
ScopesettingstotesttheFlexRay:
CH1: Test probe 1, range 1 V/Div; DC coupling

CH2: Test probe 2, range 1 V/Div; DC coupling
Time: 5 S/div
Workshop Hint
As of ISTA v2.24.2 the RECORD button becomes
unavailable if the Time/Div is < 2ms, however if you
press the HOLD button and then press it again, the
RECORD button becomes available for a short period
of time.
39
Bus Systems
DeterministicDataTransmission
The CAN-Bus system is an event-controlled bus system. Data are transmitted when an
event occurs. In the event of an accumulation of events, delays may occur before further
information can be sent. If an item of information cannot be sent successfully and free of
errors, this information is continually sent until the communication partner confirms its
receipt.
If faults occur in the bus system, this event controlled information can back up causing
the bus system to overload, i.e. there is a significant delay in the transmission of individual
signals. This can result in poor control characteristics of individual systems.
The FlexRay bus system is a time-controlled bus system that additionally provides the
option of transmitting sections of the data transmission event-controlled. In the time
controlled part, time slots are assigned to certain items of information. One time slot is
a defined period of time that is kept free for a specific item of information (e.g. engine
speed).
Consequently, important periodic information is transmitted at a fixed time interval
in the FlexRay bus system so that the system cannot be overloaded.
Other less time-critical messages are transmitted in the event-controlled part.
An example of deterministic data transmission is outlined in the following.
40
Bus Systems
Index
Explanation
Time-controlled part of cyclic data transmission
Event-controlled part of cyclic data transmission
Cycle (5 ms total cycle length of which 3 ms static

(= time-controlled) and 2 ms dynamic (= event-controlled)
Engine speed
<
Angle
Temperature
Road speed
xyz..abc..
Event-controlled information
Time
BusProtocol
Deterministic data transmission ensures that each message in the time-controlled part is
transmitted in real time. Real time means that the transmission takes place within a
defined time.
Therefore, important bus messages are not sent too late due to overloading of the bus
system. If lost due to a temporary problem in the bus system (e.g. EMC problem) a
message cannot be sent again. A current value is sent in the next assigned time slot.
HighBandwidth
The FlexRay bus system operates with a data transmission rate of 10 Mbits/s.
This speed corresponds to 20 times the data transmission rate of the PT-CAN.
Synchronization
A common time base is necessary in order to ensure synchronous execution of individual

functions in interconnected control units. Time matching must take place via the bus
system as all control units operate with their own clock generator.
The control units measure the time of certain synchronization bits, calculate the mean
value and adapt their bus clock to this value. This system ensures that even minimal time
differences do not cause transmission errors in the long term.
41
Bus Systems
Ethernet-FasterProgrammingAccess
EthernetinF0xVehicles
Ethernet is a manufacturer-neutral, cable-bound network technology. Most computer
networks nowadays are based on this data transfer technology.
The so-called Ethernet was developed more than 30 years ago. Since then, the data
transfer rates have multiplied. The IEEE 802.3u specification with 100 MBit/s data transfer rate is used in F0x vehicles. The IEEE 802.3xx is a standard for cable-bound networks of the Institute of Electrical and Electronic Engineers. This specification is also
known as "Fast Ethernet".
The transfer protocols are the protocols TCP/IP (Transmission Control Protocol/ Internet
Protocol) and UDP (User Datagram Protocol).
Application
The Ethernet in the diagnosis socket is only enabled when the BMW programming
system (ICOM A) is connected. There is an activation bridge in the programming
connector, between pins 8 and 16. This switches the power supply for the Ethernet
controller in the central gateway module.
This means that Ethernet access to the central gateway module is disabled while the
vehicle is being driven by the customer. The Ethernet connection between the information and communications systems is permanently enabled in the diagnosis socket independently of the activation bridge.
Security
Each participant in an Ethernet has an individually assigned identification number, an

MAC address (Media Access Control). This address and the VIN (Vehicle Identification
Number) identifies the vehicle to the BMW programming system on connection setup.
This prevents changes to the data records and stored values by third parties.
In the same way as in a computer network in the office, each device in a network must
receive unique identification. This is why the central gateway module is assigned a socalled IP address by the programming system after connection setup.
The function of an IP address in a network corresponds to that of a telephone number in
the telephone network. This IP address is assigned per DHCP (Dynamic Host
Configuration Protocol). This is a method of automatic allocation for IP addresses to user
devices in a network.
42
Bus Systems
FeaturesofEthernet
Very high data rate of 100 MBit/s.

System start time with connection setup and address
assignment under three seconds, sleeping under one second.
System access only via BMW programming systems.
FunctionsofEthernet
Faster programming of the vehicle in Service.

Ethernet
Ethernet
ZGM
OBD2
CIC
Index
Explanation
Index
Explanation
ZGM
OBD2
Diagnosis socket
CIC
Central information computer
The wiring between the diagnosis socket and ZGM is with two pairs of wires without
additional shielding. There is also an activating line that supplies the Ethernet controllers
in the control units with voltage.
There is a Cat5 cable between the diagnosis connector and the BMW programming system. These Cat5 cables are network cables with four twisted, unshielded pairs of wires
that are approved for signal transfers at up to 100 MHz operating frequency. However,
two pairs of wires are sufficient for the transfer capacity required in the F01/F02.
43
Bus Systems
FiberOpticBusNetworks
The ever-increasing level of features available in todays automobiles require a corresponding increase in vehicle electronic systems. The transmission of data, voice and
images require an efficient method to move data.
Copper wire bus networks offer many advantages. However high data transmission rates
in copper wires can cause electro-magnetic interference with other vehicle systems.
Compared with copper wires, fiber optic lines require less space and are lighter in weight
for the same transmission band width. In contrast with copper wires, which carry digital or
analog voltage signals as the means of transmitting data, fiber optic busses transmit light
pulses.
Fiber Optic technology has been in use in the telecommunications industry for many
years. However, this type of fiber-optic cable is not practical for automotive use. These
cable utilize glass based fibers which are not practical for automotive use. They are subject to fracture from vibration and do not hold up to tight radius installations.
POF (polymer optical fibers) were developed for the automotive industry. These fibers
were developed and manufactured by Dow-Corning.
The most commonly used fiber optics conductors are:
Plastic fiber optics conductors
Glass fiber optics conductors
Only plastic fiber optics conductors are used in BMW vehicles.
There are significant advantage to using POF fiber optic cables:
There is a low sensitivity to dust. Small amounts of contamination do not adversely
affect communication.
They are easy to work with. These fibers can be bent to a radius of approximately
50mm. This allows for practical installation within the vehicle.
Processing is practical, these fibers can be cut and modified which makes the production of wiring looms easy. Service repairs are also made simple.
These fibers are inexpensive to manufacture and do not require expensive connections or housings.
Fiber optic cables are imperious to EMF (Electromotive Interference).
44
Bus Systems
Design
A fiber optics conductor is a thin cylindrical fiber made of plastic which is enclosed by a
thin sheathing or jacketing. The actual fiber optics conductor is embedded in the sheathing material that serves the purpose of protecting the actual fibers.
Structureofafiberopticsconductor
Index
Explanation
Fiber Core
Sheathing
Padding
PrincipleofOpticalTransmission
In principle, any system that transmits electrical signals with the aid of light beams (luminous radiation) consists of the components shown in the following illustration. The signal
controls a light (radiation) source such that the radiation intensity of this source is proportional to the time fluctuations of the signals.
Parallels can be drawn when comparing an optical message system with a modem transmission system (computer - internet):
Index
Explanation
Index
Explanation
Optical transmission
Photodiode
(Receiver)
Electrical transmission
Receiver
Source
Demodulator
(Receiver in modem)
Light-emitting diode
(Transmit diode)
Cable
Headrest guide
Modulator
(Transmitter in modem)
45
Bus Systems
The fiber optics conductor assumes the function of the transmission channel. The fiber
optics conductor is particularly insensitive to external electromagnetic influences.
Comparison of an optical message transmission system with a conventional message
system.
Modemtransmission:
As part of modem transmission, the modulator, the transmit part of the modem, converts
the digital signals into analog signals. The analog signals are transmitted via the telephone network to the next computer.
The demodulator, the receive part of the modem, at this computer converts the analog
signals back to digital signals.
Opticaltransmission:
With optical message transmission, on the other hand, the digital signals are converted
into optical signals by means of a light emitting diode (LED).
The optical signals are transmitted via fiber optics conductors to the next control unit.
The photodiode at this control unit converts the optical signals back to digital signals.
PrincipleofLightTransmission
The electrical signal generated by the control unit is converted to an optical signal by an
internal transmitter module and sent along the fiber optic bus. The fiber core carries the
light beam to a receiver module which converts the light signal back to a useable electrical signal.
The light therefore passes through the fiber optics conductor. The light is then converted
back to an electrical signal with the aid of a receiver component.
Principleofdatatransmissionwithlight
46
Bus Systems
Index
Explanation
Transmit diode
Sheathing
Fiber core
Receive diode
LightAttenuation
Attenuation refers to the reduction in strength of a signal. Light transmitted along the
optical fiber becomes weaker the further it has to travel.This effect is known as attenuation. This attenuation is comparable to the electrical resistance of a copper wire.
Attenuation is usually measured in decibel units (dB). In fiber optic cables, attenuation is
measured in terms of the number of decibels per unit of length (foot/meter etc). The less
attenuation per unit distance, the more efficient the cable.
Index
Explanation
Transmit diode
Sheathing
Fiber core
Receive diode
Attenuationofthelightwithinafiberopticsconductor
In comparison with an electrical circuit, think of attenuation as light resistance. The

more attenuation in the fiber optic cable, the less light output to the receiver module.
The average attenuation for fiber optic bus lines is .5 decibels (dB) for each connector
and .3 dB for each meter of cable.
CausesofExcessiveAttenuation
Excessive attenuation can be caused by the following reasons:

Bends in the fiber optic cable with a radius of less than 50mm.
Kinks in the fiber optic cable
Squashed or compressed fiber optic cable
Damaged insulation on fiber optic cable
Stretched fiber optic cable
Dirt or grease on the exposed cable ends
Scratches on the exposed cable ends
Overheated fiber optic cable
47
Bus Systems
Here are some examples of various fiber optic cable failures:
Bending Radius
Kinking
The plastic fiber optic cable should not be bent to a

radius of less than 50mm.
Fiber optic cables must not under any circumstances be kinked when fitted because this damages the cladding and the fiber core. The light is
partially dispersed at the point where the fiber is
kinked and transmission loss results.
That is roughly equivalent to the diameter of a softdrink can. Bending the cable any tighter can impair
its function or irreparably damage the cable.
Light can escape at points where the cable is bent
too tightly. This is caused by the fact that the light
beam strikes the interface between the core and
cladding at too steep an angle and is not reflected.
Even just kinking the cable once very briefly is

enough to cause permanent damage.
Compression Points
Stretching
Compression points must also be avoided because

they can permanently deform the light conducting
cross section of the optical fiber. This would cause
a loss of light.
Overstretching of the fiber optic cables, caused by

pulling for example, can destroy them.
48
Bus Systems
Stretching reduces the cross-sectional area of the

fiber core. Restricted passage of light is the end
result.
Abrasion Points
Dirty or Scratched Fiber Optic Cable Ends
In comparison with copper wires, abrasion of fiber

optic cables does not cause a short circuit.
Another potential source of problems is dirty or

scratched cable ends. Although the ends of the
cables are protected against accidental contact,
damage can still occur by incorrect handling.
Instead, loss of external light occurs.

The system then suffers interference or fails completely.
Dirt on the end of an optical fiber will prevent light

from exiting/entering. The dirt absorbs the light and
increases attenuation.
ServiceConsiderations
Two optical bus systems for data transmission have been developed for BMW vehicles:
MOST and byteflight.
The light length is 650 nm (red light).
Three different colors are used to differentiate between the fiber optics conductors for
the different bus systems:
Yellow: byteflight
Green: MOST
Orange: Service repair line
During repair work, there are some things that need to be taken into account when working with fiber optic cables. Any paintwork which requires the use of drying by heat, the
temperature should not exceed 85C. This could case deformation of the fiber optic
cable resulting in excessive attenuation.
Extreme care should be taken around fiber optic cables. Any wiring harness that contain
fiber optic cables should not be subjecting to stretching, pulling or any undue stress.
49
Bus Systems
CableRepair
Repair cable are available for the fiber optics. The MOST bus which is normally green in
the vehicle is repair using a black or orange cable. The MOST bus allows for up to one
splice between control units.
Special crimping pliers are used to fit the sleeves correctly on the fiber optics conductors.
The exact procedure is described in the operating instructions for the crimping pliers.
The byteflight which is a safety critical network does not allow for any splices or repairs
between control units. The entire defective optical cable must be replaced.
Replacement cables are orange or black.
Thefiberopticsconductorsinthebyteflight systemcanNOTbe
repaired.IncontrasttotheMOSTbuswhichalowsone(1)splice
betweencontrollers(whenusingtheproperpart#)adefective
byteflight cablebetweencontrollersMUSTbecompletelyreplaced.
FiberOpticConnectors
There are slight differences between the connectors on the MOST and byteflight bus.
The transmitter/receiver module on the MOST bus are set back into the control unit
housing. This setup allows for the protection of the delicate fiber ends of the cable. Also,
MOST cable connectors are marked 1 and 2. 1 is assigned to the incoming optical fiber
and 2 is assigned to the outgoing optical fiber (see connection of control units for more
information).
Note:RefertotheMOSTBusDiagnosissectioninthistrainingmaterialfor
moreinformation.
50
Bus Systems
MOST
MOST is a communications technology for multimedia applications that was specially
developed for use in motor vehicles.
MOST stands for Media Oriented System Transport. The MOST bus is designed
as an optical ring and uses light pulses for transmitting data.
MOST technology satisfies two important requirements:
1. The MOST bus can transfer control, audio and navigation data.
2. The MOST technology makes available a logic frame model for
controlling the great variety and complexity of the data.
Multimedia components such as:
Telephone
Radio
E90MOST
Television
Navigation system
CD changer
Amplifier
Multi-information display/on-board monitor
The new logic interconnection and networking of the
components gives rise to an enormous increase in
system complexity. Since this new dimension of system complexity can no longer be managed with the
familiar bus systems, a new bus technology is
required: MOST.
The MOST bus is designed as a ring structure and
uses light pulses for transmitting data. Data transmission takes place only in one direction. Fiber optics
conductors are used as the data transmission medium.
51
Bus Systems
MOSTDesign
The MOST bus is designed as a ring structure and uses light pulses for transmitting data.
Data transmission takes place only in one direction.
MOST combines the individual components to form one central unit.
As a result, the components interact to a greater extent. The plug&play principle enables
simple system expansion with individual components.
MOST is capable of controlling function that are distributed in the vehicle and to manage
them dynamically.
An important feature of a multimedia network is that it not only transports control data
and sensor data.
Features
High data rates: 22.5 MBits/s
Synchronous/asynchronous data transmission
MOST assigns the control units nodes in the bus
Fiber optics conductors as data transmission medium
Ring structure
The MOST not only represents a network in the conventional sense but it also provides
integrated technology for multimedia and network control.
Ringstructureofanetwork
52
Bus Systems
Index
Explanation
Transmitter (Pin 1)
Receiver (Pin 2)
RingStructure
Each terminal device (node, control unit) in a network with a ring structure is connected
by means of a cable ring.
A message indicating that transmission is possible circulates on the ring. This message is
read and passed on by each node (control unit).
When a node wishes to send data, it changes the ready-to-send message to an "occupied" message. It then adds the address of the receiver, an error handling code and the
data.
To ensure the signal strength is retained, the node, through which the data package
passes through, generates the data once again (repeater).
The node that is addressed as the receiver copies the data and forwards them in the circuit. If the data reach the transmitter again, it removes the data from the ring and resets
the ready-to-transmit message.
Specifically: The physical light direction runs from the master control unit (e.g. multi-audio
system controller) to the fiber optics conductor connector and from here to the control
units (e.g. CD-changer in the luggage compartment). The light then returns from the last
control unit back via the flash connector to the master.
Advantages:
Distributed control
Large network expansion
Disadvantages:
Intricate troubleshooting
Malfunctions cause network failure
Intricate and extensive wiring
Each MOST control unit can send data on the MOST bus. Only the master control unit
can initiate data exchange between the MOST bus and other bus systems.
In order to meet the various requirements of the different data transmission applications,
each MOST message is divided into 3 parts:
Control data: e.g. light intensity (luminosity) control
Asynchronous data: e.g. navigation system, vector representation
Synchronous data: e.g. audio and video signals
53
Bus Systems
The MOST bus has a ring structure. The various channels (synchronous channel, asynchronous channel and control channel) are transmitted synchronously on a medium. The
data are available in the entire ring, i.e. the data are read non-destructively (copied) and
can therefore be used by the various components.
The structure of the MOST bus enables easy expansion of the system with further components. The installation location of the components in the ring depends on the specific
function. There is no need to operate a reserve for future systems (e.g. double coil speakers).
The receiver and transmitter are connected with each other in the event of a component
failing. The ring therefore remains operative. The receiver and transmitter are separated
only if one control unit is supplied with power. These two units are completely operative
together with the transmit and receive system.
NetService disassembles the data packages in individual parts and reassembles them.
The receiver and transmitter are a BMW development in co-operation with Infineon and
Oasis. The information is transmitted by light pulses with a wave length of 650 nm (visible
red light). No laser but rather an LED is used to generate the light. The bus can be woken
optically, i.e. an additional wake-up line is not required. The power intake in sleep mode is
very low.
DatatransmissionontheMOST-bus
54
Bus Systems
Index
Explanation
Synchronous data
Asynchronous data
Control data
Connection of Control Units

The connection between the individual control units is provided by a ring bus that transports the data only in one direction. This means that a control unit always has two fiber
optics conductors, i.e. one for the transmitter and one for the receiver.
A pure fiber coupling is used in MOST control units. In this way, together with the fibers in
the control unit, the transmit and receive diodes can be positioned at any point in the
control unit. As a result, the fiber areas can be set back in the wiring harness connector,
thus rendering additional protection for the sensitive end faces unnecessary.
The 2-pole fiber optics conductor module is identical for all types of connector. The parts
family and contact parts have been declared as the standard within the MOST cooperation.
Index
Explanation
Fiber optic connector
Control unit socket
Fiber optic jumper
Receiver module with diode
Connector for fiber optics conductor
Index
Explanation
Pin 2
Pin 1
Pin 1 is always designated for the incoming fiber optics conductor

and pin 2 for the transfer fiber optics conductor.
55
Bus Systems
FiberOpticConnector
The use of the fiber optic connector provides the advantage of being able to easily retrofit
control units in the area of the luggage compartment.
Fiberopticcableconnector,rearleftintheluggagecompartment
The fiber optic cable connector is located in the luggage compartment of the F01/F02, to
the left behind the side wall trim. The fiber optic cable connector is arranged in the
MOST bus system between the front area of the vehicle (head unit, DVD changer) and
the rear area of the vehicle (TCU, VM etc.).
One or two fiber optic connectors are installed corresponding to the equipment configuration. One fiber optic connector is responsible for the factory-installed control units. The
other fiber optic connector is used for the preparations for options.
The ends of the fiber optic cables, for additional options, are always grouped together on
the same row in the fiber optic connector to avoid damage to the ends of the fiber optic
cables.
As soon as the retrofit is installed, the fiber optic connectors are reconnected according
to instructions and integrated in the MOST bus. Within the framework of programming,
the control unit sequence is reloaded into the master control unit.
56
Bus Systems
MOSTControlUnitsandLightDirection
In F0x vehicles the MOST bus is used for the components in information/communication
systems. The Car Information Computer (CIC) is used as the master control unit. Other
bus users may be:
DVD changer
Instrument cluster
Top-HiFi amplifier
Satellite tuner SDARS (on early CIC cars)
TCU/Combox
Rear Seat Entertainment
ULF-SBX high
TheMOSTprogrammingaccessusedinBN2000modelsisnolonger
requiredforBN2020F0xvehicles.Theprogrammingonthesevehicles
isdoneviatheEthernetaccesspoint.
LightDirection
Data are always sent in one direction on the MOST bus. Each control unit can send data
on the MOST bus.
The physical light direction runs from the master control unit (Car Information Computer)
to the DVD changer, to the instrument cluster, to the central gateway module and from
there to the fiber optic cable distributor. All the control units fitted in the rear end are connected at the fiber optic cable distributor. From the last control unit, the light returns to
the master control unit.
57
Bus Systems
MOSTringintheF01/F02
KOMBI
DVDC
CIC
SDARS
ZGM
RSE
TCU
TOP HIFI
ULF SBX
Index
Explanation
Index
Explanation
TOP HIFI
Top-HiFi Amplifier
KOMBI
Instrument Cluster
DVDC
DVD Changer
SDARS
Satellite Tuner
RSE
Rear Seat Entertainment
ULF-SBX
Interface Box
TCU
Telematics Control Unit
ZGM
Central Gateway Module
CIC
Car Information Computer
RegistrationofcontrolunitsintheMOST
Precisely in the same way as on the E6x models, the control units installed on the MOST
bus are stored in a registration file in the master control unit. The corresponding data are
stored during the production process and, in connection with control unit retrofits, after
programming the respective control unit.
The control units and their order on the MOST bus are stored in this registration file. With
the fiber optic cable connector, it is possible to connect control units in the rear area of
the vehicle ex factory or after a repair in different order. With the aid of the registration file,
the BMW diagnosis system can determine the installed control units and their order.
In addition, this registration file is also stored in the central gateway module so that there
is still access to the control unit registration in the event of a fault in the MOST framework. This means that the diagnosis can be used to call up the last functional status from
the central gateway module.
Although the master control unit of the MOST, the CIC, is connected to the K-CAN, it
does not carry out the function of a gateway control unit. If communication on the MOST
is no longer possible, the necessary data can only be read out via the central gateway
module.
58
Bus Systems
Bandwidths
The bandwidth indicates the capacity of the network, i.e. how many data items can be
transmitted simultaneously.
The bandwidth differs considerably in the various applications.
The aim is that all vehicle occupants will be able to call up different services simultaneously, e.g.
The driver calls up navigation information
The front passenger listens to the radio
A rear passenger listens to a CD
The other rear passenger watches a DVD
Application
Bandwidth
Dataformat
AM-FM
1.4 Mbit/s
Synchronous
MC
1.4 Mbit/s
Synchronous
CD
1.4 Mbit/s
Synchronous
MD
1.4 Mbit/s
Synchronous
Telephone
1.4 Mbit/s
Synchronous
SBS
1.4 Mbit/s
Synchronous
VCD
1.4 Mbit/s
Synchronous
DVD
2.8 - 11 Mbit/s
Synchronous/asynchronous
Navigation
250 kbits/s
Asynchronous
Telematics service
Various
Synchronous
The data transmission rate of 1.4 Mbits/s for audio data is derived from a scanning frequency of 44.1 kHz per channel (two channels for stereo) and a resolution of 16 bit.
The bandwidth of the MOST of 22.5 MBits/s is used in time multiplex by synchronous
channels, asynchronous channels and control channels. The division in synchronous and
asynchronous channels takes place to suit requirements.
Channels for control information have a smaller bandwidth of 700 kbits/s. This corresponds to approximately 2700 telegrams per second. At present there is no device that
can accept and process even a third of this number of telegrams per second.
In future, the MOST will be equipped with a data transmission rate of 50-150 MBits/s.
59
Bus Systems
MOSTBusDiagnosis
Due to the differences in the configuration of the MOST bus, diagnosis methods will differ between models. However, there are many similarities and there are some basic rules
which apply to all MOST equipped vehicles.
It is important to remember that on the MOST network, messages can only be transmitted provided the bus ring is complete and fully functional. If there is a ring fault in the
MOST network, the diagnostic system only communicates with the instrument cluster
and the Control Display because both of these modules are directly connected to the
K-CAN System Bus.
The fiber optic signals on the MOST network always travel in one direction and only in
one direction. Signals always originate at the Control Display or the CIC (depending on
the model) and travel in and out of all the modules in the ring and back to the Control
Display or CIC.
The MOST bus allows intersystem fault memory entries in the individual control modules.
A feature of the system faults is that faults may be entered in a control module although
the control module is OK. Conclusions may be drawn about the cause of the fault, using
the fault information stored in all the control modules.
The possible system faults are:
Optical wave guide communication fault
A Control Module does not switch a light off (All MOST Control Modules)
Network wake-up unsuccessful
Ring fault diagnosis run
OpticalWaveGuideCommunicationFault
This fault indicates a problem with optical transmission. Insufficient light is being received
by one of the modules in the ring. The loss of light may be caused by:
Defective optical wave guide, Harness twisted too tightly (Min. bend radius 50mm.)
Light output or reception sensitivity of a diode is too low
Connector not installed correctly
Voltage fluctuation while powering up a control module
If the fault is stored, the system triggers a reset and starts up again. The music is
switched off briefly and the display screen of the Control Display continues to operate.
To find the module responsible for the fault, the fault memory of the modules must be
read in MOST ring order.
60
Bus Systems
Fault lies between the module with the fault code (B) and the preceding module (A).
If the voltage has dipped below 9v, the fault may be incorrectly stored. If the voltage is low
perform the following test after connecting a battery charger.
1. Clear the fault memory in control module B.
2. Lower the light output in control module A.
3. Read out the fault memory in the MOST ring in order.
4. If control module B is again the first to store the fault, it can be assumed the fault lies
between control modules A and B.
Then, check control modules A and B for loose connections and check the optical wave
guide for kinks. If the visual inspection is OK, the fault can be located using the OPPS
tester on older vehicles or optionally performing the following tests.
Remove the input optical wave guide from control module B and confirm the presence of light. If light is present, install by-pass optical wave guide in place of control
module A, clear fault codes in module B and perform ring break test. If MOST network operates properly, then control module A is at fault and must be replaced. If
MOST network still has a fault, put module A back in the network and by-pass module B. Clear faults and again perform ring break test. If MOST network operates now
problem is with control module B and it must be replaced.
If light is not present at input of module B, perform by-pass of module A as above.
The possible fault scenarios are:
Transmit diode in module A defective
Receive diode in module B defective
Optical wave guide fault between modules A and B
Software error or fault in module A or B
ControlModuleDoesNotSwitchOffLight
When the MOST network is requested to sleep, the Control Display switches off the light
in the MOST ring. The lack of light input is a signal to the individual control modules to
switch off their light output and enter sleep mode.
If a control module does not switch off its light, all down stream control modules register
the fault A Control Module is not switching light off.
61
Bus Systems
Failureofacontrolmoduletoturnitslightoff,willcausetheMOST
networkNOTtoentersleepmode.IftheMOSTnetworkfailstosleep,
therestofthecarwillnotbeabletoentersleepmode.Thiswillleadto
batterydischarge.
To diagnose, read out fault memory in MOST ring order.
The fault lies in the control module that precedes the module where the fault is first
stored.
Always confirm the problem by first clearing the fault and performing the diagnosis a second time. If the same results occur, replace the defective control module.
NetworkWakeupUnsuccessful
This fault indicates a problem with the optical transmission. An insufficient volume of light
is coming through one position of the ring and may be caused by:
Control Module is receiving no voltage
Optical Wave Guide harness defective
Optical Element in a control module defective (transmit or receive)
Connector not installed correctly
A distinction must be made as to whether the fault is currently present or sporadic.
For faults currently present, run the Ring Break Diagnosis Test Plan.
For sporadic faults perform the Luminous Power Reduction Test Plan.
RingBreakDiagnosis
Reading out the fault memory of the Control Display (Gateway) after performing the Ring
Fault Diagnostic, results in a fault of Ring Fault Diagnosis Carried Out being stored.
This fault memory is not a true fault memory entry, but only an output of additional information for relative node position.
62
Bus Systems
LightOutputReduction
Reducingthelightoutputofindividualcontrolmodulesisaconvenientmethodof
determiningtheareaofadefect.
Switch on the radio.

In Control Module functions, begin to activate luminous power reduction in the individual control module (In this test the light output of the selected control module is
reduced for 5 seconds and then automatically reset to normal output).
If the optical transmission for control module A to the next control module in the ring
(control module B) is OK, a slight noise may occur when the light output is reduced,
however the radio will continue to play.
If the radio goes off and comes back on again(radio volume may be reduced) in 5 to
10 seconds, the optical transmission between control modules A and B is defective.
If the visual inspection is OK, the fault can be located using the OPPS tester or
optionally performing the following tests.
Remove the input optical wave guide from control module B and confirm the presence of light.
If light is present, install by-pass optical wave guide in place of control module A,
clear fault codes in module B. If MOST network operates properly, then control module A is at fault and must be replaced.
If MOST network still has a fault, put module A back in the network and by-pass
module B. Clear faults.
If MOST network operates now problem is with control module B and it must be
replaced.
If light is not present at input of module B, perform ring break diagnostics.
RingBreakTest
If there is a break in the ring (a defect between two control modules) the following fault
patterns may occur:
Transmit diode of the transmitting control module defective
Power supply of the transmitting control module defective
Internal control module fault of the transmitting control module
Receiver diode of the receiving control module defective
Power supply of the receiving control module defective
Internal control module fault of the receiving control module
Optical wave guide between transmitting and receiving control module defective
63
Bus Systems
These faults may occur alone or in combination. To diagnose a ring break, the first step is
to locate the two control modules between which the transmission failure has occurred.
This is accomplished with the ring break diagnostic function. Once the two control modules have been identified and the diagnostics have been performed, remember to check
the power supply and ground circuit of both modules before condemning a module.
PerformRingBreakTest
The ring break test mode is entered automatically when the power to all the modules in
the MOST network is switched off and then switched back on. The most effective
method of switching the power off and on is to disconnect the battery negative terminal
for 45 seconds. This time will allow the capacitors of all the control modules to dissipate.
When the battery is reconnected the control modules wake up and in MOST network
order transmit a light signal to the next module. Each module checks to see if it has
received a light signal from the previous module. If the control module does NOT receive
a light input signal it still transmits a signal to the next module. A relative node number of
0 is stored in the control module that did not receive a signal but that transmitted one.
The MOST master control unit receives the light signal back and identifies which modules responded.
Go to Control Unit Functions Control Display Gateway and read fault memory.
The MOST master control unit will display a relative node number. This number will indicate how many modules communicated after the module which set the relative node
number of 0.
To find the control module with the relative node number of 0, count from the input side
of the MOST master(counting the MOST master as 0) towards the control modules.
When arriving at the control module with the number as displayed as the relative node
number, the last known communicating module has been found.
Example:
While performing the ring break diagnostics on an E65 the Control Display has set a relative node number of 2. Count the Control Display a 0, the Kombi will be 1 and the ASK
will be 2.
The ring break occurs between the ASK and the module which precedes it, the telephone module.
Whencountingcontrolmodules,themultimediachanger(ifequipped)
andtheNavsystemmustbecountedastwocontrolmodules.
Note:Moredetailsontheringfaultdiagnosiscanbefoundinthefunctional
descriptionMOSTbus:ringfaultdiagnosiscompletevehicle->Body->
Busfunctions->MOSTfunctions->Ringfaultdiagnosis.
64
Bus Systems
StatusWakeup
MOST control modules require high current during standby operation and must be disconnected or put in sleep mode to prevent the vehicle battery from being discharged. In
case of a fault on the MOST network that continuously wakes up, the entire MOST bus
will be woken up. The Control Display will wake up the CAN Bus and all the vehicle
busses will be woken up. This will lead to battery discharge.
It is of great benefit to know which module initiated the wake up call. In order to find out
which MOST node woke up the MOST bus, the following procedure is performed - In
Control Unit Functions, press STATUSWAKEUP
Three different response are possible:
Control Module woke up
Control Module woken up
Control Module not initialized
The Control Module with the status Control Module woke up is the module that woke
up the rest of the MOST bus.
This diagnosis only informs which control module woke, not the reason for the wake up,
diagnostic testing should be performed on the control module and related equipment.
FormoreinformationrefertothefollowingFUBs:
FUB-FPA-CHA1003FP-656582005Faultprofiles,MOST
FUB-DAA0302FB-656582004MOSTbus:Ringfaultdiagnosis
FUB-BLB0704FB-657761055MOSTbus:Ringfaultdiagnosis
FUB-DAA0701FB-656582003MOSTbus
FUB-DAA0302FB-656582005MOSTbus:statuswake-up
65
Bus Systems
Sub-busSystems
Sub-busses are also used in addition to the main bus systems. Sub-bus systems are
subordinate serial bus systems.
The most important sub-bus systems are outlined below:
K-Bus
LIN-Bus (Local Interconnect Network Bus)
BSD (Bit-Serial Data Interface)
Datarates
Mainbussystem
Datarate
Busstructure
K-Bus
9.6 kbits/s
Linear - one-wire
BSD
9.6 kbits/s
Linear - one-wire
LIN-Bus
9.6-19.2 kbits/s
Linear - one-wire
LoCAN
500 kBits/s
Linear, two wire
K-Bus
The K-Bus is a bidirectional one-wire interface. This means the K-Bus has only one single line for data transmission. Bi-directional means that the data are transmitted in both
directions.
The term "K-Bus (protocol)" is used for a series of sub-bus systems in the bus overview.
These sub-bus systems are used for various purposes. The K-Bus protocol used here is
a common component already used in predecessor models. The protocol is used in F0x
vehicles, e.g. on the following systems:
Connection between ACSM and TCU
Comfort Access
CAS-Bus
Consequently, it is possible to only transmit or receive at any one time. The data transmission rate of the K-Bus is 9.6 kbits/s.
The voltage level is between 0 V and 12 V when a message is sent on the K-Bus.
The voltage level changing from 0 V to 12 V corresponds to logic 1.
Logic 0 is when the voltage changes from 12 V to 0 V.
66
Bus Systems
K-BusintheE90
VoltagelevelontheK-Bus
The K-Bus is used as a main bus or sub-bus system depending on the vehicle model.
LIN-Bus
The LIN-Bus was developed to provide a standard network for the automobile industry.
The LIN-Bus has been used as early as the
E60 and was also used to control the outside
mirrors on the E46. Mainly, the versions V2.0
or higher are used in F0x vehicles.
LIN-BusintheE90
Standardization saves costs in:

Development
Production
Vehicle servicing
The LIN-Bus system comprises the following
components:
Higher-ranking control unit (master)
Lower-ranking control units (secondary
control units)
One-wire line
A bidirectional one-wire bus line serves as the transmission medium for the LIN-Bus. The
bus protocol is divided strictly hierarchically in master and secondary control units. A maximum of one master is permitted for a LIN-Bus system.
67
Bus Systems
The data transmission rate of the LIN-Bus can be up to 19.2 kbits/s.

The following transmission speeds are possible:
2.4 kbits/s
9.6 kbits/s
19.2 kbits/s
The LIN-Bus is currently installed in the following systems:
Air conditioning (9.6 kbits/s)
Between the driver's door module and driver's door switch cluster (19.2 kbits/s)
Tire pressure control (9.6 kbits/s)
The LIN-Bus master forwards the requests of the control unit to the secondary control
units (lower-ranking or subordinate control units) in its system.
The LIN-Bus master controls and monitors the message traffic on the bus line.
The current messages are transmitted cyclically by the LIN-Bus master.
LIN-Bus secondary control units of the air conditioning system are:
Actuator motors for the air distribution flaps
Blower regulator
Electric auxiliary heater
The LIN-Bus secondary control units wait for commands from the LIN-Bus master and
communicate with it only on request.
A LIN-Bus secondary control units can send the wake-up sequence of its own accord in
order to end sleep mode.
The LIN-Bus secondary control units are installed in the users of the LIN-Bus system
(e.g. stepper motors for fan flap adjustment).
Due to the lower data rate on the LIN-Bus, terminal resistors are not used.
In F0x vehicles, the following control units still correspond to the V1.x specification:
Belt hand-over
Outside mirror
Blower output stages
Intelligent Battery Sensor
68
Bus Systems
LINV2.0(orV2.1)
LIN components that correspond to the specification of data protocol LIN V2.0 or higher
have extended functions.
The LIN components for V2.x are delivered with a device ID and a base configuration. The final (dynamic) configuration and the allocation of the ID number take place
on commissioning by the master control unit.
If one of these components is replaced, this operation must be initiated manually by
means of the BMW diagnosis system.
The data protocol has become more variable, permitting, if required, periodic alongside sporadic messages as of specification V2.0. These "sporadic frames" are only
sent if the master control unit requires data from the secondary control units or outputs data. Without such a request, the time slots in the messages remain empty.
The master control units can send so-called multiple requests to secondary control
unit groups. To reduce the bus load, the contacted secondary control units only
respond in the case of changed values (e.g. door contact). All master control units of
the LIN V2.x specification are downwardly compatible to (secondary control units)
components of previous specifications.
However, all V2.0 secondary control units also require a V2.x master controller.
A number of the connected components are only diagnosis-capable to a limited degree,
for example the rain-light-solar-condensation sensor.
In this case, the master control unit serves as the gateway to the remaining bus system.
The diagnosis requests from the ZGM or BMW diagnosis system are inserted in the sporadic section of a LIN frame.
A special feature introduced with BN2020 in the F01/F02 is that the data communication
between the Comfort Access and diversity antenna is implemented with 20.0 kBit/s due
to the large number of small data packages.
The slightly higher transfer rate means that the time slots in the data protocol can be better exploited. The master control unit sends the "sleep command" to place the LIN in the
idle state.
The "sleep command" can also be sent with terminal R "On", e.g. for mirror adjustment.
The "wake-up command" can also be sent by a secondary control unit.
The LIN messages in the data protocol are divided into four sections:
Synchronization
Identifier
Data
Checksum
69
Bus Systems
F0xvehicleLINBusoverview
70
Bus Systems
D-Bus
The diagnosis bus or D-Bus represents a
physically separate access facility to the outside. Interacting with the gateway (junction
box), it enables access to all data busses.
When a diagnosis unit is connected, on
request of the gateway, specific system information relating to the vehicle are made available via the diagnosis bus. A complete list of
control units installed in the vehicle is transferred together with the self-diagnosis information. The data transmission rate of the
D-Bus is 10.5 - 115 kbits/s.
D-BusinanearlyE90
D-CAN
In order for BMW to meet the requirements of standard ISO 15765 (Diagnostics on CAN
with KWP 2000 [Keyword Protocol 2000] or UDS [Unified Diagnostic Service]) D-CAN
(Diagnostics on Controller Area Network) replaced the D-Bus diagnostics interface worldwide.
This legal requirement in the USA mandates that all vehicles be equipped with the D-CAN as from model year
2008. BMW began the transitional phase in September
2006. The E70 was one of the first new vehicles equipped
with D-CAN and then the modification was phased-in on
all other BMW models.
The D-CAN data-signalling rate is 500 kbit/s.
The measured resistance between the wires should be
60 .
D-CANasfromE70
An OBD-tool or BMW diagnostics system is automatically detected and distinguished

during data output. The second TXD interface (pin 8) is not necessary.
The ICOM A provides the interfaces for connection to the vehicle OBD II female diagnostic interface connector. A powerful computer core enables it to work as a protocol converter to assume the data interchange between the tester and the vehicle control units as
well as the signal processing for connection of the measurement system (IMIB).
71
Bus Systems
Power is supplied by way of KL 30 across the vehicle interface. ICOM A is rated for a
minimum voltage of 8 V. Stable operation is only ensured if the power supply is above the
minimum voltage limit.
ICOM A can be connected to the workshop network by a
Ethernet LAN cable (wireless connection by WLAN will
be available in the near future). The maximum data rate is
100 Mbit/s. Or directly to the ISID on offline mode.
The communication with the MOST Bus (for programming) is supplied by ICOM B on BN2000 vehicles. For
this purpose ICOM B (2) is to be connected with the
ICOM A (1) by way of a supplied USB cable (3). The host
communication is thru either a workshop network LAN
connection (4) or WLAN.
Note:WithBN2020vehicles(F0x)diagnosisand
programmingisdonethroughISIDwith
ICOMAonly(programmingdonethrough
ethernetconnection).
OBD II access in all vehicles remains unchanged; The diagnosis socket is located under the dashboard on the driver's
side.
The pin assignments at the OBD II connector are as follows:
3, 11, 12, 13 = Ethernet connections. (F0x vehicles)
16 = Terminal 30
5 = Terminal 31
14 + 6 = Communication connections
8 = Activation of Ethernet
The diagnosis socket is located under the dashboard on the driver's side.
72
Bus Systems
Bit-serialDataInterface
The bit-serial data interface is used to connect the alternator and the intelligent battery
sensor to the digital motor electronics.
Overviewofbit-serialdatainterface
Index
Explanation
Alternator
Bit-serial data interface
Digital motor electronics
Intelligent battery sensor
Scopevoltagewhen
binary0is~12v
Scopevoltagewhen
binary1is~900mv
Local-CAN
The Local-CAN serves to transfer the high data volumes of the Short-range and long
range radar sensors to the ICM in F0x vehicles with.
The Local-CAN has a data transfer rate of 500 kBit/s and is designed as a twisted pair of
wires. The 2 (120 ) terminal resistors in the Local-CAN are located in the ICM and the
long range radar sensor which equal to a measured resistance between the wires of 60 .
CAN Low to ground: V min = 1.5 volts

and V max = 2.5 volts
CAN High to ground: V min = 2.5 volts
and V max = 3.5 volts
The Local-CAN is also used in Night Vision 2 (F0x) system for diagnosis, programming
and camera control.
The camera is programmed through the NVE control unit. The control unit receives the
programming data for the camera through PT-CAN. The control unit forwards this data to
the camera through the Local-CAN.
When measuring Local-CAN voltage, the Oscilloscope (IMIB) settings
should be the same as for the PT-CAN and K-CAN 2 (refer to these for
an sample of the Local-CAN scope pattern).
73
Bus Systems
Gateways
Data exchange between the bus systems Gateways serve the purpose of coupling different types of bus systems, i.e. gateways connect bus systems with different logic and
physical properties.
They therefore ensure data exchange despite the different transmission rates of the individual bus systems.
Exampleofagatewayconnection
Index
Explanation
Index
Explanation
Linear bus system (e.g. KCAN)
Ring-structure bus system (e.g. MOST)
Gateway (e.g. M-ASK)
A gateway performs a dual function:

To collect information from various different networks.
To send information to the correct network.
Transmission rates, data volume and priority stages of the individual messages are filtered in the gateway and buffered if necessary.
The gateway converts the messages to suit the respective bus system based on gateway rules and conversion tables.
The respective bus system is now served and the messages reach their target address.
If necessary, messages that are not so important remain in the gateway memory. These
remaining messages are then sent later.
74
Bus Systems
GatewayRulesBasedontheExampleofaTrainStation
Index
Explanation
Index
Explanation
GW-R
Gateway rules
Bus 2
Slow bus
GW-T
Gateway table
A -> B
Table example: Message from A to B
Train 1 with yellow message
B -> A
Table example: Message from B to A
Train 2 with red message
5 min
5-minute intervals
Gateway
1h
1-hour interval
Bus 1
Fast bus
The express train 1 arrives at the station in 5- minute intervals. This train has a message
(yellow) for the train with the steam locomotive. The message is transferred to the first
wagon of the train with the steam locomotive.
In the meantime, an express train 2 arrives with a message (red) for the train with the
steam locomotive. Since the steam locomotive has not yet departed, the second message is also transferred to the steam locomotive and attached after the first wagon. This
procedure is repeated until the train with the steam locomotive leaves the station after
one hour.
The messages are parked in the station when the train with the steam locomotive is fully
loaded. When available, a new train with a steam locomotive is loaded with these messages.
75
Bus Systems
NOTES
PAGE
76
Bus Systems

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Table of Contents

Revision Date: 09/11

Ethernet - Faster Programming Access . . . . . . . . . . . . . . . . . . . . . . . . . .42

After completion of this module you will be able to:

Digital representation involves the representation of constantly changing variables in

10.5 - 115 kbits/s

Linear - one-wire parallel

Linear - two-wire parallel

Linear - two-wire parallel

Linear - two-wire parallel

Linear - two-wire parallel

Linear - two-wire parallel

Linear - two-wire parallel

Linear - two-wire parallel

Star structure - fiber optics conductor

Ring structure - fiber optics conductor

Star- two wire

* Also known to as I-Bus in earlier models

K-CAN stands for Karosserie (body) Controller

Voltage level on the K-CAN:

The K-CAN is operated as a one-wire bus if:

Junction box electronics

Values of the terminating resistors on the K-CAN:

PT-CAN stands for Powertrain Controller Area Network.

Digital Motor Electronics

Electronic fuel pump control

Electronic transmission control

Gear selector lever

Real time capabilities, deterministic (strictly defined) and redundant

Conditional real time capabilities - sufficient for control systems

No real time capabilities

Junction box control unit

Vertical Dynamics management (VDM)

Ride height sensors, front

EDC satellites with vertical acceleration sensors and solenoid valves

Ride height sensors, rear

FlexRay bus system

The FlexRay bus system is designed as a two-wire, single-channel bus

There is a short circuit in this section of line.

This section of line is damaged

This section of line is OK and the satellite is connected

There is a break in the line or the satellite is not connected

The two plug connections contain the power supply of

FlexRay (green wire)

For resistance measurement in the FlexRay,

The FlexRay bus system can be integrated in various

All control units (SG1...SG3) in line-based

The transmitted differential signal is

The satellites (control units SG2...SG5) in

Vertical Dynamics Management (VDM)

EDS satellites, front left

EDS satellites, front right

EDS satellites, rear right

FlexRay bus system

EDS satellites, rear left

Active steering system

Digital Motor Electronics

Dynamic Stability Control

Electronic damper control, rear left satellite