BMW F48 - D-Can; Ethernet; Most

F48�General�Vehicle�Electronics
1.�Vehicle�Electrical�System
13
The�CAN�bus�system�is�an�event-controlled�bus�system.�Data�is�transmitted�when�an�event�occurs.
As�these�events�have�different�priorities�(e.g.�ambient�temperature�has�a�lower�priority�than�a�DSC
intervention,�for�example),�the�priorities�are�also�sent�in�the�bus�message.�The�message�with�the
higher�priority�is�sent�first.�As�the�control�unit�still�wants�to�send�the�message�which�has�the�lower
priority,�it�frequently�results�in�overloading�in�the�bus�systems.
The�FlexRay�works�with�so-called�"time�slots".�With�this�method�the�messages�are�sent�and�are�not
controlled�by�events,�but�each�control�unit�in�the�FlexRay�network�is�assigned�a�fixed�time�slot�in�which
it�sends�its�message�within�a�certain�period.�This�time�slot�is�synchronised�with�every�restart�of�the
data�bus.�The�control�units�which�synchronize�the�FlexRay�are�always�labelled�in�the�bus�diagram�with
a�"S"�(see�chapter�1.1).
The�FlexRay�can�also�be�synchronised�with�the�BMW�diagnosis�system�in�the�event�of�a�fault�and
corresponding�fault�code.
1.2.4.�D-CAN
The�D-CAN�for�the�vehicle�diagnosis�has�a�data�transfer�rate�of�500�kBit/s.
1.2.5.�Ethernet
The�Ethernet�access�is�used�for�programming�the�entire�vehicle.
In�a�F48�with�navigation�system�the�map�update�for�the�navigation�can�also�be�effected�using�the
Ethernet�interface.
1.2.6.�MOST
In�the�F48�the�Media�Oriented�System�Transport�(MOST)�bus�works�at�a�data�transfer�rate�of
22.5MBit/s.
1.3.�Sub-bus�systems
1.3.1.�Local�interconnect�network�bus
Different�data�rates�are�used�for�the�local�interconnect�network�bus�according�to�the�information
required.�The�data�transfer�rates�of�the�local�interconnect�network�bus�in�the�F48�range�from�19.2kBit/
s�to�20.0kBit/s.
Examples:
• 19.2�kBit/s�FLEL,�FLER
• 20.0�kBit/s�remote�control�receiver
The�Body�Domain�Controller�is�designed�for�the�different�data�rates�at�the�corresponding�inputs.