GF00.19-P-0001R Extended Vehicle Networking (EVN), Function

GF00.19-P-0001R Extended Vehicle Networking (EVN), Function
- MODEL 230 up to 31.5.04
- Except CODE (494) USA version
- Except CODE (498) Japan version
- MODEL 230 up to 30.6.04
- With CODE (494) USA version
- Except CODE (498) Japan version

Networking
Almost all the control units of the vehicle are networked via data bus systems (CAN, D2B).
What this means is:
- There is no direct electrical connection between a sensor (e.g. exterior lamp switch (S1), in-car temperature sensor (N22b1)) and the actuated device (e.g. right front lamp unit (E2), in-car temperature sensor fan motor (N70m1)).
- The cables of the sensors are connected to the nearest control unit.
- Input signals are interpreted here to generate a corresponding message which is delivered to the data bus system.
- This message is received by one or several other control units.
- These control units then actuate the respective devices (e.g. right front lamp unit (E2), in-car temperature sensor fan motor (N70m1)).
- In certain cases, various received messages are also combined in a control unit to form a new message. The new message is then also available for the other control units on the data bus.

Basically 3 data bus systems are involved in the networking:
- Control Area Network bus class B (interior) (CAN-B) 83.5 kbit/s
- Control Area Network bus class C (engine compartment) (CAN-C) 500 kbit/s
- Digital databus (D2B) 560 kbit/s

CAN
CAN stands for "Controller Area Network." This is an electrical data bus system for carrying data over two wires.
There are two CANs:
- The CAN-B (interior) for the systems in the vehicle interior (e.g. power window function, convenience functions) and
- The CAN-C (engine compartment) for the drive and chassis systems.
Higher requirements are placed on CAN-B (interior) with regard to transfer rate and immunity to interference.

D2B
The Digital Data Bus (D2B) is a fiber-optic bus system. In this system, the data are transmitted over fiber optic cables to the connected control units. The control units for communication are connected to the D2B.
e.g.:
- COMAND operating, display and control unit (A40/3)
- Sound amplifier (A2/13)
- CD player with changer (A2/6)

Data transfer between different data bus systems
The data exchange between the CAN-B (interior) and the CAN-C engine compartment) takes place over the EIS control unit (N73), which acts as an interface (gateway).
The EIS control unit (N73) also serves as interface between the control units on the CAN-C (engine compartment) and the line to the STAR DIAGNOSIS test connector.
The data exchange between the CAN-B (interior) and the D2B takes place via the radio (A2) or via the COMAND operating, display and control unit (A40/3).

Although the instrument cluster (A1) is connected to both CAN-B (interior) and CAN-C (engine compartment) and exchanges data with both databus systems, it does not act as an interface (gateway) between the two databus systems.

The internationally standardized network management "OSEK" Open Systems and the Corresponding Interfaces for Automotive Electronics) is used for all control units of CAN-B interior).