GF00.19-P-0001GZJ Overall Network (GVN) Function
GF00.19-P-0001GZJ Overall Network (GVN) Function
- except CODE (498) Japan version
Overall network
The further advancement of driver information systems is reflected in the demands placed on data bus systems. A data bus is a data collection line, the data of which can be used by all the control units connected.
Function
Most control units of the vehicle are linked to each other via data bus lines, in other words there is no direct electrical connection between a sensor and the executing actuator.
A corresponding message (data) is generated using the sensor signal and made available to the data bus system. However, the data flow must be controlled using an access procedure (log) if all control units utilize a common bus line.
Data bus systems
6 data bus systems are involved in the networking:
- Controller Area Network bus class B (interior)
- Controller Area Network bus class C (drive)
- Controller Area Network bus class D (diagnosis)
- Controller Area Network bus class H (vehicle dynamics)
- Media Oriented System Transport (MOST)
- Local Interconnect Network bus
The operational field is differentiated as follows:
- CAN-B links the control units of systems located in the vehicle interior (e.g. power windows, heated rear window etc.).
- CAN-C links the control units for the drive and chassis systems (e.g. engine, transmission control etc.).
- CAN-D links the central gateway control unit with the data link connector to perform diagnosis on all networked control units. Moreover, the emergency call system control unit can be addressed over this CAN bus.
- CAN-H links the chassis system (ESP) and the distance control system (Distronic control unit).
- MOST links the control units of the audio systems and navigation systems (e.g. telephone, voice control etc.) via a fiber optic cable.
- The LIN bus is used where rather simple control and monitoring tasks are to be performed in the vehicle.
Higher requirements are placed on the CAN-C with regard to immunity to interference, e.g. with respect to electromagnetic effect or radiation and the data transfer rate.
CAN bus systems
CAN bus systems refer to double-wire bus systems. They differ from one another in terms of transfer rate. The CAN B bus is the slowest.
MOST bus
The MOST bus is an optical bus system. Here the data are transferred via fiber optic cables to the connected control units for information, navigation, and communication systems. It has the fastest transfer rate.
LIN bus
The LIN bus is a single-wire bus system. Compared to the other bus systems, the LIN bus is slow. It is used between the multifunction steering wheel and the steering column module as well as in the air conditioning system. Likewise, it can be found between the upper control panel control unit and the lower control panel control unit as well as between the upper control panel and the rotary light switch.
Data exchange between data bus systems
The radio or the COMAND operating, display and controller unit forms the interface (gateway) for data exchange between the MOST and CAN-B. The central gateway control unit is the interface for data interchange between the CAN-B and the CAN-C.
The central gateway control unit is also the CAN-D interface to the data link connector. The control units connected to a wide variety of system buses can be tested using STAR DIAGNOSIS.
The steering column module, the instrument cluster and the EIS [EZS] control unit are connected with the CAN B as well as with the CAN C. However, they do not act as an interface (gateway) between the two data bus systems. The steering column module reads in the switch actuations on the steering column module and all button actuations on the multifunction steering wheel (MFL) over the LIN bus and places them on the CAN-B. The angle of the steering wheel is measured by the steering angle sensor (N49) and transferred to the CAN C bus via the steering column module.