CAN data bus, function - GF54.00-P-0005VA

MODEL 209 with ENGINE 272.960 

22.3.07

C  AN stands for "C  ontroller A  rea N  etwork". This is an electrical bus system for carrying data over two wires.

The tasks are:

• Data exchange between individual control units
• Readying sensor signals for several systems
• Reducing the number of electrical lines
• Improving the electromagnetic compatibility (EMC)

The CAN data bus consists of a special twisted two-core data line that connects all CAN subscribers (control units) in parallel. The two lines of the data line must not be swapped (low level/high level). The motor electronics (N3/10) control unit is always a consumer with regard to bus adaptation.

A 120 Ω terminating resistor is therefore installed in the motor electronics control unit.

The data are transmitted digitally over the CAN databus at various intervals. The individual data blocks are defined in a data protocol and it is specified which data are received or transmitted by a control unit. Each connected control unit is able to transmit or receive data (bidirectional bus).

The sum of the data blocks, the short break between the two transfer intervals and other properties of the CAN data bus are checked constantly. Detected faults are stored and placed in the fault memory.

In the vehicle a distinction is made between the fast (500 kbit/s) engine compartment data bus and diagnostic CAN-data bus and the slower (83.3 kbit/s) interior CAN data buses.

The new control unit must be coded when a control unit is replaced. This control unit coding takes place via a STAR DIAGNOSIS menu.

The international standardized network management "OSEK" (O  pen systems and their I  nterfaces for E  lectronics in motor vehicles) is used for all control units of the CAN data bus.