MODEL   215 up to 31.8.03

Extended vehicle network The further development of driver information systems as well as the spread of video-based, driver-supported systems (e.g. backup camera, ambient sensor technology), are reflected in the requirements on bus systems. A data bus is a data collection line, the data of which can be used by all the control units connected. In automotive engineering, CAN (Controller Area Network) means that data is exchanged between all the control units in a motor vehicle via a data bus.

Function In models 215 and 220 all systems or control units of the vehicle electrics are networked to each other via databus lines. Control commands or messages are coded and introduced into the databus message- or address-orientated, whereby each system has a different priority i.e. different access rights. These coded commands or messages can only be received by control units with authorized access. The appropriate actuators are then actuated. 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 other control units on the data bus system.

Essentially, three data bus systems are involved in networking: Diagnosis CAN 500 kbit/s CAN B (CAN interior compartment) 83.5 kbit/s CAN-C (CAN engine compartment) 500 kbit/s Digital data bus (D2B ) 560 kbit/s There are two CANs: CAN interior for systems in vehicle interior (e.g. power windows, heated rear window, air conditioning, ...) CAN engine compartment for the drive/chassis systems (e.g. Electronic Stability Program (ESP), Autonomous intelligent cruise control (ART), Electronic accelerator (EA, etc.) Greater demands are made on CAN-C (CAN engine compartment with respect to resistance to interference e.g. electromagnetic effect or radiation and the high data transfer rate.

D2B The D2B (Digital Data Bus) is a fiber-optic bus system. In this system, the data are transmitted over fiber optic cables to the connected control units. Among the control units linked to the D2B are: COMAND operating, display and control unit (A40/3), radio (A2) or sound amplifier (A2/13) CD player with changer (in the trunk) (A2/6) Data are exchanged between CAN-B and the D2B via the radio (A2) or the COMAND operating, display and control unit (A40/3) Data transfer between various bus systems Data exchange between the CAN-B and CAN-C bus systems is effected up to 1.9.02 via the electronic ignition switch control unit (N73), which acts as a gateway. Changed as of 1.9.02 As from 1.9.02 the new central gateway control unit (N93) has been the interface between CAN-B and CAN-C, as well as vice versa a data logger (e.g. fault memory).

The electronic ignition switch control unit (N73) now serves the messages which are not routed by the central gateway control unit (N93). This is a "finite interface" (gateway) for exchanging data between the bus systems CAN-B and CAN-C. The central gateway control unit (N93) is also the central diagnostic interface between the control units on CAN-B and CAN-C. For this reason, it is connected directly to the STAR Diagnosis tool control line. Steering column module The steering column module (N80) is additionally connected to CAN-B and CAN-C, although it does not act as an interface (gateway) between the two bus systems. All the button operations on the multifunction steering wheel and switch operations on the steering column module (N80) are read in by the module and transmitted over CAN-B.

The driving direction is detected by the steering angle sensor (N49) and sent via the steering column module (N80) to CAN-C. These signals can pick up the drive and chassis systems. Instrument cluster The instrument cluster (A1) is networked with the engine compartment CAN and the interior CAN. Data are exchanged with both databus systems and with practically all the control units of the two databus systems. However, the instrument cluster (A1) does not act as an interface (gateway) between the two bus systems. This function is reserved for the central gateway control unit (N93).

Block diagram: Schematically displayed with equipment variants, code 352a (COMAND operating, display and control unit), 853 (MB Standard telephone), 810 (sound system) A1 Instrument cluster A2/6 CD player with changer (in trunk) A2/13 Sound amplifier A35/13 D2B telephone transmitter/receiver A40/3 COMAND operating, display and control unit

N3/9 CDI control unit N3/10 ME-SFI [ME] control unit N15/5 Electronic selector lever module control unit N63/1 DTR control unit N69/2 Right front door control unit N69/3 Left rear door control unit N70 Overhead control panel control unit N73 DI control unit

N80 Steering column module N93 Central gateway control unit The central gateway control unit (N93) is integrated into the networking (as shown in block diagram) and forms the gateway (interface) between CAN-B (CAN interior) and CAN-C (CAN engine compartment).

Data exchange for recording the wheel speeds for navigation. For the COMAND operating, display and control unit (A40/3) the wheel speeds are picked up by the two front rpm sensors at left (L6/1) and right (L6/2). The left front rpm sensor (L6/1) and right front rpm sensor (L6/2) use magnetic induction to determine each AC voltage, which is transmitted via direct lines to the ESP, SPS [PML] and BAS control unit (N47-5).

Signals are processed in the ESP, SPS [PML] and BAS control unit (N47-5) and sent as a CAN message to the CAN engine compartment. The central gateway control unit (N93) operates as an interface and transmits the CAN message to the CAN interior. If required the COMAND operating, display and control unit (A40/3) scans the message and interprets it. The instrument cluster (A1) is likewise able to take up and process this message.