Digital Data Bus (D2B)

Advantages of Bus System

With the wiring of the individual electrical and electronic components (standard wiring) as hitherto, each control module is connected directly to all sensors and actuators, from which it receives measured values or which are activated by it.

Under some circumstances this can lead to very long or redundant cable sections.

A bus system offers the following advantages compared with standard wiring:

Advantages
Lower cost of wiring
Sensor cables need only be routed to the nearest control module where the measured values are processed into a data telegram and transferred to the data bus.
An actuator can then be activated by a different control module which receives the data telegram via the data bus and from it calculates a manipulated variable for the actuator.

Improved electromagnetic compatibility (EMC)

Fewer plug connections

Fewer pins on the control modules

Weight saving

Fewer sensors
Signals from one sensor (e.g ECT sensor) can be used several times

Better diagnosis
As signals from one sensor are used several times (e.g. vehicle speed signal), in general the sensor or control module which processes the signal is defective, if all systems which use the signal indicate a fault
If only one system indicates a fault, although the signal is used several times, the fault is usually in the processing control module or the actuator.

Fast transmission rates
Up to 1 Mbit/s for a cable length of max. 40 m (but not currently used at Mercedes-Benz).
Transmission rates of 83 to 500 kbit/s are used at Mercedes-Benz.

Several messages can be transmitted in sequence on the same bus

Standard Wiring Block Diagram





Each control module requires its own sensors and actuators and is connected to them directly.

If a signal is required several times, either the functions must be combined in one control module, or the same signal must be recorded redundantly by several sensors.

Bus System Block Diagram





All control modules are connected to each other via the data bus. A control module receives a measured value from a sensor, prepares a data telegram from it and transfers it to a data bus.

Each additional control module can read and process the data telegram.