Bit-Serial Data Interface (BSD)

Bit-serial Data Interface (BSD)

The bit-serial data interface is a single-wire data bus with a data transfer rate of 1.2 kBd.
The following components are connected across the bit-serial data interface with the DME/DDE control unit:
- Alternator (varies according to version)
- Intelligent battery sensor (depending on model series)
- Preglow control unit (on diesel engines prior to breakpoint for DDE7)
- Electric coolant pump (depending on variant)
- Oil condition sensor (depending on variant)

Only DDE control unit: Each component connected across the BSD is connected to its own pin on the DDE control unit. However, these pins are interconnected in the control unit.

Function
The following data is interchanged between the DME/DDE and the connected components:
- Functional requirements from the DME/DDE to the components
- Identification data of the components to the DME/DDE
- Operating values of the components and their functions to the DME/DDE
- Fault messages of the components to the DME/DDE

Diagnosis
The DME/DDE monitors the communication across the bit-serial data interface to the connected components. This means that line faults are also detected.
The connected components have their own diagnosis functionality and monitor the following:
- The executed functions are monitored for faults (e.g. faulty preheating circuit for the preheating control unit)
- Internal faults in the components
If a component detects a fault, it reports the fault across the bit-serial data interface to the DME/DDE. The DME/DDE then enters the fault in the fault memory.