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 module:

• Alternator
  
• Intelligent battery sensor (depending on model series)
  
• Combustion preheating control module (on diesel engines but not DDE7)
  
• Electrical coolant pump (depending on variant)
  
• Oil condition sensor (depending on variant)
  

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

Function

The following data is interchanged between the DME/DDE and the connected components:

• Function commands 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 wire 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. defective preheating circuit for the combustion preheating control module)
  
• 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.