GF82.00-P-0001Q Digital Data Bus (D2B), Function

GF82.00-P-0001Q Digital Data Bus (D2B), Function

Sequence of components, exemplified on model 209.4 with code (819) 6-disc CD changer, with code (810) sound system, with code (813) voice control system (VCS), with code (855) TELE AID and with code (352a) COMAND operating and display system

Component Identification:

Digital Data Bus (D2B )
The Digital Data Bus (D2B) is a data transmission system for the communication and information components, which utilizes the optical data transfer options. Data transfer is conducted by means of optical pulses, which are transferred over fiber optical cables to the connected communication and information components. Audio and command signals are converted in the source components into optical pulses and transmitted via fiber optical cables. The optical signal is converted back to an electronic signal in the target component. Because of the high transfer rate, the Digital Data Bus (D2B) can transfer audio and command signals simultaneously. Simultaneous transfer of source data and command data over the Digital Data Bus (D2B) significantly reduces the amount of cabling. The connected components require 2 lines for the voltage supply (electrical) and 2 lines (input/output) for the fiber optical cable of the Digital Data Bus (D2B) and one line for the wake-up signal (electrical).

In addition to this, the fiber optical cable can transfer several pieces of source data simultaneously (e.g. music and voice from 2 components), without compromising the data content.

Functional sequence using "Play CD" by way of example Pressing "Play" on the radio (A2) or on the COMAND operating, display and control unit (A40/3), for vehicles with code (352a) COMAND operating and display system, sends a command signal over the Digital Data Bus (D2B) to the CD player with changer (in the glove compartment) (A2/6), for vehicles with code (819) 6-disc CD changer. The audio signals from the CD player with changer (in the glove compartment) (A2/6), for vehicles with code (819) 6- disc CD changer, are then transmitted via the Digital Data Bus (D2B) as source data to the Sound amplifier (A2/13), or for vehicles with code (810), to the sound system. In the target components, the Sound amplifier (A2/13), or for vehicles with code (810), the sound system, the source data are then converted back to electrical signals and reproduced as sound.

Data transfer using fiber optical cables has the following advantages:
^ Extremely high data transmission rate
^ Prevents tapping and crosstalk
^ Insensitive to electromagnetic radiation
^ Short-circuit resistance
^ Zero potential connection of components
^ No oxidation
^ Low weight of fiber optical cable
^ Minimum diameter of wiring harness

The digital data bus (D2B) has a closed ring structure. The communication and data components are arranged here in a distributor line (series circuit). This arrangement is type-specific and is illustrated by way of an example on model 209.4 as follows:
^ COMAND operating, display and control unit (A40/3), with code (352a) COMAND operating and display system
^ Telephone transmitter/receiver and TELE AID, D2B (A35/17), with code (855) TELE AID
^ E-call control unit (A35/8), with code (855) TELE AID, with code (491) USA version and with code (498) Japan version
^ CD player with changer (in glove compartment) (A2/6), with code (819) 6-disc CD changer
^ Sound amplifier (A2/13), with code (810) Sound System
^ Voice control system control unit (A35/11), with code (813) voice control system (VCS)

The data transfer is conducted in one direction only, i.e. the optical pulses for the voice control system control unit (A35/11), for vehicles with code (813) voice control system (VCS), pass through all the components in the ring, before arriving at the voice control system control unit (A35/11), for vehicles with code (813) voice control system (VCS).

The radio (A2) or COMAND operating, display and control unit (A40/3), for vehicles with code (352a) COMAND operating and display system, within the ring structure of the Digital Data Bus (D2B) always have a higher-ranking function (master function), whereas the remaining components adopt a subordinate function (slave function). When the system is first put into operation, a system test is performed. Here the individual components and their sequence in the ring structure of the Digital Data Bus (D2B) are registered by the radio (A2) or the COMAND operating, display and control unit (A40/3), for vehicles with code (352a) COMAND operating and display system.

The Digital Data Bus (D2B) is rendered diagnosis capable by the data link connector (X11/4) via the radio (A2) or the COMAND operating, display and control unit (A40/3), for vehicles with code (352a) COMAND operating and display system.

The operating principle of the Digital Data Bus (D2B) is the same for all vehicle variants; all that changes is the sequence of components depending on the national version and equipment specification.