GF82.00-P-0001R Digital Data Bus (D2B), Function
GF82.00-P-0001R Digital Data Bus (D2B), Function
Component Identification:
Do not kink fiber optic cable, route over sharp edges or bend in smaller radii than 25 mm.
Tensile forces on inserts must not exceed 65 N.
The fiber optical cable must not be exposed to temperatures greater than 85 °C or lower than -40 °C. Do not squeeze fiber optical cable, in other words do not compress with clamps or tie straps.
Digital Data Bus (D2B )
The Digital Data Bus (D2B) is a data bus system (data transmission system) that uses optical information transmission. The data are transferred using light pulses. These are transmitted to the components connected to the bus system via a fiber optical cable (such as: CD player with changer (A2/6), voice control system (VCS) and the telephone interface (A34/4)).
Commands given to the components, e.g., push the "Play" button on the radio (A2) (command for the CD player with changer (A2/6)) have to be converted into light pulses (optical information) via the D2B for relaying. The light pulses are then converted into electrical signals again for further processing in the receiver components and the command is executed.
Because of its fast transmission rate, the D2B can transmit source data (e.g.: music from CD player with changer (A2/6)) and control data (e.g.: "Play" command for CD player with changer (A2/6)) simultaneously. This reduces the quantity of wiring considerably.
The connected components therefore require only two lines for the power supply (electrical), two lines (input/output) for the D2B fiber optic cable and one line for the wake-up signal (electrical), instead of the 7 to 8 lines that were required previously.
Several low frequency (LF) signals can also be transmitted via the fiber optic cable without affecting the information content, e.g.: music of CD player with changer (A2/6) and telephone handset (A34) voice information.
Data transmission using fiber optic cable has many advantages:
^ extremely high data transfer speed
^ Prevents tapping and cross-talk
^ Data transmission is not sensitive to electromagnetic radiation
^ Short circuiting cannot occur
^ Potential-free connection of bus components
^ No oxidation
^ Low weight of fiber optical cable
^ Minimum diameter of wiring harness
The D2B has a closed ring structure. The components are arranged in a ring line (series circuit). This arrangement is model- specific:
In model 230 these are:
1. Radio (A2) or COMAND operating, display and control unit (A40/3)
2. Sound amplifier (A2/13)
3. CD player with changer (A2/6)
4. Telephone interface (A34/4) or D2B telephone transmitter/ receiver (A35/13) or TELE AID control unit (A35/8) (ECE) or E-call control unit (A35/8) (with code 491 USA version, code 498 Japan version)
5. Voice control system (VCS)
This component order must be strictly adhered to. If the ring subscribers are changed, an error message is generated. But the system may still be operational.
With this system, information is transferred only in one direction. This means that the light pulses for the sound amplifier (A2/13) run through all the components in the ring before they reach the sound amplifier (A2/13).
In the examples that are shown it can be seen that the radio or the COMAND operating, display and control unit (A40/3) is in first position. It always has a supervisory function in the D2B ring (master function), whereas the rest of the components have a subordinate function (slave function).
When the system is first put into operation, a system test is performed. The individual components and the order there of in the D2B ring are registered by the radio (A2) or the COMAND operating, display and control unit (A40/3).
A type-specific sequence is stored in the radio (A2) or the COMAND operating, display and control unit (A40/3) in the factory. The sequence of the components can be subsequently adapted in the radio or the COMAND operating, display and control unit (A40/3) using Star Diagnosis.
