Digital Data Bus (D2B), Function
Digital Data Bus (D2B), Function
D2B Ring:
CAUTION: Do not kink fiber optic cables, do not route via sharp edges or bend in radiuses smaller than 25 mm. Tensile forces on inserts must not exceed 65 N.
The fiber optic cable must not be exposed to temperatures greater than 85 degrees C or lower than -40 degrees C. Do not squeeze fiber optic cable, in other words do not compress with damps or tie straps.
Digital data bus (D2B)
The digital data bus (D2B) is a data bus system (data transmission system) which uses the capabilities of optic information transfer. Here, the data is transferred by light pulses. These are transferred to the components connected to the bus system (for example: CD player, voice control system (VCS), telephone. Tele Aid emergency call system) by a fiber optic cable.
It is necessary to convert commands for the components, e.g. pressing the "Play" button on the radio (command for CD player) to light pulses (optical information) for transfer via the D2B bus. The light pulses are then converted back to electrical signals in the receiving components for further processing and the command executed.
Due to its high transfer rate, the D2B bus can simultaneously transfer data sources (for example:music from CD player) and control data (for example: "Play" command for CD player). This reduces the wiring considerably.
The connected components therefore require only two leads for the power supply (electrical), and two leads (input/output) for the D2B fiber optic cable and one lead for the wake-up signal (electrical), where 7 - 8 leads where required previously. Moreover, a number of audio frequency (AF) signals can be transferred via the fiber optic cable simultaneously without any negative effects on the information contained, for example: Music from CD player and telephone voice signal.
Data transfer using fiber optic cable has many advantages:
- extremely high data transfer rate
- security against monitoring and cross-talk
- data transfer is insensitive to electromagnetic interference
- resistance to short circuit
- potential-free connection to bus components
- no oxidation
- low weight of fiber optic cable
- small diameter of wiring harness.
The D2B bus has a closed ring structure. The components are arranged in a ring circuit (series circuit). This arrangement is specific for this type of application:
In model 230, these components include:
1. Radio or COMAND
2. Sound amplifier
3. CD player with changer
4. Telephone or mobile telephone or Tele Aid system
5. Voice control system
It is absolutely necessary to observe this component sequence in the event of changes of the ring components, an error message is stored. However, the system may still be operative depending on the circumstances.
In this case information is transferred only in one direction. This means that the light pulses for the telephone run through all components located in the ring before arriving at the telephone.
From the examples listed, it is recognizable that the radio or COMAND is always the first component.Within the D2B ring, it always has a priority function (master function) while the remaining components have a subordinate function (slave function).
When the system is first started up, a system test is performed. During this test, the individual components and their sequence in the D2B ring is checked by the radio or COMAND unit.
A sequence specific for the model is stored at the factory in the radio and COMAND unit.
The sequence of the components in the radio or COMAND unit can be adapted subsequently using Star Diagnosis as an aid.