Data transfer, function - GF82.00-P-2000A

MODEL 129 as of 1.6.98, 163, 168 as of 1.9.98, 170, 202 as of 1.6.98, 203, 208, 210 as of 1.6.98, 215, 220 

The Digital Data Bus (D2B) contains the master unit, e.g. the radio (A2) except for model 129, and model 202, which triggers all the components in the Digital Data Bus system (D2B). The master unit also serves as an interface (Gateway) to the CAN interior (CAN-B). For this purpose, signals arriving at the master unit are converted so that they can be transmitted from the Digital Data Bus (D2B) to the CAN interior (CAN B) and vice versa. Moreover, the master unit serves as a timing circuit which provides the clock pulse with which the information frames are transferred on the Digital Data Bus (D2B). A frame consists of 2 subframes. A series of many data frames contains the complete information for proper operation of the components located at the Digital Data Bus (D2B). The conversion of optical pulses into electrical signals and vice versa is done by transmitter and receiver diodes, that are integrated into each component. Each of the components receives or transmits the electrical signals from the chip of the Digital Data Bus system (D2B) as a "D2B log". Source data and control data are transmitted.

The source data are transferred synchronously, for example as present on a music CD, as 32 bit blocks into the subframes. By contrast, control data are transferred asynchronously. They are divided up (2 bits per subframe) and distributed over several subframes. The control data are provided with an address, which indicates for which components the data are intended in the Digital Data Bus (D2B). The individual data packages are joined together again in the components and they can then be processed. A data frame can therefore contain highly differing types of information (source and control data from all components mounted in the digital data bus (D2B)). The transmission and reception diodes as well as the digital data bus (D2B) chip are switched off when not required in order to reduce the quiescent current (sleep mode). Switch-off is accomplished immediately when the master unit or circuit 15 is switched off. After restart, the digital data bus system (D2B) can be activated either by the components or by the master unit by means of an electrical signal in the wake-up line for optical data transmission.

Regardless whether the information is intended for a component, it feeds an edited light signal back into the digital data bus (D2B) at full intensity (repeater function).