GF82.00-P-2000A Data Transfer, Function

GF82.00-P-2000A Data Transfer, Function

The digital data bus (D2B) includes a master unit, e.g. the radio (A2) except on model 129 and model 202, which actuates all the components in the digital data bus (D2B) system. The master unit also acts as an interface (gateway) to the CAN interior (CAN-B). To this end, the signals arriving at the master unit are converted such that they can be sent from the digital data bus (D2B) to the CAN interior (CAN-B) and vice versa. Furthermore, the master unit acts as a clock generator which sets the cycle, with which the information sections (data frame/frames) are sent to the digital data bus (D2B). A frame consists of 2 subframes.The sequence of many frames then contains the full information content for trouble-free operation of components connected to the digital data bus (D2B). Light pulses are converted into electrical signals and back again by means of the optical transmitter and receiver diodes, which are integrated into every component. In the respective component, the electrical signals are then received by and sent from the chip of the digital data bus (D2B) system as "D2B protocol". The source data and check data are transmitted.

The source data is transmitted synchronously, as, for example on a music CD, as blocks of 32 bits in subframes.By contrast, control data is transferred asynchronously. It is split up (2 bits per subframe) and distributed across several subframes. The control data is provided with an address, which indicates the components for which the data is intended in the digital data bus (D2B).The individual data packages are combined again when received in the component where they can then be processed. A data frame can therefore contain the most varied of information (source and check data of all the components installed in the digital data bus (D2B)). The transmission and reception diodes as well as the digital data bus (D2B) system chip are switched off when not required to lower the quiescent current (sleep mode). They are switched off immediately after the master unit is switched off or at "circuit 15 OFF". When started again for optical data transmission, the digital data bus (D2B) can be activated either through the components or the master unit by an electrical signal from the wake-up line.

Irrespective of whether data is intended for a component, a processed light signal at full intensity feeds the data into the digital data bus (D2B) (repeater function).