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

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

In the digital data bus (D2B) the radio (A2) or the COMAND operating, display and control unit (A40/3), for vehicles with code (352a) COMAND operating and display system is the master unit and it also serves as an interface (Gateway) to the CAN interior (CAN-B). For this purpose, signals arriving at the master unit are converted such 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).

Conversion of the optical pulses into electrical signals and vice versa is conducted by the optical transmitter and receiver diodes, which are integrated into each component of the digital data bus system (D2B). The electrical signals are received or transmitted by the chip of the digital data bus system (D2B) as "D2B log". Because of the high transfer rate, the digital data bus (D2B) can transfer source data (audio signals) and control data (command signals) simultaneously. The source data are transmitted synchronously as 32 bit blocks into the subframes. By contrast, control data are transferred asynchronously. It is divided up, 2 bits per subframe, and distributed among a number of subframes. The control data are provided with an address, which indicates for which components in the digital data bus (D2B) the data are intended.

After reception by the target component, the individual data packages are recompiled in the component and can then be processed. A data frame can therefore contain highly differing types of information (source and control data from all components 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).