Radio and navigation unit, function - GF82.61-P-4109-04SK

The control buttons and switches of the function keyboard in the radio and navigation unit (A2/56) are read in and transmitted to the central processor. Depending on the system function the keys pressed are processed in the central processor or transmitted to the other system components via the media-oriented system transport (MOST), controller area network bus class B (interior) (CAN-B) or controller area network bus class C (engine compartment) (CAN-C) in the form of a data telegram

If the ON button on the pushbutton control is pressed the radio and navigation unit (A2/56) switches on. In each case the volume can be regulated with the pushbutton rotary switch for the audio source active. The function keys (hard keys) are used to switch over to the audio source selected by the user.

Graphic editing and image output 

The graphics subsystem handles the preparation and output of the operating masks. The operating displays are output internally to the display by the graphic subsystem via the RGB output (red, green, blue).

The information and amplitudes of the 3 colors red, green and blue as well as a synchronization signal are included in the RGB signal. The electronic circuitry in the display unit evaluates the signal and actuates the individual display pixels line by line in terms of color and intensity. A horizontal synchronization pulse occurs at the end of each line. The electronic circuitry of the display unit then starts the next line. When the last line of the display has been reached, the vertical synchronization pulse occurs; the electronics actuate the first line again.

Three fixed contrast settings can be retrieved for better perception of the display information:

• Day design
• Night design
• Driver's light

Infinitely variable brightness control is possible using a four-way adjusting knob.

Compact cassette tape drive 

The radio and navigation unit (A2/56) is equipped with a compact cassette tape drive. All sound and volume adjustments are performed via the operating unit.

Multi-standard drive for Audio CD 

With the aid of the integrated multi-standard drive data can be read from the special navigation DVD-ROM or Audio CD can be played.

AUX jack 

In the glove compartment there is an AUX jack that can be used as a connection facility for additional audio sources, e.g. an MP3 player.

DVD ROM 

The following are contained on the navigation DVD-ROM:

• Program data for execution in navigation processor
• Voice data for voice output
• Map data

Navigation processor and global positioning system (GPS) control unit 

The navigation processor is integrated into the radio and navigation unit (A2/56) and calculates the location of the vehicle from the incoming signals and the vehicle's route after the destination has been entered. The GPS control unit is a part of the navigation processor. It evaluates the satellite signals coming from the GPS antenna (A2/23) and calculates the vehicle position from this information.

At least 4 satellites are required for dead reckoning, 3 satellites are sufficient for other calculations. If these conditions for position calculation are not met, only the number of satellites appears on the display.

Turn rate sensor 

The turn rate sensor determines the direction changes of the vehicle. It is installed into the navigation processor. A calibration is not required.

The traffic data memory 

The traffic data memory is located in the radio and navigation unit (A2/56). When the "Radio Data System" and the traffic information channel are active, the uncoded traffic message data received by the radio tuner in the audio gateway control unit (N93/1) are transmitted to the traffic data recorder via MOST. The data are stored for a maximum of 30 minutes, also during the "run-on time" (up to 100 messages). The traffic data memory decodes the messages and transmits them to the navigation processor as required.

The traffic data recorder requires an up-to-date "location list" from the navigation processor for synchronization purposes. The monitory points for checking the network of roads (e.g. freeway exit) are defined by clear numbers in the "Location list". The "Location list" is stored on the DVD-ROM It is automatically loaded (e.g. if DVD-ROM is changed) from the navigation processor into the traffic data memory.

Offboard diagnosis, STAR DIAGNOSIS 

The radio and navigation unit (A2/56) has its own fault memory. When the diagnostic trouble code memory is interrogated by means of STAR DIAGNOSIS, the data are transmitted to the audio gateway control unit (N93/1) via the MOST and can then be read out via the central gateway control unit (N93) interface.

It is not possible to output faults via the display.