Display/operating unit with control module, function - GF82.85-P-3114-08RB

Process keypresses 

The control buttons and switches on the function keypad on the COMAND operating, display and control module (A40/3) are read in over the microcontroller I/O ports and transferred to the central processor. Depending on the system function, the button actuations are processed in the central processor and transferred to other system components via the digital data bus (D2B) or passenger compartment CAN bus, in the form of a data telegram.

Graphic editing and image output 

The video subsystem takes over editing and output of the control displays. The control displays are output by the video subsystem internally to the monitor via the RGB output (R=Red, G=Green, B=Blue). The RGB signal contains the information and amplitudes for the three colors of red, green and blue, and a synchronization signal.

The electronic circuitry in the display unit evaluates the RGB signal and controls the individual display dots 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. Upon reaching the last line the vertical synchronization pulse is received causing the electronic circuitry to start the first line again.

Audio signal output 

The audio signals from the various sources (CD, voice output for guidance) are edited by the COMAND operating, display and control module (A40/3) and amplified for output on the vehicle loudspeakers. Final amplification of the audio signals is accomplished by the sound amplifier (A2/13). The audio source data is transmitted digitally for this purpose via the digital data bus (D2B) to the sound amplifier (A2/13).

Diagnostic interface (K line) and error management for D2B bus components 

During COMAND operation, the system stores all errors occurring in a non-volatile memory. They can be read out via the diagnostic interface K line) with the STAR diagnosis tool. Output of the errors on the display unit is not possible.

The COMAND error administration also includes the components connected to the digital data bus (D2B). For this purpose, each D2B bus component has its own DTC memory. The DTCs are transferred via the digital data bus (D2B) to the COMAND operating, display and control module (A40/3) upon request by Star Diagnosis where they can be read out via the diagnostic interface (K-line).

Navigation processor and GPS control module. 

The navigation processor is the central component of the COMAND navigation system. It is integrated into the COMAND operating, display and control module (A40/3) and calculates the vehicle location from the signals received and the vehicle route after the destination is entered.

The GPS control module is 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.

CD-ROM and CD-ROM drive 

With the aid of the integrated CD drive, data can be read from the special navigation CD or Audio CDs.

The following are contained on the navigation CD-ROM:

• Program data for execution in the navigation
• Voice data for voice output
• Map data.

The digitized map area on the CD-ROM contains towns, cities, streets, intersections and their attributes (e.g.: one-way streets and turn prohibitions). It does not contain information about company and private land, farms, housing estates and paths.

Gyrosensor 

The gyrosensor determines vehicle direction changes. It is installed in the navigation processor. Calibration is not required.

Traffic data recorder 

The integrated traffic data memory receives traffic messages via the digital data bus (D2B) (in the StarGuide mode). The data is stored for a maximum of 30 minutes, even during the COMAND run-out time, in the traffic data memory (up to 100 messages). The traffic data memory decodes the messages and transfers them to the navigation processor as required.

For synchronization tasks the traffic data recorder requires an up-to-date "location list" from the navigation computer. In the location list, each section of road and each major point (e.g. freeway exit) of the road system which is monitored in respect of traffic density, is unequivocally defined on the basis of a number. This list is stored on the CD-ROM.

It is automatically loaded (e.g. if CD-ROM is changed) from the navigation processor into the non-volatile traffic data memory.