The Audio System Controller (ASK) manages all the audio signals of the Top HiFi audio system. Operation of the radio and CD drive takes place at the Audio Display Panel (ADP). The radio functions and radio station data as well as CD -drive data are displayed at the Audio Display Panel (ADP). At a temperature > 70 °C, the ASK switches off. The MOST functions are then no longer available.
Station buttons: Pressing the keys on the left and right of the Audio Display calls up preset radio stations. Each of the six keys can be assigned a radio station in the FM range and one in the AM range.
Audio Display: Information on the currently set radio function and radio station data or the CD in the CD holder is displayed on the Audio Display.
AM button: Pressing the first button from the left switches the receiver to AM reception.
FM button: Pressing the second button from the left switches the receiver to FM reception.
Mode button: Pressing the third button from the left switches between radio and CD operation mode. Each press of the button calls up a different mode.
CD drive slot: Pressing the 'Eject' button causes the CD holder to move out of the CD drive slot. After a CD is inserted and the CD holder pressed in, the CD is played. Sound output takes place when the CD mode has been set using the 'Mode' button.
Eject button: Pressing the third from the right causes the CD holder to move out of the CD drive slot. The function is not dependent on the status of the control unit.
Scan buttons: Pressing the second button from the right triggers a station-search function in which counting takes place ”backwards” from the higher to the lower value. Pressing the first button from the right triggers a station-search function in which counting takes place from the lower value to the higher value. In the AM and FM mode, the radio stations are displayed in the corresponding order. In the CD mode, the numbers of the tracks on the CD are displayed.
When the Scan buttons are pressed, the ASK sends a change in status to the Control Display. The Control Display identifies the currently active audio source and sends a telegram to the relevant control unit. The telegram contains the request for executing the function: Next track (drive) or next station (AM or FM).
Volume rotary knob: Turning the knob beneath the CD drive slot influences the volume of the selected audio source. Turning to the left lowers the volume. Turning to the right raises the volume.
If a rotary movement is performed, the ASK transmits a status change to the Control Display. The Control Display identifies the currently active audio source and sends a telegram to the ASK. The telegram contains information on the level of the volume to be adjusted and the active source. This information is also sent to the Top hi-fi amplifier. The Top hi-fi amplifier controls the volume at the speakers in accordance with the information.
MFL Multifunction Steering Wheel The volume adjustment function can also be run using the multifunction steering wheel (MFL). When the louder/quieter button (+ / -) is pressed, the MFL transmits a status change across the CAN to the Control Display. The Control Display processes the status message and sends a telegram to the ASK. The telegram contains the information on the volume value and the active source. This information is also sent to the Top hi-fi amplifier. Thus, in the event of a malfunction, the location of the fault can be narrowed down to two control units.
The MOST bus (Media Oriented Systems Transport) links the audio, video and navigation systems. Information relating to function requests is transmitted to the relevant control units by means of MOST bus messages. If a control unit does not accept messages intended for it, the operation is repeated up to five times by the transmitting control unit. If a receiving control unit still does not accept the message, the action is not initiated. The ”Transmission error” fault memory is set.