The ASK audio-system controller manages all the audio signals of the audio system. The audio system comprises the stereo, hi-fi and Top hi-fi options. The ASK also accommodates the output stages of the basic speaker equipment. At temperatures above 70°C the ASK shuts down. The MOST functions are then no longer available.
Combined rotary control/push button: The entertainment function is activated and deactivated by pressing the button. The MOST network is woken with terminal R OFF. It is not possible to wake the MOST network with terminal R OFF by means of the controller.
The volume of the active audio source is adjusted by turning the button. 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. If the appropriate equipment is fitted, this information is also sent to the Top hi-fi amplifier. The amplifiers or Top hi-fi amplifiers control the volume at the speakers in accordance with the information.
MFL multifunction steering wheel: The volume-adjustment function can also be performed at the multifunction steering wheel (MFL). When the louder/quieter button (+ / -) is pressed, the MFL transmits a status change via 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. If the appropriate equipment is fitted, 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.
Auto search button: When the auto search button is pressed, 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 relevant control unit. The telegram contains the request for executing the function: next track (drives) or next station/channel (TV, radio).
Eject button: The Eject button is used to eject the sound carrier. The function is not dependent on the status of the control unit. If the control display indicates that a DVD is inserted in the Multimedia changer but cannot be ejected, the device is mechanically faulty.
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 a message intended for it, the procedure is repeated by the transmitting control unit up to five times. Nevertheless, if a receiving control unit does not accept the message, the action is not started. The ”Transmission error” fault memory is set.