Audio gateway control unit, function - GF82.62-P-3102-04T

The audio gateway control unit (N93/1) is the central audio communications interface within the media-oriented system transport (MOST).

Depending on the equipment, the control commands are initialized by the following operating units and the control commands are transmitted via the MOST ring to the audio gateway control unit (N93/1):

• COMAND operating, display and controller unit (A40/3) with code (527) COMAND APS with single DVD drive (with navigation) or with code (530) COMAND APS USA (with navigation system)
• Radio control panel and navigation unit (A2/56) with code (525) MB Audio 50 APS radio

Scope of function:

• AM/FM reception
• Tone processing and amplification
• Realization of data exchange between MOST and Controller Area Network bus class B (interior) (CAN-B)
• Diagnostic interface

Function conditions:

• Circuit 15R ON
• Authentication positive
• No undervoltage or overvoltage

AM/FM reception 

If the user selects a certain radio station on the COMAND operating, display and controller unit (A40/3) with code (527) COMAND APS with single DVD drive (with navigation system) or with code (530) COMAND APS USA (with navigation system) or the radio control panel and navigation unit (A2/56) with code (525) MB Audio 50 APS radio, a request is transmitted to the audio gateway control unit (N93/1) via MOST, whereupon the integrated radio tuner generates an oscillating circuit to receive the particular transmission frequency.

Via the radio receiver in the audio gateway control unit (N93/1) the corresponding radio frequency signals of the FM, MW, LW, SW frequency ranges are filtered out and passed on to the integrated audio processing stage and audio amplifier stage.

Sound processing and amplification 

The control commands for audio sound and volume control coming from the COMAND operating, display and controller unit (A40/3) with code (527) COMAND APS with single DVD drive (with navigation system) or with code (530) COMAND APS USA (with navigation system), or the radio control panel and navigation unit (A2/56) with code (525) MB Audio 50 APS radio, as well as all transmitted audio signals of the system components are transmitted via MOST to the audio gateway control unit (N93/1). The integral audio processing and amplification stage digitizes and processes the incoming signals and amplifies them before outputting them to the speakers.

Dynamic range optimization (DRO) microphone input 

Connection for the sound amplifier microphone (B25/6) for automatic vehicle interior noise adaptation "Dynamic range optimization (DRO)". With the aid of the sound amplifier microphone (B25/6), which is connected directly to the audio gateway control unit (N93/1), the noise level in the vehicle interior compartment is measured. The volume of the music output signal is continuously adapted to this noise level. In order to do this, the audio gateway control unit (N93/1) must be able to detect, which signals in the measured level are driving noise and which are audio signals. This takes place by means of a comparison of the sound amplifier output signal with the measured signal. A simple way of looking at it is to regard the difference in both signals as being the driving noise level.

Interfaces 

The audio gateway control unit (N93/1) is used as an interface between MOST and CAN-B. Data which are read in e.g. by the instrument cluster (A1) and placed on the CAN-B, can be made available on the MOST as a result.

Fault management of the MOST components 

The device is the central diagnostic interface for the entire MOST. During operation, the system stores all errors which occur in the non-volatile memory. These faults can only be read out using STAR DIAGNOSIS via the data link connector (X11/4). Via the central gateway control unit (N93), the diagnosis data are transmitted directly to the CAN-B.

The audio gateway control unit (N93/1) recognizes the diagnosis command and converts the incoming data into a message compatible for MOST. The diagnosis of all MOST components is controlled by the audio gateway control unit (N93/1).

Each MOST component has its own diagnostic trouble code memory.