Control Unit Interface

OPERATION
General
The Electronic Throttle Control (EML) control unit sends data to and receives data from other control units via various lines (interfaces). In many cases, data transfer requires more than simple "ON"/"OFF". Dynamic values must also be represented up-to-date. A square-wave voltage is therefore used for several lines to facilitate data exchange between EML, Digital Motor Electronic (DME), Electronic Transmission Control (EGS), Automatic Stability Control (ASC) and the instrument cluster.

Interface to ASC
The EML control unit is linked via three lines to the ASC control unit. By way of the Throttle Valve Setting (DKV) signal it informs the ASC control unit of the position of the throttle valve. The signal is a square-wave voltage with fixed frequency and variables pulse duty factor. Via the two other lines Throttle Reduce (DKR), Throttle Increase (DKE), the ASC control unit informs the EML system when a change in the throttle valve angle is necessary. This status is also signalled to the EML control unit by way of a square-wave voltage with fixed frequency and variable pulse duty factor. In order to facilitate external data exchange, when the ignition is switched on, synchronization takes place between the EML and ASC control units on these three lines (DKV,DKR,DKE). If this synchronization does not take place, then throttle valve intervention by the ASC control unit is also not possible.

In the case of vehicles equipped with EML, the signals of the throttle valve (throttle switch) are not sent by the EML throttle valve to the EGS and DME control units. This information is sent from the EML control unit to the EGS and DME control unit.

Interface to EGS
The EGS control unit is informed by the EML as regards the position of the throttle valve via the DKV line (DKV = throttle valve setting). This line is the same as that leading to the ASC control unit. Also the kick-down position of the Pedal Value Sender (PWG) does not go from the switch to the EGS control unit, but rather via the EML control unit. The EML system switches over to a corresponding characteristic map for the S-program of the EGS control unit. The information "program switch at S-program" comes directly from the program switch to the EML control unit.

Interface to DME
Direct data exchange between EML and DME takes place via seven lines. One line each is provided for the information Idle Signal (LL) and Full Load (VL) to the DME 1...6 cylinder and DME 7..12 cylinder. Three further lines receive the ti signal 1...6 cylinder and the Engine Speed Signal (TD) signal from the DME control unit 1...6 cylinder. The Injection Signal (ti) 7...12 cylinder comes from the DME control unit 7...12 cylinder.

Interface to to Instrument Cluster
The EML system features a line link (3 lines) to the instrument cluster to facilitate operation of the Cruise Control (FGR) and to maintain the stored information in the EML control unit. The EML receives the current road speed from the instrument cluster by way to the speed-A signal. The EML memory receives a voltage supply in order to retain the stored information in the EML when the ignition is switched off. The voltage supply is routed via the two special lamps (EML warning lamp) soldered in the instrument cluster. The two lamps are linked to the EML system via two separate lines.