Parameterizable special module (PSM), function

W54.21-1064-09

1 K-line to K-line systems

2 Vehicle CAN bus, waistrail

3 Vehicle CAN bus, cab rear wall

4 Vehicle CAN bus, flame starting system

5 Vehicle CAN bus, engine

6 Vehicle CAN bus, brakes

7 Body electronics AUF

8 Trailer electronics ANH (planned at a later date with code EM8)

A3 Drive control (FR) control unit

A4 Flame starting system control unit

A6 MR/PLD control unit

A7 Base module

A40 SRS control unit

A43 FFB control unit

A44 EDW control unit

A50 Communications interface control unit

A52 HPS shift force assist

control unit

P2 Instrument

X13 Diagnostic socket

Z1 CAN star point, cab waistrail

Z2.1 CAN star point, cab rear wall

A8 SIL control unit

A10 ABS control unit

A11 BS/EPB control unit

A14.1 NR/ENR control unit

A14.2 NR/WR control unit

A16 GS/EPS control unit

A20 Retarder control unit

A22 PSM control unit

A23 KSA/ZV control unit

A28 Axle modulator

A30 WS/FSS control unit

A31 ZHE warm air heater unit

A34 SIR control unit

If a vehicle is equipped with one power take-off, it is generally controlled by the drive control (FR) control unit (A3).

Vehicles equipped with more than one power take-off require the parameterizable special module (PMS) to control the PTO. The PSM control unit (A22) is linked with the other control units in the vehicle within the Integrated Electronic System (IES) over the waistrail vehicle CAN bus (2) and over the cab rear wall vehicle CAN bus (3).

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The link between the waistrail vehicle CAN bus (2) and the cab rear wall vehicle CAN bus (3) is established over the cab waistrail CAN star point (Z1) and over the cab rear wall CAN star point (Z2.1).

All participating control units speak the same language, the CAN language. They can therefore understand the messages from the other control units.

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The PSM control unit (A22) serves as an interface to the
vehicle CAN bus for control units with no vehicle CAN bus connection of their own, but which want to communicate over the vehicle CAN bus. This means that the PSM control unit (A22) can read messages from the vehicle CAN bus and translate them into other switching signals, which it then relays on to the relevant outputs that are scanned by the body electronics. In the other direction it is able to receive non-CAN bus signals from the body electronics, convert them into CAN bus signals and send them to another control unit within the IES.

The factory setting has the PSM control unit (A22) connected with the power supply and the vehicle CAN bus.

Only the inputs and outputs actually connected are activated. The PSM control unit (A22) is only adapted to the corresponding body when it has been connected to the body electronics and the parameters have been set by the body manufacturer.

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This provides the body manufacturers with an interface which enables them to use the vehicle CAN bus to acquire selected data that can be used to operate the body.

The PSM control unit (A22) with diagnostic capability evaluates and stores any faults which occur. It reports the current fault over the vehicle CAN bus (3) to the instrument (P2), which displays it on the red display field.

The diagnostic system STAR DIAGNOSIS can be connected via the diagnostic socket (X13) in order to transfer data, to reset displays and to incorporate or modify changeable parameters with the PSM control unit (A22).

The inputs and outputs of the PSM control unit (A22) are assigned certain specific basic functions. These basic functions can be activated or deactivated by means of parameterization.

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Basic functions of control unit inputs:

 Engine start: Initiates the engine start.

 Engine stop: Initiates the engine shutoff.

 Starter lockout: The engine cannot be started either externally or with the ignition key.

 ADR enable: Enables possible working speed regulation in the drive control (FR) control unit (A3).

 ADR request: Requests working speed regulation (ADR).

 Feedback "PTO 1, PTO 2, PTO 3": If the power take-off PTO1 and/or PTO2 and/or PTO3 is engaged, the indicator lamp in the appropriate switch and the corresponding display in the instrument (P2) are actuated.

 Engine brake lockout: When actuated, this prevents operation of the engine brake.

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 Fixed speed 1, 2, 3: Initiates engine speed regulation at one of the three fixed speeds. Condition: The ADR must be switched on. If more than one fixed speed is selected, the lowest is adopted.

 Remote clutch control: Initiates opening of the clutch.

 Step plate switch: When actuated, initiates a speed limit and disables reverse gear (vehicles with gear control GS only) or actuates a warning buzzer if reverse gear is engaged.

 Hand throttle actuator: An engine speed specification is sent to the drive control (FR). Between the zero and maximum settings of the hand throttle actuator, a linear reference engine speed is established starting at the minimum engine speed of the hand throttle actuator and ending at the maximum engine speed of the hand throttle actuator. The values for the engine idling speed specification and the current engine cut-off speed are read from the vehicle CAN message from the drive control (FR).

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 Actuate backup lamp: When actuated, switches on the backup lamp.

 Request "PTO 1, PTO 2, PTO 3": The input is energized by actuation of the corresponding power take-off switch and requests engagement of the selected power take-off.

 Increase engine speed: Initiates the engine speed increase.

 Reduce engine speed: Initiates the engine speed reduction.

 Engine speed off: Switches off the engine speed activated by N+ or N-.

 Shutoff control panel: Isolates the control panel from the PSM control unit (A22) by software.

 Retarder status: Provides information on the status of the retarder, which has no vehicle CAN bus capability.

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Basic functions of control unit outputs:

 PTO engaged: Output is energized when one of the power take-offs is engaged.

 Neutral position: Output is energized when the transmission is in neutral.

 Idle throttle: Output is energized when the accelerator pedal is not actuated.

 Kickdown: Output is energized when the foot throttle actuator is in the kickdown position.

 D+ switched: Output is energized when the generator outputs the signal D+.

 Retarder shutoff: Output is energized to switch off the retarder.

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Basic functions of PPM/PWM outputs:

 Engine speed signal: Outputs the engine speed as a PPM signal.

 Vehicle speed signal: Outputs the vehicle speed as a PPM signal.

 Engine torque setpoint signal: Outputs the accelerator pedal position (the desired engine torque) as a PWM signal.

 Speed limit "PTO 1, PTO 2, PTO 3, live PTO 1, live PTO 2": Actuation causes the speed to be limited to one of the five stored maximum speeds. If more than one maximum speed is selected, the lowest is adopted.

 Min./max. rpm limit "PTO 1, PTO 2, PTO 3, live PTO 1, live PTO 2": Actuation causes the rpm to be limited to one of the five stored limit speeds. If more than one limit speed is selected, the highest min. and lowest max. speeds are adopted.

 Torque limit "PTO 1, PTO 2, PTO 3, live PTO 1, live PTO 2": Actuation causes the torque to be limited to one of the five stored maximum torques. If more than one maximum torque is selected, the lowest is adopted.

 Gear lock (only vehicles with gear control GS): Causes the gearshift to be locked.

 Accelerator pedal lock: Causes the accelerator pedal to be locked.

 Splitter group output (only vehicles with gear control GS): Changes to the required splitter group when the power take-off is engaged.