Psm (Parameterizable Special Module); General; Econic Basic Parameter Data Set; Typical Applications In The Vehicle - freightliner EconicSD Technical Information

8.12 PSM (Parameterizable special module)

8.12.1 General

The chassis, engine, transmission, brake system etc. are controlled by electronic control units. Due to
the complexity of the vehicles, the individual system components (control units, sensors etc.) are no
longer connected in analog format by wiring but in digital format using a high-speed network: the
High-Speed Controller Area Network (HS CAN bus).
All the participating control units understand the messages transmitted on the CAN bus and are
adapted to the CAN language, which is known as the protocol.
The parameterizable special module (PSM) forms the interface between the vehicle and the electronic
systems of the body. It was developed to allow Truck Equipment Manufacturer to access the individual
CAN bus data.
The PSM with body interface as per 11898 is standard for the EconicSD (5 V basic, without single-wire
capability).
The parameterizable special module can read the HS CAN bus data from the messages and convert
them into both digital output signals and into CAN bus signals for the Truck Equipment Manufacturer.
In the other direction, it can receive CAN bus signals from the body electronics as well as
analog/digital signals, convert them into signals suitable for the CAN bus and forward them to
another control unit within the vehicle CAN bus network.
The PSM provides a clearly defined, diagnostics-compatible and EMC-tested interface between the
vehicle and the body. What used to be achieved through complex wiring from the Truck Equipment
Manufacturer is today accomplished through parameterization of the PSM.
The cabling on the vehicle must not be tampered with, as this would lead to fault messages from the
other control units on the CAN bus.
For customer-specific requirements, special inputs, such as external engine start/stop, or special
outputs can be translated e.g. into switching signals at the outputs provided ("high" or "low") or into
PWM (pulse width modulated) signals, which in turn can be processed further by the body electronics.
Example:

The engine speed is sent in a message by the CPC control unit and can be read by the
PSM control unit on the CAN bus. The PSM control unit converts the engine speed information
into a PPM signal and makes this available at an output.

In contrast to the example above, the PSM can convert the body's request for a fixed speed into a
CAN message and thus request the desired rotational speed.
The diagnostic-capable PSM control unit evaluates any faults which occur and saves
these. It reports the current fault to the instrument cluster via the vehicle CAN.

8.12.2 Econic basic parameter data set

An overview of the basic parameter data set upon delivery is included in the appendix.

8.12.3 Typical applications in the vehicle

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