This vehicle is equipped with a CAN (Controller Area Network) system of electrical connections: it involves a software and hardware solution which is designed to efficiently manage the resources on the vehicle, allowing:

• the sharing of information between the various electronic units;

• the integration of several electronic units through one network;

• a high network information exchange speed;

• advantages in economic terms because there is a considerable reduction in the wiring and connectors inside the vehicle;

• superior standards in terms of quality and reliability.

Communication takes place through serial BUS (duplex cable) with differential signals, in which the value given to the single bit is represented by the difference between CAN-H and CAN-L voltages.

The different electronic units that make up the system, known as network "Nodes", are connected to the CAN by means of communication interfaces called transceivers. These connection interfaces, built into the electronic units, constitute the gate for sending/reading the information on the CAN or serial lines.

The main element of the CAN is the Body Computer which is entrusted with the task of "waking the network up" when the ignition key is turned to the ON position.

The Body Computer also carries out the network monitoring functions which make it possible to provide information on:

• the network activities status;

• the functional failure status of the individual electronic units (nodes);

• a possible CAN fault.

The various electronic units process the various signals coming from the corresponding sensors both for their own management and for other control units to which they are sent via the CAN.

The specific structure adopted for this vehicle consists of two CAN communication networks that connect nodes belonging to two different areas:

• C-CAN for dynamic vehicle control (high speed): bus CAN-H and CAN-L;

• B-CAN for the management of standard body functions (low speed): bus CAN-A and CAN-B.

Fitters/installers needed to fit some electronic devices not compatible with those installed in factory, this resulted in the need to use the CAN (CAN-B and CAN-C) gateways between the applications typical of Fiat Auto (FGA) and the world of FMS (Fleet Management System Interface).

The FMS interface is a standard system, developed by the main European manufacturers of commercial vehicles to make possible computerised applications, independent of the manufacturers.

The TUM control unit is therefore an interception and storage device for data and signals (sniffer), used as a gateway between CAN-B and CAN-C of the vehicle and FMS interface.

Operation of the TUM gateway involves:

• transformation 1:1 of some signals of the vehicle message map to the FMS standard – Direct Gateway -;

• the use of various vehicle signals to calculate the required FMS signals not present directly on the vehicle network – Indirect Gateway -.

For further details,

    See descriptions 5505 INSTRUMENT/GAUGE ELECTRICAL CIRCUITS