The ISO 11992 truck and trailer set of profiles
The ISO 11992 standard is made of four parts and defines the point-to-point truck/trailer communication. Part 1 defines the physical layer and the data link layer. The physical bus consists of unscreened twisted pair (CAN_H and CAN_L) for the transmission of the differential signals. These conductors may be part of a multi-core cable. For the physical layer the characteristic impedance has no significant influence. The total length of the bus cable is split into three parts. The signal voltage levels are different from ISO 11898-2. The voltage levels for a dominant bit are specified as 2/3-supply voltage for CAN_H and 1/3-supply voltage for CAN_L. A recessive bit is represented by 1/3-supply voltage for CAN_H and 2/3-supply voltage for CAN_L.
Part 2 specifies the parameters and messages for electronically controlled braking systems including ABS (Anti-lock braking systems) and for running gear equipment (i.e. systems for steering, suspension and tires). The analog parameters are specified by data length, resolution including engineering units and offset, data range and type (measured or status).
Part 3 specifies the parameters and messages for all other electronically controlled systems.
Part 4 of this standard defines the diagnostics services that are divided into basic and enhanced diagnostic applications. The purpose of the basic diagnostics is to provide vehicle independent identification and information. The enhanced services are truck-specific.<
The ISO 11992 standard is also suitable for road trains with multiple trailers (up to five). The address assignment procedure is initiated by the commercial vehicle and automatically assigns addresses to the towed vehicles.
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