Service Manual DS 85
© Hirschmann Rev.G 10/05/15 190166_G.DOCXG
13 CAN-BUS COMMUNICATION
BRIEF DESCRIPTION OF A CAN BUS SYSTEM
CAN stands for “Controller Area Network”. Its intended use is as a serial bus system for a network of
controllers. Each controller connected through a CAN chip is called a "node" and is mostly used to
acquire data from a sensor. All nodes are connected to a common bus and all nodes are able to
simultaneously read the data on that bus. Also, all nodes are able to transmit data on that bus
however only one node at a given time has write access to the bus. If the message is relevant, it will
be processed; otherwise it is ignored. The unique identifier also determines the priority of the
message. The lower the numerical value of the identifier, the higher the priority.
The cable bus is a twisted pair of shielded wire. Data can be transmitted in blocks from 0-8
bytes at a maximum transfer rate of 1 Mbit/s for networks up to 40 meters. For longer network
distances the maximum transfer rate must be reduced to 50 Kbit/s for a 1 km network distance.
CAN will operate in extremely harsh environments and the extensive error checking
mechanisms ensure that any transmission errors are detected.
The system measures the length of the main boom, the angle of the main boom, and the pressures of
the lift cylinder via a CAN-Bus connection. Since this is a digital bus connection, it is not possible to
measure the signals on the bus with a multimeter. Instead, the LMI provides you with error codes that
give you an indication of the bus state.
The error codes are one of the following:
E61 Error in the CAN bus data transfer for all CAN units
E62 Error in the can bus data transfer of the pressure transducer sensor unit
E63 Error in the can bus pressure transducer sensor unit
E64 Error in the can bus data transfer of the length/angle sensor unit
E65 Error in the can bus length/angle sensor unit
Block Diagram
The block diagram tries to clarify that: If the CU does not see any CAN-Bus component, it will report
an E61. If it sees only the cable reel, it will report an E62 (pressure transducer missing). If it sees only
the pressure transducer, it will report an E64 (cable reel missing). E63 means that the pressure
transducer is available, but is reporting an internal error. E65 means that the cable reel unit is
available, but is reporting an internal error.
DS 85
Console/
CU
Angle sensor box
CAN-Bus
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