Installation Manual

Electrical & Electronic Application And Installation Manual
Production Release Version 1.0
Page 234
18.0 Datalink Support
Both the 1200 series Tier 4 Final/Stage IV product range is supplied with a
customer J1939 CAN bus connection as part of the ECM J1 connector. The
J1939 standard is a widely used protocol, which operates on a standard
CANBus system. All J1939 enabled devices will operate on this datalink and
the remainder of this section details the basic requirements for J1939
communication. The Perkins datalink is a proprietary datalink, which can be
used with specialist devices available through Perkins aftermarket networks.
It should be noted that these are currently the only two datalinks supported by
the ECM hardware and the incorporation of the engine into systems operating
on protocols such as ModBus will require a gateway to convert the protocol to
J1939 for ECM communication.
18.1 SAE J1939
The SAE standard was initially developed for the US truck and bus industry. It
has been expanded and is now the most widely used datalink standard for
industrial power trains, with compliance from almost all engine and
transmission manufacturers.
A list of SAE J1939 documentation, which should be used as reference when
installing a J1939 network, are listed below.
SAE J1939-11 Physical Layer, 250Kbits/s, Twisted Shielded pair.
SAE J1939-15 Reduced Physical Layer, 250Kbits/s, Un-shielded Twisted
pair.
SAE J1939-21 Data Link Layer.
SAE J1939-31 Network Layer.
SAE J1939-71 Vehicle Application Layer.
SAE J1939-73 Application Layer Diagnostics.
18.1.1 Summary of Key J1939 Application Issues
This is a summary of some of the key points and answers to frequently asked
questions relating to design of a J1939 compatible network. It is intended to
give a design overview and does not in any way replace or contradict the
recommendations or design criteria contained within the SAE J1939 standard
documents.
18.1.2 Physical layer
• The data rate is 250Kbits/sec
• Twisted pair cable, of a 120Ohm impedance characteristic, should be
used throughout. Note that most commercially available twisted pair
cable is not suitable.
• It is recommend that this cable is shielded (as per J1939-11) and that
the screen is grounded at a central point in the network. Unshielded
twisted pair cable is used by some machine manufacturers, however
(as per J1939-15), offering lower cost but lower immunity to
electromagnetic noise.