Revision 1.1 Appendix B – Application Note Page B3
1 Introduction
The Society of Automotive Engineers (SAE) has developed an electronic communication
networking standard for the automotive industry called J1939, which is used on many larger
diesels and some gasoline engines. Likewise, the National Marine Electronics Association
(NMEA) has developed an electronic communication networking standard for the marine
industry called NMEA 2000
®
, which is used for navigation information as well as other vessel
data such as engine information. These two networks are now beginning to coincide more and
more on vessels and Maretron has developed a gateway for bridging the two networks
together via its J1939/NMEA 2000
®
gateway (J2K100). This application note provides a basic
overview of the two networks and how the J2K100 is used to bridge engine and genset
information from the J1939 network to an NMEA 2000
®
network.
2 NMEA 2000 Network Basics
An NMEA 2000
®
network consists of two or more nodes (electronic boxes) interconnected
together using NMEA 2000
®
approved cable and connectors. A typical NMEA 2000
®
network
is shown in Figure 1.
Figure 1 – Typical NMEA 2000
®
Network
The “trunk” or “backbone” (horizontal cable and connectors shown in Figure 1) usually runs
stem to stern throughout the vessel with individual components connected as “drops” or
“stubs” (vertical cable and connectors shown in Figure 1). NMEA 2000
®
networks can have as
many as 50 drops throughout the vessel containing virtually any vessel information (engines,
batteries, AC systems, tanks, rudder position, compass, GPS, depth, AIS data, etc.). Each end
of the trunk or backbone is connected to a termination resistor (121Ω), which is used to
terminate the line in its characteristic impedance to prevent reflections or ringing on the
network. NMEA 2000
®
cables and connectors contain 5 conductors, two for power and ground
(12Volts), two for data, and one for shielding.
Maretron Tank
Level Adapter
(TLA100)
Maretron Micro
Powertap Tee
(M82516-M0x0)
Maretron
Display
(DSM200/DSM250)
Power/Shield
Connection
Maretron Micro Double
Ended Cordsets
(MDND22A-M0x0)
Maretron Micro
Male Terminator
(MDND100)
Maretron Micro
Male Terminator
(MDND100)
Maretron
Micro Tee
(MMICT555)
(23 strony)
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