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2.5.3 NMEA 2000
Of all the SAE J1939 derivatives, NMEA 2000 seems to be the only consequent and straight-forward adaptation of J1939. While taking advantage of a proven and ingeniously designed protocol, NMEA 2000 defines only its own messages.
NMEA 2000 is used for marine data networks providing communication between marine specific electronic devices such as depth finders, chartplotters, navigation instruments, engines, tank level sensors, and GPS receivers.
It has been defined and is controlled by the US based National Marine Electronics Association (NMEA). Information on their official web site (http://www.nmea.org) is somewhat sparse. Another web site, http://www.jackrabbitmarine.com, however, provides in-depth information.
NMEA 2000 is a modernized version and replacement of an older standard, NMEA 0183. It has a significantly higher data rate (250k bits/second vs. 4.8k bits/second for NMEA 0183). It also uses a binary message format as opposed to the ASCII serial communications protocol used by NMEA 0183. Another distinction between the two protocols is that NMEA 2000 is a multiple-talker, multiple-listener data network whereas NMEA 0183 is a single-talker, multiple-listener serial communications protocol.
