Next bit is the data page -selector (DP). Next bit (R) is reserved for the future and should therefore be set to zero. Time-critical control messages (like engine control) usually get a high priority whereas less critical messages (such as speed) get a lower priority. Structure of the 29-bit ID, PGN marked with blue colorįirst three bits (PRIO) specify the priority of the message, zero being the highest priority. NMEA 2000 message structureĪ 29-bit ID is used in NMEA 2000 (J1939) and the structure is as follows PRIORITY (PRIO) Raymarine SeaTalk 2, Raymarine SeaTalk NG, Simrad Simnet and Furuno CAN are rebranded NMEA 2000 networks, but use a different physical connector than the standard DeviceNet Micro-C M12 connector. Because of this, no request-type messages are needed. Majority of NMEA 2000 and J1939 messages are of a broadcast-type with no destination address specified. This makes NMEA 2000 a plug-and-play -type network. The biggest difference between J1939 and NMEA 2000, in addition to the marine-specific messages, is that in J1939 the device and sensor IDs are hard-coded whereas in NMEA 2000, the addresses are negotiated when a new device joins the network. NMEA 2000 protocol is based on SAE J1939, which has been expanded by marine-specific messages. Electrically NMEA 2000 is compatible with Controller Area Network (“CAN bus”), which is used in gasoline and diesel powered (road) vehicles.

The speed of the NMEA 2000 bus is 250 kbit/s and it enables sensors and displays and any other NMEA 2000 compatible devices to “discuss” together. NMEA 2000 (standardized as IEC 61162-3), abbreviated NMEA2k or N2K, is a plug-and-play communications standard, which is used on boats and ships to connect together devices, displays and sensors.

Nmea 2000 network devices