NMEA-TP (IEC 61162-3)

NMEA-2000 is based on J1939 and thus includes the specification of J1939 transport protocol. In addition, NMEA-2000 adds an alternative transport method called fast-packets[1].

The following is supported:

• Transmissions up to the maximum 223 data bytes

• Segmentation with and without padding

A simplified interpretation of the NMEA fast-packet frames are provided below.

First frame (6 data bytes)

BYTE 0 (7-5)	BYTE 0 (4-0)	BYTE 1	BYTE 2-7
Session no.	Sequence no.	Nob	DATA

Consecutive frame (7 data bytes)

BYTE 0 (7-5)	BYTE 0 (4-0)	BYTE 1-7
Session no.	Sequence no.	DATA

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[1]

The motivation for fast-packets is likely to reduce the overhead introduced by the J1939-21/22 transport-protocols.