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Revision 1.2 Appendix A – NMEA 2000
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Interfacing Page A1
Appendix A – NMEA 2000
®
Interfacing
GPS100 NMEA 2000
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Periodic Data Transmitted PGNs
PGN 126992 – System Time
The GPS100 uses this PGN to provide a regular transmission of UTC time and date and to
provide synchronism for measurement data. The factory default for periodic transmission rate
is once per second. The transmission of this PGN can be disabled (see PGN 126208 – NMEA
Request Group Function – Transmission Periodic Rate).
Field 1: SID – The sequence identifier field is used to tie related PGNs together. For
example, the GPS100 will transmit identical SIDs for 126992 (System Time), 128259
(Speed), 129026 (COG and SOG, Rapid Update), 129029 (GNSS Position Data),
129539 (GNSS DOPs), and 129540 (GNSS Satellites in View) to indicate that the
readings are linked together (i.e., the data from each PGN was taken at the same
time although they are reported at slightly different times).
2: Source – This field is used to indicate the type of time source, therefore this field
always reads as 0 (GPS).
3: Reserved (4 bits) – This field is reserved by NMEA; therefore, this field always
contains a value of 0xF (the GPS100 sets all reserved bits to a logic 1)
4: Date – This field is used to indicate the UTC Date in resolution of 1 day (the number
of days since January 1, 1970).
5: Time – This field is used to indicate the UTC Time in resolution of 1x10
-4
s (24 hour
clock, 0.0000 = midnight).
PGN 127258 – Magnetic Variation
The GPS100 uses this PGN to provide a regular transmission of magnetic variation. The
factory default for periodic transmission rate is once per second. The transmission of this PGN
can be disabled (see PGN 126208 – NMEA Request Group Function – Transmission Periodic
Rate).
Field 1: SID – The sequence identifier field is used to tie related PGNs together. For
example, the GPS100 will transmit identical SIDs for 126992 (System Time), 128259
(Speed), 129026 (COG and SOG, Rapid Update), 129029 (GNSS Position Data),
129539 (GNSS DOPs), and 129540 (GNSS Satellites in View) to indicate that the
readings are linked together (i.e., the data from each PGN was taken at the same
time although they are reported at slightly different times).
2: Variation Source – The GPS100 uses the WMM2005 for variation, therefore this field
always reads as 5 (WMM2005).
3: Reserved (4 bits) – This field is reserved by NMEA; therefore, this field always
contains a value of 0xF (the GPS100 sets all reserved bits to a logic 1)
4: Age of Service (Date) – This field is used to indicate the UTC Date in resolution of 1
day (the number of days since January 1, 1970).
5: Variation – This field is used to indicate the magnetic variation where positive values
represent Easterly and negative values represent Westerly variation.
PGN 128259 – Speed
The GPS100 uses this PGN to provide a regular transmission that describes the motion of a
vessel. The factory default for periodic transmission rate is disabled. The PGN can be