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Revision 1.2
Appendix A – NMEA 2000
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Interfacing
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Appendix A – NMEA 2000
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Interfacing
GPS200 NMEA 2000
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Periodic Data Transmitted PGNs
PGN 126992 – System Time
The GPS200 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 or the transmission rate of
this PGN can be changed (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 GPS200 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 GPS200 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 GPS200 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 or the transmission rate of this PGN can be changed (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 GPS200 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 GPS200 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 GPS200 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 129025 – Position, Rapid Update
