Jackson Labs LC_XO, Manual

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© 2012 Jackson Labs Technologies, Inc. 31
LC_XO GPSDO User Manual
Please note that the position, direction, and speed data is delayed by one second from when the GPS
receiver internally reported these to the LC_XO Microprocessor, so the position is valid for the 1PPS
pulse previous to the last 1PPS pulse at the time the data is sent (one second delay). The time and date
are properly output with correct UTC synchronization to the 1PPS pulse immediately prior to the
data being sent.
Once set, the following two commands will be stored in NV memory, and generate output
information even after power to the unit has been cycled.
4.3.5 GPS:GPGGA
This command instructs the LC_XO to send the NMEA standard string $GPGGA every N seconds,
with N in the interval [0,255]. The command is disabled during the initial 4 minute OCXO warmup
phase.
This command has the following format:
GPS:GPGGA <int> [0,255]
GPGGA shows height in MSL Meters, this is different from traditional GPS receivers that display
height in GPS Meters. The difference between MSL and GPS height can be significant, 35m or more
are common.
4.3.6 GPS:GGASTat
This command instructs the LC_XO to send a modified version of the NMEA standard string
$GPGGA every N seconds, with N in the interval [0,255]. The command is disabled during the initial
7 minute OCXO warmup phase.
This command has the following format:
GPS:GGASTat <int> [0,255]
This command replaces the regular NMEA GGA validity flag with a decimal number indicating the
lock-state of the unit. Please see section SERVo:TRACe for a detailed description of the lock state
variable. The command allows capture of the position and other information available in the GGA
command, as well as tracking the lock state and health of the unit’s OCXO performance.
GGASTat shows height in MSL Meters, this is different from traditional GPS receivers that display
height in GPS Meters. The difference between MSL and GPS height can be significant, 35m or more
are common.
4.3.7 GPS:GPRMC
This command instructs the LC_XO to send the NMEA standard string $GPRMC every N seconds,
with N in the interval [0,255]. The command is disabled during the initial 4 minute OCXO warmup
phase.
This command has the following format:
GPS:GPRMC <int> [0,255]