135
Commands
The G12 is designed to synchronize raw message output with the hour rollover, so that message
output from multiple receivers can be synchronized regardless of when they were turned on. An
output interval of 0.7 is not allowed because it overlaps the hour rollover, which corrupts
synchronization between multiple receivers.
Almanac data for all satellites is output once every hour, with one almanac message output for each
satellite in the constellation. The almanac messages are output at interval prescribed by the
$PASHS,RCI command.
At the 10 Hz output rate (0.1 seconds), a baud rate of 115,000 bps is required to output all the raw
data (MBN, PBN, SNV, and SAL). For greater output rates, the raw data must be split between the
two serial ports, or some of the messages should be turned off. To receive data at high baud rates
(e.g., 115,000), you must ensure that your computer has a suitable serial I/O capability. Most newer
computers with Pentium or 486 processors have good enough serial communication to support
high data rates.
SAL: Satellite Almanac Data
$PASHQ,SAL,[c1]
This command allows you to query for satellite almanac data.
c1 is the optional port designator for the response. If a port is not specified, the
receiver sends the response to the current port.
$PASHR,SAL
This message is not output until the G12 has completed downloading the current
GPS almanac file. The receiver begins downloading the almanac file automatically
almanac file can be obtained directly from the satellites, which happens
automatically and takes about twelve minutes, or, with the aid of software, a current
almanac file from another receiver can be manually downloaded into the G12. A
separate almanac message is output for each satellite being tracked. The SAL
message contains information on satellite health, the almanac week number, and
a variety of orbital measurements. The response is output in the format:
$PASHR,SAL,<Satellite almanac data string + checksum>
DEFAULT SETTING
RCI 20
G12RevD.book Page 135 Tuesday, April 2, 2002 4:33 PM
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