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Commands
Using the symbols from Table 4.1, the general format for the set commands used
to control the NMEA message output is as follows:
$PASHS,NME,s1,c2,s3,[f4]
In this context, set commands are used to enable the output of NMEA messages
at regular intervals or to disable message output, where s1 is a three character
message identifier (GGA, VTG, SAT, etc.). c1 is the port designator (A or B) for
message output. s3 is ON or OFF. f4 is the optional message output rate ranging
from 0.05 to 999 seconds depending on the measurement update rate option
installed.
If the command is set without a period, the G12 uses the period set by the
$PASHS,NME,PER command If the $PASHS,NME,PER command is issued after
this message period has been set, the period resets to the PER setting.
Before using the 10 Hz or 20 Hz update rate, you must issue the $PASHS,POP command.
Query commands prompt the receiver to output the corresponding response
message once only. Message output prompted by a query command occurs
independently of any related message output settings.
To enable the output of the POS message on port A at five second intervals, enter
the following command:
$PASHS,NME,POS,A,ON,5
To disable the output of the GGA message on port B, enter the following command:
$PASHS,NME,GGA,B,OFF
To query for the POS message and designate port B for the output of the response
message, enter the following command:
$PASHQ,POS,[B]
As with the other query commands, the port designator (B) is optional. If a port is
not specified, the receiver sends the response to the current port.
Message Structure
Standard NMEA messages are output as a string of ASCII characters delimited by
commas, in compliance with NMEA 0183 Standards (version 2.1). Ashtech’s
NMEA-style messages are also output in a comma-delimited string of ASCII
characters, but may deviate slightly from NMEA standards. For example, the
maximum length of a standard NMEA message is eighty characters, but the length
of some Ashtech messages are variable (i.e., SAT) and may go beyond eighty
characters. Both NMEA messages and Ashtech NMEA-style messages begin with
a dollar sign ($) and end with a Carriage Return/Line Feed <CR><LF> delimiter.
G12RevD.book Page 141 Tuesday, April 2, 2002 4:33 PM
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