Operation 27
Operation
general commands cause the G12 to return the $PASHR,NAK*30 “not
acknowledged” response message.
G12 Message Output
The G12 can be programmed to send data to another device. Output messages
include general receiver status messages, ACK/NAK messages, and GPS data
messages. The general receiver status messages have free-form Ashtech
proprietary formats. The acknowledged/not acknowledged messages and GPS
data messages comply with NMEA 0183 standards as follows:
• NMEA ASCII byte strings following a dollar sign ($) character
• Headers are standard NMEA or Ashtech proprietary NMEA
• Message IDs are standard NMEA or Ashtech proprietary NMEA
• Standard NMEA format messages contain hexadecimal checksum bytes
• Data items are separated by commas; successive commas indicate invalid
or missing data (null fields)
• Messages end with [CRLF] (carriage return/line feed), the standard NMEA
message terminator characters
The G12 receiver has two RS-232 serial ports that support two-way, full-duplex
communication. The default protocol for transmitting or receiving data is 9600
baud, eight data bits, no parity, and one stop bit (8N1). The baud rate of the G12
ports is adjustable using the $PASHS,SPD speed set command; the data bit, stop
bit and parity protocol is always 8N1.
On initial power-up, or after issuing the $PASHS,INI (receiver initialization)
command or the $PASHS,RST (restore defaults) command, the default data rate
is 9600 baud for both G12 serial ports.
The baud rates must be the same between the G12 serial port and the serial port
on the device with which it is interfaced.
DEFAULT SETTINGS
The default parameters for the G12 serial ports:
•Baud Rate— 9600
•Data Bits— 8
•Stop Bits— 1
•Parity— None
G12RevD.book Page 27 Tuesday, April 2, 2002 4:33 PM
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