Motorola M12 Oncore User's Guide download pdf (Page 37)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

Motorola Binary

Format Input/Output

Processing Time

NMEA Support

The GT Oncore 2.x firmware supports the NMEA 0183 format for GPS data output.

Output of data in the NMEA-0183 standard format allows a direct interface via the

serial port to an electronic navigation instrument that supports the specific output

messages. The following NMEA output messages are supported as per the NMEA-

0183 Specification Revision 2.0.1.

Message Description

GPGGA GPS Fix Data

GPGLL Geographic Position Latitude/Longitude

GPGSA GPS DOP and Active Satellites

GPGSV GPS Satellites in View

GPRMC Recommended Minimum Specific GPS/Transit Data

GPVTG Track Made Good and Ground Speed

GPZDA Time and Date

You can enable or disable each message output independently and control the

update rate at which the information is output. If back-up battery power is applied or

if the receiver has the battery option, then the GT Oncore receiver retains the output

settings when powered off and reconfigures itself to the same state when powered

up again. If no back-up power is provided, the receiver will start up in the default

state (Motorola binary format at 9600 baud) each time it is powered on.

All NMEA messages are formatted in sentences that begin with the ASCII $ (hex 24)

and end with ASCII <CR><LF> (hex OD and hex OA). A five character address occurs

after the ASCII $. The first two characters are the talker ID (which is GP for GPS

equipment), and the last three characters are the sentence formatter or message ID

from the list above. Note that the NMEA messages are not fixed length. Fields within

the message are delimited by the ASCII comma character. The maximum length of

any NMEA message is 79 characters.

The checksum is calculated by XORing the 8 data bits of each character in the

sentence between, but not including, the $ and the optional (*) or checksum (CS). The

high and low nibbles of the checksum byte are sent as ASCII characters.

The output of the above listed messages is controlled with a Motorola NMEA format

message. Input messages follow the NMEA specification, and take the form

$PMOTG,,,,,*CS<CR><LF>. All input parameters are separated with comma delimiters.

The P character identifies the message as Proprietary format, the MOT is the

manufacturer designator for Motorola, and the G is for GPS.

Revision 5.0 08/30/02

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Motorola M12 Oncore User's Guide Page 37