Motorola M12 Oncore User's Guide download pdf (Page 38)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

NMEA 0183 Format

Overview

(Continued)

For the case where more than one output message is scheduled during the same

one second interval, the GPS receiver will output all scheduled messages but will

attempt to limit the number of bytes transmitted each second to 400 bytes. For the

case of multiple output messages, if the next message to be sent fits into the 400 byte

length goal, then the message will be output. For example, if messages totaling 334

bytes are scheduled to be sent, and the user requests another 80 byte message, then

414 bytes will actually be sent. If the user requests yet another 70 byte message, then

its output will not be generated. The order for priority for transmitting messages is

simply alphabetical.

The NMEA input and output are on the primary serial port. For details on the

command formats see the Input/Output section of this document.

RTCM SC104 Format

Overview

RTCM Differential GPS Support

The M12+ and GT+ Oncore 2.x firmware supports the RTCM SC-104 format for

differential corrections. The receiver employs a decoding algorithm that allows the

unit to directly decode the RTCM Type 1 and Type 9 (6 of 8 type with two most

significant bits always 01) differential correction messages from the secondary input

serial port (pin 5). Having a separate port allows the M12+ and GT+ Oncore to

simultaneously accept the RTCM format data stream and other receiver input

commands (in either Motorola binary format or in NMEA format).

Revision 5.0 08/30/02

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Motorola M12 Oncore User's Guide Page 38