Motorola M12 Oncore User's Guide download pdf (Page 46)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

Output Data Timing Relative to Measurement Epoch (Continued)

The Position/Status/Data Message and the

Time RAIM Setup and Status Message are the only output messages containing time

information. If enabled, these messages will be output from the receiver shortly after

a measurement epoch. Generally, the first data byte in the first message will be

output between 0 to 50 ms after a measurement epoch. For the Position/Status/Data

Message, the time output in the message reflects the best estimate of the most

recent measurement epoch. A simple timing diagram is shown in figure 3.12.

IPPS Cable Delay and IPPS Offset (UT Model Only)

1PPS Cable Delay and 1PPS OfFset (M12 Timing and UT Model

Only)

Users can compensate for antenna cable length with the 1PPS Cable Delay

command. The IPPS can also be positioned anywhere in the one second window

using the 1PPS Offset command. The rising edge of the IPPS is placed so that it

corresponds to the time indicated by the following equation:

1PPS rising edge time = top of second -1PPS cable delay + 1PPS offset

Consider the following example:

Top of second = 10.000000000 s

1PPS cable delay = 0.000654321 s

1PPS offset = 0.100000000 s

1PPS rising edge time = 10.099345679 s

The rising edge of the IPPS signal is adjusted so that it occurs corresponding to the

fractional part of time equal to the total above. The fractional part of time is measured

relative to UTC or GPS time depending on the setting of the Time Mode.

Revision 5.0 08/30/02

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Motorola M12 Oncore User's Guide Page 46