Motorola M12 Oncore User's Guide download pdf (Page 45)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

The computed time is relative to UTC or GPS time depending on the time type as

specified by the user by the Time Mode.

The Oncore system timing is designed to slip time when necessary in discrete one

millisecond intervals so that the receiver local time corresponds closely to the

measurement epoch offset. The Oncore observes the error between actual receiver

local time and the desired measurement epoch offset and then slips the appropriate

integer milliseconds to place the measurement epoch to the correct integer

millisecond. When a time skew occurs (such as after initial acquisition or to keep

time within limits due to local oscillator drift), the receiver lengthens or shortens the

next processing period in discrete one millisecond steps.

The rising edge of the 1PPS signal is the time reference. The falling edge will occur

approximately 200 ms (+/-1 ms) after the rising edge. The falling edge should not be

used for accurate time keeping.

Output Data Timing Relative To Measurement Epoch

Figure 3.12: Output Signal Timing

Revision 5.0 08/30/02

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Motorola M12 Oncore User's Guide Page 45