Motorola M12 Oncore User's Guide download pdf (Page 49)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

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In order to handle the 1999 rollover, Motorola GT and UT Oncore GPS receivers use a

ROLLOVERS I

In August of 1999, the GPS week number will rollover from 1023 to 0 due to the l

length of the GPS week field in the navigation data stream. Motorola Oncore

receivers (M12+, M12 Timing, GT+, UT+, VP, XT, and Basic) have been designed and

tested to properly distinguish the correct 20 year window (1024 weeks is just shy o

years). They will not need reprogramming or replacement come 1999. In fact, the

transition will be completely transparent to users of Motorola Oncore GPS receivers

Motorola Oncore GPS receivers are also year 2000 compliant.

Multichannel GPS satellite simulators have been used to test each rollover condition

in GPS. For example, each week there is a rollover in the GPS seconds on midnight

Saturday. The August 1999, year 2000, leap day, and leap second rollovers have a

been successfully tested using simulators.

date stored in flash memory. For example, if the firmware date is 1998, a defaulted

receiver that does not have back-up power (or battery) will start with an internal tim

of 12:00 on 1/1/98 and begin acquiring satellites. Once the first satellite is acquired,

the time and week number will be downloaded from the navigation data message

The receiver determines the current date by starting from the week number of 1/1/98

(week 938) and searching for the first occurrence of the current week number (week

964 for 7/1/98).

Revision 5.0 08/30/02

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Motorola M12 Oncore User's Guide Page 49