5: Function Reference
The GPS receiver serves as a UTC time reference for the XL-GPS system clock. To be a
valid time reference, the receiver requires the following information:
•
The GPS time (at least one “good current” GPS satellite)
•
The current position of the receiver
•
The UTC leap-second offset
Following power-up and initialization, the receiver requires at least four concurrent “good
current” satellites () to resolve its current position. In rare cases, when a pair of “good
current” satellites are on intersecting paths, the receiver requires additional “good current”
satellites or waits for the intersecting satellites to diverge before resolving the current
position. Once resolved, the current position information is saved.
For additional information on GPS position information,
see “F50 – GPS Receiver LLA/XYZ
Position” on page 72
.
While resolving its current position, the GPS receiver also listens for the
UTC leap-second
offs
et periodically transmitted by GPS satellites along with GPS time and position
information. Up to thirteen minutes may elapse from the time the receiver acquires its
first
“good current” satellite to the time it receives the UTC leap-second offset. Once received, the
UTC leap-second offset is saved.
When the receiver has
the current position
,
the UTC leap-second value
,
and
the current
GPS time
, it starts providing valid time to the XL-GPS system clock. When the system clock
is locked to the GPS time reference and is operating within specifications, the system status
is locked. The interval from initialization to system status lock is typically under twenty
minutes, under nominal conditions. This transition is illustrated below.
Following initialization, the front panel display of an XL-GPS with a GPS receiver (GPS
Status: Unlocked) would show the following:
UNLOCKED * GPS
LOCAL 365:16:01:05 1969
With the GPS receiver as a valid time reference, the following changes would take place:
•
The asterisk (“*”) indicating the absence of a valid reference would disappear
•
The system status would change to locked
The front panel status display would look like this:
LOCKED GPS
LOCAL 233:18:21:29 2005
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098-00116-000 Rev. A
Содержание XL-GPS
Страница 1: ...XL GPS Time Frequency Receiver User Guide CD Part Number 098 00116 000 Rev A 5 May 2010 ...
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Страница 38: ...3 Installation Configuration Figure 2 GPS Signal Strength Requirements Page 24 of 221 098 00116 000 Rev A ...
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Страница 162: ...5 Function Reference For example enter F119 C PRI CR XL GPS responds OK CR LF Page 148 of 221 098 00116 000 Rev A ...
Страница 184: ...7 XL GPS Generated Messages This page has been intentionally left blank Page 170 of 221 098 00116 000 Rev A ...
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Страница 214: ...IRIG IRIG Standard Format A 098 00116 000 Rev A Page 200 of 221 ...
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Страница 216: ...F World Map of Time Zones 098 00116 000 Rev A Page 202 of 221 ...
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Страница 220: ...I Certificate of Volatility See the following document 098 00116 000 Rev A Page 206 of 221 ...
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Страница 225: ...J Declaration of Conformity See the following document 098 00116 000 Rev A Page 208 of 221 ...