Pll; Lpn Pll; Gps Primary Receiver And Gps Secondary Receiver - Symmetricom XLi User Manual

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• Investigate the reference sources. Determine whether they are "Locked" or "Unlocked" and whether
they are "Primary", "Secondary", or "Standby". For Aux Ref, which doesn't have Primary/Secondary
setting, check F113. For GPS, check F119. For IRIG, use F110. For Have Quick/PPS, use F123. For
further guidance, read the Function Reference section for each function in this User Guide.
• Investigate F74, which determines how the XLi switches between Primary and Secondary reference
sources. For further guidance, read the Function Reference section for F74 in this User Guide.
• Even though the Aux Ref input is a reference source, it is not treated as a Primary or Secondary ref-
erence source by the XLi. If Aux Ref is available, the XLi clock uses it in place of its internal oscillator
while no reference source is available.

PLL

Status: Locked or Unlocked
The PLL indicator reports "Locked" during normal operation while the system clock's PLL is locked to the
internal oscillator.
The PLL indicator reports "Unlocked" if the XLi clock's hardware PLL has failed. While the PLL indicator
is "Unlocked", all XLi clock timing parameters are unreliable and should not be used. Contact Symmetri-
com Global Customer Assistance.

LPN PLL

Status: Locked or Unlocked
The LPN (Low Phase Noise) PLL indicator reports "Locked" during normal operation while the LPN oscil-
lator on an LPN Card is locked to the XLi's internal oscillator.
The LPN PLL indicator reports "Unlocked" for several minutes after the unit is started while the LPN
oscillator on the card warms up. This is not a significant error, and if needed, can be prevented by
extending the duration of the Power-On Alarm Suppress.
If the LPN PLL indicator reports "Unlocked" at any time other than the warm-up period, the LPN card's
PLL has failed or the LPN card's oscillator can no longer be steered to the internal XLi oscillator. All out-
puts from the LPN card are unreliable and should not be used. Contact Symmetricom Global Customer
Assistance.
When multiple LPN cards are present, an LPN PLL fault on any one of the LPN cards will change the
LPN PLL indicator to "Unlocked". If so, all LPN card outputs should be considered unreliable and should
not be used until the faulty card has been identified. All other outputs, unless in an alarm condition, con-
tinue to be available for use. Contact Symmetricom Global Customer Assistance.

GPS Primary Receiver and GPS Secondary Receiver

Status: OK or Fault
GPS Primary Receiver and GPS Secondary Receiver indicators report "OK" when the corresponding
GPS receiver card is tracking satellites, has a valid position, and is providing time to the clock without
faults. They report "Fault" if any of the preceding conditions aren't met. This can be due to poor visibility
of the GPS satellites, a failed antenna, an open or shorted antenna cable, or a failed GPS receiver card.
XLi Time & Frequency System
XLi-man, Issue 8, 6/17/2008, Rev. H
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
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