Maintenance - Symmetricom XLi User Manual

S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S
One of the two broadcast bytes gives the indication that the XLi is operating properly and within its
specifications for time and frequency accuracy and stability. The other broadcast byte provides direct
indication of major and minor alarm status of the XLi. The logic in the FPGA combines the line fault
signals and the broadcast byte inputs to form a summary major alarm indication. The FPGA uses the
1
broadcast byte minor alarm information verbatim to control minor alarm indication. In addition, if position
8 of S1 is in the OFF position, then the FPGA will cause U8 and U9 to transmit the AIS pattern and will
turn off the optional output signals whenever a major alarm occurs.
The FPGA also implements a "watchdog" function by requiring that the broadcast bytes are in fact
broadcast once a second. Should they not arrive on time, then the FPGA would assert a major alarm.
This assures that failure of the main XLi processor would be detected.

Maintenance

This card is maintenance-free.
186 XLi Time & Frequency System
XLi-man, Issue 8, 6/17/2008, Rev. H
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