Symmetricom XLi IEEE 1588 User Manual

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The standard XLi IEEE 1588 Clock, also referred to as the “XLi”, provides a complete implementation of 
a Precise Time Protocol (PTP) “ordinary clock” over a dedicated IEEE 1588 card. The IEEE 1588 card 
can be configured to operate as a PTP grandmaster or as a PTP slave. 

As a PTP grandmaster, the IEEE 1588 card typically synchronizes PTP slaves on the network to 
International Atomic Time (TAI). The XLi IEEE 1588 Clock derives TAI from the Global Positioning 
System (GPS). In addition, Symmetricom designed the XLi IEEE 1588 Clock so the user can distribute 
Coordinated Universal Time (UTC) or user-entered time over PTP. 

As a PTP slave, the IEEE card automatically discovers a PTP master within its subnet/subdomain and 
synchronizes to it. The PTP slave in turn, can be configured as the primary reference source for the XLi 
IEEE 1588 Clock (the clock synchronizes to the PTP slave). 

The XLi’s Time Interval/Event Time (TIET) feature can be used to measure PTP synchronization across 
timing networks. For example, to measure a PTP slave’s synchronization to the PTP grandmaster, the 
user connects the PPS output of a PTP slave to the XLi IEEE 1588 Clock and configures F110 to display 
the time interval between each PPS. 

 for more information.

The XLi IEEE 1588 Clock can be purchased in two configurations. The first configuration includes one 
IEEE 1588 card preconfigured as a PTP master and located in Option Bay 4. The second configuration 
has an additional IEEE 1588 card preconfigured as a PTP slave located in Option Bay 2. Both 
configurations include the following items.

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XLi chassis and CPU card running special firmware

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The IEEE 1588 card(s)

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L1 GPS Antenna

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GPS antenna cable: 50 ft. (15.24 m) of RG-59

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Time Interval Event Time (TIET)

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1. Other GPS antenna cable lengths can be specified at the time of purchase.