Symmetricom SDU-2000, User Manual

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Clock Module Reference Data
Stratum 3E Clock Module
128 SSU-2000 User’s Guide 12713020-002-2 Revision D – April 2004
Stratum 3E Clock Module
This section provides user reference information for the Stratum 3E Clock module
(part number 23413015-000-0) used in the SSU-2000. This module provides a
lower cost backup clock solution for the system.
Functional Overview
The Stratum 3E Clock module meets or exceeds the performance requirements for
ITU and ETSI Type III Local Node clocks and ANSI and Telcordia Technologies
(Bellcore) Stratum 3E clocks.
The Stratum 3E Clock module receives measurement data from the Input modules,
provides frequency control of the outputs through DDS circuitry, and generates a
reference signal for use by the Input and Output modules. The Stratum 3E Clock
module communicates with the Communications module and the Stratum 2E Clock
module to maintain phase synchronization with the redundant Clock module. The
Stratum 3E Clock module’s hardware and software provides for temperature
compensation, aging compensation for the Quartz oscillator, an initial offset
adjustment, and frequency adjustment resolution of 1 x 10
-13
or better.
When serving as the master clock, the Stratum 3E Clock module controls the
operation of the Input and Output modules and downloads module configuration
information to all modules, requests measurement data and status from the Input
modules, and sets the Output modules to use currently selected Clock signals. The
Stratum 3E Clock module also contains a battery powered clock that maintains the
clock for timestamping events. The Clock module software reads the clock on
startup and sets the clock when the system time is changed. The timestamp is
referenced as the number of seconds since 00:00:00 January 1, 1980.