Symmetricom SDU-2000, User Manual

Page: 132 / 470

Clock Module Reference Data
Type 1 Clock Module
132 SSU-2000 User’s Guide 12713020-002-2 Revision D – April 2004
Type 1 Clock Module
This section provides operating instructions and software provisioning procedures
for the Type 1 Clock module (part number 23413015-001-0), designed for use in the
SSU-2000 Synchronization Supply Unit.
Functional Overview
The Type 1 Clock module uses a quartz oscillator which meets or exceeds the
performance requirements for ITU and ETSI Type 1 Slave clocks. The Clock
module reads measurement data from the Input modules, provides frequency
control of the oscillator through DDS circuitry, and generates reference signals used
by the Input and Output modules.
A typical SSU-2000 shelf contains dual redundant Clock modules. Each Clock
module maintains phase synchronization with the redundant Clock module. Its
hardware and software also provides an initial offset adjustment and frequency
adjustment resolution of 1 x 10
-13
or better.
With redundant Clock modules, one is selected as the master and the other as
backup, with automatic switching on module removal or failure.
The master Clock module controls the operation of the Input and Output modules
and downloads module configuration information to all modules (except for the
Communications module), requests measurement data and status from the Input
modules, and sets the Output modules to use currently selected clock signals, and
provides the system Priority Quality Level (PQL) to all Output modules configured to
generate Synchronization Status Messages (SSMs). The Clock modules maintain
an internal time-of-day clock that is used to time stamp events to within 0.1 second
of detection of the event.
This module provides an 8 kHz signal used by the Input modules and a 4 kHz signal
used by the Output modules. Each Clock module provides one set of signals for use
by the modules in the main chassis, and a separate set for the expansion shelves.