Clock Section - Symmetricom SSU-2000e User Manual

Chapter 1 Product Overview
System Architecture

Clock Section

The clock section consists of one or two Clock modules that provide the internal
reference signals for generating TSG output timing signals. The primary Clock
module (Clock A) is configured as the master clock and is normally a higher stratum
level than the back-up clock (Clock B). If a problem occurs in Clock A, the control is
automatically passed to the back-up clock module (Clock B). The frequency of each
clock is locked to a valid reference input signal (one that is free from input faults
while meeting acceptable frequency and MTIE specifications).
The SSU-2000e controls clock frequency by adjusting the control value of the Direct
Digital Synthesis (DDS) function in each Clock module. The adjustments are
processor-controlled and based on measurements performed and computed in the
input module(s). Internal clock modules may be Stratum 2E, Stratum 3E, and
Type I. Outputs are maintained by the active input reference signal if both clocks
should ever fail or be removed from the system.
Communications Section
The Communications section consists of one Communications module, which
contains hardware and software that allows the user to configure, monitor, and
control the SSU-2000e system and generate local and remote alarms when fault
conditions are detected. The SSU-2000e can continue to function seamlessly
without the Communications module (Clock modules assume the system controller
function), but all communications and alarm reporting functions are interrupted.
The master controller function for the SSU-2000e can reside in either the
Communications module or in either of the Clock modules. The priority of the
selection of the module that will provide the master controller function rests with the
Communications module, Clock A, and Clock B, in that order. In the event of
removal of the module designated as the master controller, that function
automatically and seamlessly switches to the next module in priority order.
The Communications module communicates with the other modules in the
SSU-2000e to read configuration data, set operational parameters, and determine
what type of modules are installed. When a module is replaced, the controller loads
the correct operational parameters into the replacement module.
The Communications module is installed in slot A2 and provides an interface
between the user and the SSU-2000e system. This interface allows the user to
display and control much of the activity in the SSU-2000e system and within the
optional SDU-2000e expansion system. The Communications module supports
three serial ports and one Ethernet port, and allows communication over each of
them independently in one of several possible modes (ICS, TL1, SNMP, or packet).
The software in the Communications module allows for on-site reprogramming of
the flash ROM and all programmable logic devices. The software on all other
module types installed in the SSU-2000e system can be updated by downloading it
through the Communications module.
28 SSU-2000e User's Guide 12713140-002-2 Revision E – October 2006