Table of Contents
Advertisement
13 — System timing and timing sources
13.1
System timing
The various clock rates required for system timing are provided by the system
synchronization unit, which is located on the Control card. The timing source that
drives the SSU is user-configurable.
System timing can be set for:
•
standalone (STANDALONE)
•
automatic network synchronization (AUTO_SYNC)
The default is standalone system timing.
Standalone
Typically, standalone system timing is used when a 2902 MainStreet system is used
in a single-ended or point-to-point application. When operating in standalone mode,
the system uses only those timing sources that have been configured locally.
Automatic network synchronization
ANS is used when the 2902 MainStreet system is part of a network. In this case, each
node has access to all timing sources in the network. This allows every node to
receive timing signals from the same source, ensuring network synchronization. In
addition, ANS allows you to divide a network into sectors where each sector has
independent timing.
Procedure 13-1 Standalone configuration summary
1
2
13-2
Note — When the method of synchronization is changed (standalone to
ANS, or ANS to standalone), timing sources are reset to their default
clock and recovery configurations (free-run and manual recovery).
Enable standalone system timing on the node (see Procedure 13-3).
The STANDALONE and AUTO_SYNC softkeys only appear when all
synchronization sources have a status of disabled, undefined or unavailable. To
disable a timing source, see section 13.2.
Configure the timing sources that can provide timing for the node.
Timing source configuration parameters are described in section 13.2, and include
setting the class number, failure threshold and recovery method. See sections 13.3
to 13.6.
2902 MainStreet Technical Practices
90-2906-01
May 2002
Advertisement
Table of Contents
