Clock Controller Interface - Nortel Enterprise 1000 Reference Manual

Clock controller interface

The clock controller circuitry on the NTAK79 is identical to that of the
NTAK20 clock controller.
Though several DTI/PRI packs can exist in one system, only one clock
controller may be activated. All other DTI/PRI clock controllers must be
switched off.
Clocking modes
The clock controller can operate in one of two modes:
• tracking
• non-tracking (also known as free-run).
For more information on clocking modes, see page 152
Clock controller functions and features
The NTAK79 clock controller functions and features include:
• phase lock to a reference, generate the 10.24 MHz system clock, and
distribute it to the CPU through the backplane. Up to two references at a
time are accepted.
• provide primary to secondary switchover (auto-recovery is provided)
• prevent chatter
• provide error burst detection and correction, holdover, and free running
capabilities
• comply with 2.0Mb CCITT specifications
• communicate with software
• provide jitter filtering
• make use of an algorithm to aid in detecting crystal aging and to qualify
clocking information
Reference switchover
See "Reference switchover" on page 30.
Succession Communication Server for Enterprise 1000 Circuit Card Reference Guide
NTAK79 2.0 Mb PRI card Page 179 of 236