Nortel Networks 311 Reference clock errors, Automatic clock recovery, Automatic clock switching

352 NT5D97 Dual-port DTI2 PRI2 card

Reference clock errors

CS 1000 software checks at intervals of 1 to 15 minutesto see if a clock

controller or reference-clock error has occurred. (The interval of this check

can be conﬁgured in LD 73).

In tracking mode, at anyone time, there is one active clock controller which

is tracking on one referenceclock. If a clock controller error is detected, the

system switches to the back-up clock controller, without affectingwhich

reference clock is being tracked.

A reference-clockerror occurs when there is a problem with the clock driver

or with the reference clock at the far end. If the clock controller detects a

reference-clock error,the reference clocks are switched.

Automatic clock recovery

A command for automatic clock recovery can be selected in LD 60 with

the command EREF.

A DDP2 loop is disabled when it enters a local-alarm condition. If the local

alarm is cleared, the loop is enabled automatically. When the loop is

enabled, clock tracking is restored in the followingconditions:

•If the loop is assigned as the primary reference clock but the clock

controller is tracking on the secondary reference or in free-run mode, it

is restored to tracking on primary.

•If the loop is assigned as the secondary reference clock but the clock

controller is in free-run mode, it is restored to tracking on secondary.

•If the clock check indicates the switch is in free-run mode:

— Trackingis restored to the primar y referenceclock if deﬁned.

— If the primary reference is disabled or in local alarm, tracking is

restored to the secondary reference clock if deﬁned.

Note: If the system is put into free-run mode by the craftsperson,

it resumes tracking on a reference clock unless the clock-switching

option is disabled (LD 60, command MREF), or the reference clock

is "undeﬁned" in the database.

Automatic clock switching

If the EREF command is selected in LD 60, tracking on the primary or

secondary reference clock is automatically switched in the followingmanner :

•If software is unable to track on the assigned primary reference clock, it

switches to the secondary reference clock and sends appropriate DTC

maintenance messages.

•If software is unable to track on the assigned secondary reference clock,

it switches to free run.

Nortel Communication Server 1000

Circuit Card Reference

NN43001-311 01.04 Standard

Release 5.0 23 May 2008