Nortel Networks 1000 - Manual (Page 798)

798 NTAK10 2.0 Mb DTI card
that it is within specifications. On failure (both out of specification), the
clock controller enters the HOLDOVER mode and continuously monitors
both references. An automatic switchover is initiated to the reference
that recovers first. If the primary recovers first, then the clock controller
tracks to the primary, but switches over to the secondary whenever
the secondary recovers. If the secondary recovers first, then the clock
controller tracks to the secondary.
A time-out mechanism prevents chatter due to repeated automatic
switching between primary and secondary reference sources.
If the software command "track to primary" is given, the clock controller
tracks to the primary reference and continuously monitors the quality
of both primary and secondary references. If the primary becomes
out of specification, the clock controller automatically tracks to
secondary provided that it is within specifications. On failure (both out
of specification), the clock controller enters the HOLDOVER mode and
continuously monitors both references. An automatic switchover is initiated
to the reference that recovers first. If the secondary recovers first, then the
clock controller tracks to the secondary, but switches over to the primary
whenever the primary recovers. If the primary recovers first, then the clock
controller tracks to the primary.
If the software command "track to secondary" is given, the clock controller
tracks to the secondary reference and continuously monitors the quality of
both primary and secondary references. If the secondary becomes out of
specification, the clock controller automatically tracks to primary provided
that it is within specifications. On failure (both out of specification), the
clock controller enters the HOLDOVER mode and continuously monitors
both references. An automatic switchover is initiated to the reference
that recovers first. If the primary recovers first, then the clock controller
tracks to the primary, but switches over to the secondary whenever
the secondary recovers. If the secondary recovers first, then the clock
controller tracks to the secondary.
A time-out mechanism prevents chatter due to repeated automatic
switching between primary and secondary reference sources.
See “Autorecovery and chatter” (page 815) .
Reference clock selection through software
The 2MB DTI card has the necessary hardware for routing its reference to
the appropriate line on the backplane.
Software is responsible for the distribution of the secondary references and
ensures that no contention is present on the REFCLK1 backplane line.
Software designates the 2MB DTI card as a primary reference source to
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 02.06 Standard
27 August 2008
Copyright © 2003-2008 Nortel Networks
.