Page 130 of 188 NTD12 Dual-port DTI/PRI card description and installation
553-2901-200 Standard 11.00 August 1996
Automatic clock switching
If the EREF command is selected in Overlay 60, tracking on the primary or
secondary reference clock is automatically switched in the following manner:
— 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.
Clocking configurations
Clock Controllers may be used in a single CPU system or a dual CPU system.
A single CPU system has one Clock Controller card. This card can receive
references clocks from two sources referred to as the primary and secondary
sources. These two sources can originate from a PRI, DTI, etc. PRI cards such
as the QPC720 are capable of supplying two references of the same clock
source. These are known as Ref1 (available at J1) and Ref2 (available at J2)
on the QPC720.
The NT5D12 card is capable of supplying two references from each clock
source, i.e., four references in total. NT5D12 can thus supply Clk0 and Clk1
from Port 0 and Clk0 and Clk1 from Port 1. Either Port 0 or Port 1 can
originate primary source, as shown in
.
There is one new Clock Controller cable required for the new DDP card,
which is available in four sizes; this is the NTCG03AA/AB/AC/AD. Refer to
“Reference clock cables” on page 121
for more information.
summarizes the clocking options.
more detail.
