Nortel Circuit Card, Руководство по установке, Страница: 37 / 908

Overview Page 37 of 906
Circuit Card Description and Installation
A card LAN link bus is common to all of the line/trunk card slots within an
IPE module. This bus is arranged in a master/slave configuration where the
controller card is the master and all other cards are slaves. The module
backplane provides each line/trunk card slot with a unique hardwired slot
address. This slot address enables a slave card to respond when addressed by
the controller card. The controller card communicates with only one slave at
a time.
In normal operation, the controller card continually scans (polls) all of the
slave cards connected to the card LAN to monitor their presence and
operational status. The slave card sends replies to the controller on the input
bus along with its card slot address for identification. In its reply, the slave
informs the controller if any change in card status has taken place. The
controller can then prompt the slave for specific information. Slaves only
respond when prompted by the controller; they do not initiate exchange of
control or status data on their own.
When an IPE line card is first plugged into the backplane, it runs a self-test.
When the self-test is completed, a properly functioning card responds to the
next controller card poll with the self-test status. The controller then queries
for card identification and other status information. The controller then
downloads all applicable configuration data to the line card, initializes it, and
puts it into an operational mode.
Analog line interface units
Once the 8-bit digital voice signal has been received by the analog line card,
it must be converted back into an analog signal, filtered, converted from a
4-wire transmission path to a 2-wire transmission path, and driven onto the
analog telephone line.
Figure 4 on page 38 shows a typical example of the logic that performs these
functions. Each part of the analog line interface unit is discussed in the
following section.