Nortel Networks Circuit Card - Manual (Page 69)

Overview Page 69 of 906
Circuit Card Description and Installation
link is composed of two asynchronous serial buses (called the Async card
LAN link in Figure 11 on
page 64 ). The output bus is used by the controller
for output of control data to the trunk card. The input bus is used by the
controller for input of trunk card status data.
A card LAN link bus is common to all of the line/trunk card slots within an
IPE module (or IPE section of a CE 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 this 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 or trunk 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/
trunk card, initializes it, and puts it into an operational mode.
The network card regularly polls the IPE cards during TS0 to see if any of
them has a message to be sent. When an IPE card has a message waiting it
responds to the poll by sending a series of 1s during the next five successive
timeslot 0s. The network card responds by sending a “message send enable”
message (all 1s). The IPE card replies by sending 1, 1, 1, 0, and then the
message in successive timeslot 0s.
Trunk interface unit
Once the 8-bit digital voice signal has been received by the trunk card, it must
be converted back into an analog signal, filtered, and driven onto the analog