Circuit Packs That Use The Packet Bus - Avaya MCC1 Maintenance Procedures

Packet and serial bus maintenance
S8100 packet bus fault isolation and repair
• Opens. An open occurs when there is a break on the packet bus such that the electrical path to
the termination resistors is broken. Usually, this break is caused by a failed TDM/LAN cable or
by a failed TDM/LAN terminator. The break can also be caused by a failure in the backplane of a
carrier, although this is unlikely.
Shorts on the packet bus occur much more often than do opens. This is because the incorrect insertion of
a circuit pack can cause leads to be shorted together. It is possible for a circuit pack to be the cause of a
packet bus fault but still exhibit trouble-free operation. For example, the insertion of a TDM-only circuit
pack (TN754B Digital Line) could bend the packet bus pins on the backplane. However, since the circuit
pack does not communicate on the packet bus, the pack is not affected by the problem.
Packet bus faults do not necessarily cause service interruptions. However, most packet bus shorts do
cause these interruptions. Depending on what leads are defective, the system may be able to recover and
continue to communicate. This can be detrimental because it makes isolating the fault difficult. The
Maintenance/Test circuit pack provides the capability to detect, and, in some cases, correct packet bus
faults.
Packet bus connectivity
Various circuit packs communicate on the packet bus. For details on ISDN-BRI and ASAI connectivity,
refer to BRI-PORT (ISDN-BRI Port) ABRI-PORT (ASAI ISDN-BRI Port)
Various Adjuncts. For details on Expansion Interface connectivity, refer to
Interface Circuit

Circuit packs that use the packet bus

Four (4) circuit packs can use the packet bus. The following list identifies and discusses each circuit pack.
An explanation of how each circuit pack assists in packet bus maintenance is also included.
NOTE:
The MOs involved with each circuit pack are listed in brackets. Documentation for each
maintenance object is provided in Maintenance Alarms Reference (555-245-102).
TN2314 Packet Control [PKT-INT] provides the SPE interface to the packet bus, just as the
•
TN777 Network Control does to the TDM Bus. All traffic on the packet bus passes through the
packet control.
The packet control can detect failures of certain control leads on the bus. Such failures are
indicated by an inability to transmit data. The packet control can also detect data errors on the
packet bus.
• TN556, TN2198 and TN2208 ISDN-BRI circuit packs [BRI-BD, BRI-PORT, ABRI-PORT,
BRI-SET, BRI-DAT, ASAI-ADJ] provides connections for ISDN-BRI station sets and data
modules and for ASAI adjuncts. The Packet Bus is used to carry signaling information for sets
and data modules. The Packet Bus passes signaling information and ASAI messages between the
SPE and the ASAI adjunct. The ISDN-BRI circuit pack has the same fault detection capabilities
as the TN570 Expansion Interface.
• TN771D (or later) Maintenance/Test circuit pack is the workhorse of packet bus
maintenance. This circuit pack can detect all packet bus failures for the PN in which it resides. In
High and Critical Reliability systems, the circuit pack enables the reconfiguring of the packet bus
248
Pack).
and BRI-SET, BRI-DAT,
EXP-INTF (Expansion
Maintenance Procedures
December 2003