DEFINITY Enterprise Communications Server Release 7
Maintenance for R7r
555-230-126 Issue 4
June 1999
Alarms, Errors, and Troubleshooting
5-80Packet Bus Fault Isolation and Repair
5
Tools for Packet Bus Fault Isolation and Correction
The following tools may be required o n-site to perform pac ket bus fault isolation
and correction.
â– TN771D Maintenance/Test circuit pack for use in stand alone mode, and
the connectors and c ables necessary to install it (see the

Maintenance/Test Circuit Pack

section).
â– A replacement for the TN771D Maintenance/Test circuit p ack in the
system may be needed. See the

A Special Precaution Concerning the

TN771D

section.
â– A backplane pin-replacement kit may be required (see

Packet Bus Fault

Correction

) If the kit is not available, replac ement of a carrier may be
required.
What is the Packet Bus?
The packet bus is a set of 24 lead s in the backplane o f each Port Network.
Twenty of these leads are data leads, three are control lead s, and one lead is a
spare. This distinction is imp ortant only for understanding why some circuit
packs are able to d etect only certain faults; the d istinction does not affec t fault
isolation and repair. Each Port Network has its own p acket bus and there is one
packet bus maintenanc e object (PKT-BUS) in each port network. The packet b us
is not duplicated as is the TDM Bus. There are however several spare leads on
the packet bus and , in Critical Reliability systems (dup licated PNC), these spare
leads are used to recover from some fai lures on the packet bus.
The packet bus carries various types of information:
â– Signaling and data traffic destined for other port-networks and/or Center
Stage Switches. The TN570 Expansion Interface circuit p ack provides
packet bus ac cess for these connec tions.
â– ISDN-BRI signaling information for ISDN-BRI stations, data modules and
ASAI adjunct connections. The TN556 ISDN-BRI circuit p ack provides
packet bus ac cess for these connec tions.
â– X.25 signaling information and data traffic to supp ort system adjunct
applications. The TN577 Packet Gateway circuit pack provides packet
bus access for these connections.
â– ISDN-PRI signaling information carried in the D-c hannels of ISDN-PRI
facilities connected to the switch. The TN464F Universal DS1 circuit pack
provides pack et bus access for these c onnections.
â– System Port tra ffic to support various input/output devices such as dial- up
modems and printers, as well as system adjunct app lications. The TN553
Packet Data circuit pac k provides pac ket bus access for these
connections.