Alarms, Errors, and Troubleshooting
555-233-143
4-84 Issue 1 May 2002
Packet-Bus Faults
Two types of packet-bus faults can occur:
Shorts are far more common than opens since they can be caused by incorrect
insertion of a circuit pack. It is possible for a circuit pack to cause a packet-bus
fault, but still operate trouble-free itself. For example, the insertion of a TDM-only
circuit pack such as a TN754 digital line could bend the packet-bus pins on the
backplane but remain unaffected, since it does not communicate over the packet
bus.
Packet-bus faults do not necessarily cause service interruptions, but shorts on it
usually do. Depending on which leads are defective, the system may recover and
continue to communicate. While this recovery can provide uninterrupted service,
it also makes isolating a fault more difficult. The Maintenance/Test circuit pack
enables the detection and, in some cases, correction of packet-bus faults.
Packet-Bus Connectivity
Various maintenance objects communicate on the packet bus (see the next
section). For more details, see Maintenance-Object Repair Procedures for the
following MOs:
■ TN2312 ‘‘IP-SVR (IP Server Interface)’’ on page 8-959
■ ‘‘PKT-INT (Packet Interface)’’ on page 8-1238
■ TN570 ‘‘EXP-INTF (Expansion Interface Circuit Pack)’’ on page 8-762
■ TN556 ISDN-BRI:
— ‘‘BRI-BD/LGATE-BD (ISDN-BRI Line Circuit Pack)’’ on page 8-321
— ‘‘BRI-PORT (ISDN-BRI Port), ABRI-PORT (ASAI ISDN-BRI Port)’’
on page 8-330
— ‘‘BRI-SET, ASAI-ADJ, BRI-DAT’’ on page 8-354
■ TN464F Universal DS1:
— ‘‘UDS1-BD (UDS1 Interface Circuit Pack)’’ on page 8-1707
— ‘‘ISDN-LNK (ISDN-PRI Signaling Link Port)’’ on page 8-970
Shorts A short occurs when different leads on the packet bus become electrically
connected to each other. This can occur due to failures of circuit packs, cables
between carriers, TDM/LAN terminators, or bent pins on the backplane. A fault
occurring during normal operation is usually caused by a circuit pack. A fault
that occurs while moving circuit packs or otherwise modifying the switch is
usually due to bent pins on the backplane.
Opens An open occurs when there is a break on the packet bus such that the
electrical path to the termination resistors is interrupted. Usually, this break is
caused by a failed TDM/LAN cable or terminator. A less likely possibility is a
failure in the backplane of a carrier.
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