DEFINITY Enterprise Communications Server Release 7
Maintenance for R7r
555-230-126
Issue 4
June 1999
Alarms, Errors, and Troubleshooting
5-81Packet Bus Fault Isolation and Repair
5
The SPE interface to the packet bus is the TN1655 Packet Interface circuit pack.
When SPEs are duplicated, there is one TN1655 in each SPE. The TN771D
Maintenance/Test Circuit Pack (discussed in detail later) provides packet bus
maintenance testing and reconfiguration capabilities.
Packet Bus Faults
Two types of packet bus faults 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 be the cause of 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 what leads are defective, the system may be able to
recover and continue to communicate. While this allows uninterrupted service, 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 (see the next section). For
more details, refer to
Chapter 9, ‘‘Maintenance Object Repair Procedures’’
for the
following circuit packs:
■ TN1655 Packet Interface: PKT-INTF
■ TN570 Expansion Interface: EXP-INTF
■ TN556 ISDN-BRI: BRI-BD, BRI-PORT, ABRI-PORT, BRI-SET, BRI-DAT,
ASAI-ADJ
■ TN577 Packet Gateway: PGATE-BD, PGATE-PT
■ TN553 Packet Data: PDATA-BD, PDATA-PT
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.
