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 int erfac e to t he pa cket bus is the TN 1655 Packet Interface circ uit pack.
When SPEs are duplicated, there is one TN1655 in each SPE. The TN771D
Maintenance/Test Circuit Pack (discussed in d etail later) provides pa cket bus
maintenance testing and rec onfiguration capab ilities.
Packet Bus Faults
Two types of packet bus faults occ ur:
Shorts are far more common than opens, since they can be caused by incorrect
insertion of a circuit p ack. It is possible for a c ircuit pack to b e the cause of a
packet bus fault bu t still operate trouble-free itself. For example, the insertion of a
TDM-only circuit pack suc h as a TN754 Digital Line could b end the packet b us
pins on the backp lane, but remain unaffected sinc e it does not communic ate
over the packet bus.
Packet bus faults do not nec essarily cause service interrupti ons, but shorts on it
usually do. Depending on what leads are defective , the system may be able to
recover and continue to c ommunicate. While this allows uninterrupted service, it
makes isolating the fault difficult. The Maintenanc e/Test circuit pack provides the
capability to d etect, and, in some cas es, correct pack et bus faults.
Packet Bus Connectivity
Various circuit packs communic ate on the packet bus (see the next sec tion). For
more details, refer to Chapter 9, ‘‘Maintenance Object Repair Procedu res’’ for the
following circuit p acks:
■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 Pa cket Gatew ay: PGATE- BD, PGATE-PT
■TN553 Packet Data: PDATA-BD, PDATA-PT
Shorts A short occurs when differ ent leads on the packet b us become
electrically connec ted to each other. This can occ ur due to failures of
circuit pac ks, cables between c arriers, TDM/LAN terminators, or
bent pins on the bac kplane. A fault occurring during normal
operation is usually caused by a circuit pa ck. A fault that occurs
while moving circuit p acks or otherwise modifying the switch is
usually due to bent pins on the backplane.
Opens An open occurs when there is a b reak on the packet bus suc h that
the electrical path to the term ination 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 c arrier.