Avaya Definity SI, Maintenance Manual, Page: 757 / 2968

Circuit Packs That Use the Packet Bus
Issue 4 May 2002 9-5 555-233-123
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 (see next section).
For details on ISDN-BRI and ASAI connectivity, refer to “BRI-PORT” and
“BRI-SET/ASAI-ADJ” in
Chapter 10, ‘‘Maintenance Object Repair Procedures’’ .
For details on Expansion Interface connectivity, refer to “EXP-INTF”.
Circuit Packs That Use the Packet Bus
Four 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
Chapter 10,
‘‘Maintenance Object Repair Procedures’’ .
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TN778 Packet Control [PKT-CTRL] 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.
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TN570 Expansion Interface [EXP-INTF] is used to connect the PNs in the
system. For systems that use the packet bus, all Port Network connections
must be made with TN570 circuit packs. All packet traffic between PNs
passes through a pair of TN570s (one in each port network).
The Expansion Interface can detect a subset of control lead failures
(though not as many as the packet control), and it can detect many data
lead failures via parity errors on received data.