Remote Versus On-Site Maintenance; What Is The Packet Bus - Avaya MCC1 Maintenance Procedures

Packet and serial bus maintenance
Isolating and repairing packet-bus faults
• Packet bus fault isolation flowchart
process. It is used to determine whether a failure of service is caused by the packet bus itself or by
another MO on the packet bus.
• Correcting packet-bus faults
problem with the packet bus itself or one that is caused by a circuit pack connected to the packet
bus.

Remote versus on-site maintenance

Most packet-bus fault isolation and repair procedures require a technician to be on-site. This is because
packet-bus problems are caused by a hardware failure of either the packet bus itself or a circuit pack that
is connected to it. Initial diagnoses can be made using the Packet-Bus Fault Isolation flowchart, but the
Maintenance/Test Stand-Alone Mode and Packet-Bus Fault Correction procedures require an on-site
technician. These procedures are presented with this requirement in mind.
The flowchart refers to the repair procedures for various MOs. When a decision point is reached, a
remotely located technician can refer to the appropriate section and attempt to resolve any fault
conditions. Some procedures require on-site repair action. Keep in mind that failure of an MO appearing
early in the flowchart can cause alarms with MOs that appear later in the flowchart. Multiple dispatches
can be prevented by remotely checking subsequent stages on the flowchart and preparing the on-site
technician for replacement of several components, if necessary.
The Maintenance/Test packet-bus port, described below, provides status information that is accessed with
the status port-network P command and the PKT-BUS test sequence. The Maintenance/Test circuit
pack may or may not be present at a customer site, depending on the configuration of the switch. If a
Maintenance/Test circuit pack is absent, one must be taken to the site for diagnosing packet-bus
problems.
Tools for packet bus fault isolation and
correction
The following tools may be required on-site to perform packet-bus fault isolation and correction.
• TN771D Maintenance/Test circuit pack for use in stand-alone mode, and the connectors and
cables necessary to install it (see
• A replacement for the TN771D Maintenance/Test circuit pack in the system may be needed. See
Entering and exiting stand-alone mode
• A backplane pin-replacement kit may be required (see
If the kit is not available, replacement of a carrier may be required.

What is the packet bus?

The packet bus is a set of 24 leads in the backplane of each PN. Twenty of these leads are data leads, three
are control leads, and one lead is a spare. This distinction is important only for understanding why some
circuit packs can detect only certain faults; the distinction does not affect fault isolation and repair. Each
PN has its own packet bus, and there is one Packet Bus MO (PKT-BUS) for each PN. Unlike the TDM
bus, the packet bus is not duplicated. However, it has several spare leads and, in a critical-reliability
system (duplicated PNC), these spare leads are used to recover from some packet-bus faults.
220
on page 234 is the starting point for the troubleshooting
on page 238 presents the procedures required to correct either a
M/T-BD (Maintenance/Test Circuit
on page 229.
Correcting packet-bus faults
Pack)).
on page 238).
Maintenance Procedures
December 2003