User`s guide

7-4
Diagnostics and Troubleshooting
7.2.3 Software Checksum Comparison
When the ATX reboots, its operational software is verified by a
checksum comparison before it is loaded. If the software fails the
checksum test due to an aborted new software distribution
procedure, the ATX will automatically use its backup version of
software. (A backup version of software is always stored in
nonvolatile memory.)
The operational parameters of the ATX software are also protected
by a checksum comparison. When the ATX reboots, if the
operational parameters of the ATX fail a checksum test due to a
power failure in the midst of a previous update, the ATX will
automatically use its backup version of the parameters. (A backup
version of the operational parameters is always stored in
nonvolatile memory before any update is attempted.)
7.2.4 Power-up Diagnostics Results
After completion of the power-up diagnostic sequence, all STATUS
LEDs on the ATX front panel should be on, indicating that the
modules have passed the power-up tests.
7.2.5 Responses to Failures at Power-up
How the ATX responds to failures detected during power-up
depends on the seriousness of the failure. For example, a failure
detected on an interface module will not prevent the ATX from
booting; it will only cause the particular interface module to go out
of service. If an interface module fails power-up diagnostics, it is
automatically disabled. The rest of the ATX system will continue to
operate. Similarly, the ATX will operate if a non-critical component
such as the out-of-band management port on the PPE fails
diagnostics.
However, in the event of a critical failure such as a failure of the
main element processor, local RAM or SRAM, the ATX will halt
execution and will not boot to operational mode.