Polycom MGC Administrator, Administrator'S Manual

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MGC Administrator’s Guide
5-29
Telnet
The Telnet function is used to connect to another computer or MCU for file
maintenance. The access to the MCU via Telnet is password protected, as
with normal logging into the MCU. This function is intended for Polycom's
internal use only.
IP Terminal
The IP Terminal is a feature used for debugging and recording traces of
specific tasks that have been suspended due to an exception. An exception is
an interruption to the normal flow of a program. The traces can then be
analyzed to determine the source of the problem. The following are common
exceptions:
• Division by zero
•
Stack overflow
•
Disk full errors
• I/O (input/output) problems with a file that is not open
The path of each task is recorded in its stack (a set of data storage locations
that are accessed in a fixed sequence), and the IP Terminal feature traces all
the addresses within that task’s stack until the system finds the stage at which
the exception occurred.
The system reads the value of the task’s stack’s first DWORD’s (32 Bit) ESP
(extended stack pointer) register values at the exception handling stage. This
is done in a similar way to the mechanism that already exists in the system, by
reading the EBP (extended base pointer) register values. The stack’s contents
are copied to a file. A new file is created every time the MCU is reset. It is
possible to copy the contents to an existing file, in which case, the old data
will be lost, as the latest traces will overwrite the file.
The IP Terminal only records traces of the first exception. The system is based
on the assumption that the first exception is also the cause of other exceptions
that may follow.