At Commands - ADTRAN DSU III AR User Manual

Chapter 4. Configuration Overview

AT Commands

The DSU III AR can be configured and controlled with in-band AT
commands from an asynchronous DTE port just as modems are.
To exit the data mode and enter the command mode, the
asynchronous DTE device must transmit a proper escape sequence
or three pluses (+++) to the DSU III AR. A specified time delay
must occur between the last data character and the first escape
sequence character. This is the guard time delay, and it can be
changed by writing a value to the S12 register. The default value for
the guard time is one second. For a valid escape sequence to occur,
the DTE must transmit the escape code character three times in
succession with delay between each character being less than the
guard time.
Once the command mode is entered, AT commands can be
transmitted to the DSU III AR to configure most of the options or
initiate tests to check both the DSU III AR and the network
connections. All command lines must begin with the AT attention
code in either capital or lower case letters. The command that
follows must match the case of the attention code.
The command line may contain a single command or a series of
commands after the AT attention code. When a series of commands
is used, the individual commands may be separated with spaces for
readability. The maximum length for a command line is 40
characters. Each command line is executed by the DSU III AR upon
receipt of a terminating character. The default terminating
character is a carriage return (ASCII 013), but it can be changed by
writing a different value to register S3.
Before the terminating character is transmitted, the command line
can be edited by using the backspace character (ASCII 008) to erase
errors so the proper commands can be entered.
Valid AT commands for the DSU III AR are listed in Appendix B,
AT Commands on page B-1.
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