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61200.153L1-13 Express XR/XRT Quick Start Guide 51
Appendix A. AT Commands and S-Registers
Appendix A
AT Commands and S-Registers
AT Commands
While a call is not established, the DTE port accepts AT com-
mands. During this time, the CD signal is inactive. When a call
is established, the port is used for data. This data mode is
indicated by the CD signal active. The Express XR/XRT can be
configured and controlled with AT commands from a serial port
similarly to analog modems.
To exit data mode and enter command mode, the serial port
must transmit a proper escape sequence to the Express XR/XRT.
A specified time delay must occur between the last data charac-
ter 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. The
default escape sequence is +++.
Once command mode is entered, AT commands can be transmit-
ted to the Express XR/XRT to configure most of the options, dial
remote Express XR/XRTs, or initiate tests to check both the
Express XR/XRT and the network connections. All command
lines must begin with the AT character set in either capital or
lower case letters. To return an active call to the on-line state
type ATO.
The command line may contain a single command or a series of
commands after the AT attention code. AT commands _L1 and
_L0 are exceptions and must be on a separate line followed by
Enter. When a series of commands are used, the individual