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Chapter 6. Configuration
36
ISU 2x64 Dual Port ISDN Service Unit User Manual 61200051L1-1D
20 sec or EON: The ISU 2x64 assumes the dial string is fully entered if more than
20 seconds elapse since the last digit was keyed, or the unit
receives the EON command.
Wait for EON: The ISU 2x64 assumes the dial string is fully entered only if the
unit receives the EON command.
AT Commands
Configuring the ISU 2x64 for AT commands enables inband dial-
ing over a DTE interface using asynchronous AT commands. AT
commands can be used to set up the ISU 2x64 as well as establish
and end a call. Calls can be disconnected from the front panel (as
described previously) or from the far-end unit. Do not set the unit
up for AT command in synchronous applications.
When AT commands are selected, the DTE port becomes dual
purpose. First, while a call is not established, the port accepts AT
commands. During this time, the CD signal is inactive. Second,
when a call is established, the port is used for data. This data
mode is indicated by the CD signal active. See the appendix AT
Commands for a listing of the supported AT commands and their
functions. In addition to the front panel, the ISU 2x64 can be con-
figured and controlled with inband AT commands from an asyn-
chronous DTE port just as modems are.
To exit data mode and enter command mode, the asynchronous
DTE device must transmit a proper escape sequence to the ISU
2x64. 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. The
default escape sequence is +++.
Once command mode is entered, AT commands can be transmit-
ted to the ISU 2x64 to configure most of the options, dial remote
ISUs, or initiate tests to check both the ISU 2x64 and the network
connections. All command lines must begin with the AT charac-
ter set in either capital or lower case letters. A command line can