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Chapter 6. Configuration
61202.029L2-1 ISU 128 User Manual 31
To exit the data mode and enter the command mode, the asynchronous DTE
device must transmit a proper escape sequence to the ISU 128. A specified
time delay must occur between the last data character and the first escape se-
quence character. This is the guard time delay, and it can be changed by writ-
ing 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 es-
cape code character three times in succession with delay between each charac-
ter being less than the guard time. The default escape sequence is +++.
Once the command mode is entered, AT commands can be transmitted to the
ISU 128 to configure most of the options, dial remote DSUs, or initiate tests to
check both the ISU 128 and the network connections. All command lines must
begin with the AT character set in either capital or lower case letters and end
with a terminating character. A command line can be terminated at any time
by transmitting the Ctl-X (ASCII 018) after the AT attention code. The ISU 128
ignores this command line and issues an OK response.
The command line may contain a single command or a series of commands af-
ter the AT attention code. When a series of commands are 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 ISU 128 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 back-
space character (ASCII 008) to erase errors so the proper commands can be en-
tered. Examples of using AT commands are provided in this section.
Using AT Commands
Type AT followed by the letter of the command and numeric value of the set-
ting desired and then press Enter. The following command returns the soft-
ware version of the unit:
ATI1
Using S-Registers
The configuration of the ISU 128 can be changed and/or reviewed with S-reg-
isters. See the appendix S-Register List for a description of each S-register and
its corresponding range of values.