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CHAPTER 5: Configuration Overview
NOTE
Because a VT100 terminal has better display capabilities, the VT100
menu structure differs from the front-panel interface. Appendix C
includes the VT100 screens as well as a complete menu tree for
accessing configuration selections. Descriptions of individual menu
options are provided throughout this manual based on the front-panel
menu structure. See Figure 5-1 for the front-panel configuration menu
tree.
C
OMMANDS
The CSU/DSU MS DBU 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 of three pluses (+++) to the
CSU/DSU MS DBU. 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
CSU/DSU MS DBU to configure most of the options or initiate tests to check
both the CSU/DSU MS DBU and the network connections. All command lines
must begin with “AT” in either capital or lower-case letters.
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 by spaces for readability. The maximum length for a
command line is 40 characters. Each command line is executed by the CSU/DSU
MS DBU 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.
NOTE
Not all parameters can be selected using these commands. Valid
commands are listed in Appendix B.