Black Box MD1276A, User Manual

Page: 14 / 289

Page 14
The AT Commands
The AT commands are a group of special commands recognised by your modem. These
commands derive their name from the letters AT, which are used to prefix commands. Before
continuing:
•
Run your communications software and enter local mode (or terminal mode) at 38,400 bps
Refer to your communication software manual for details.
The Attention Code
An AT (sometimes known as the ATtention code) usually precedes all commands being sent to
the modem. It is used to gain the modem
’ s attention, informing it that you are about to send a
command. For example:
•
Type the command: ATI9 <E>
Your modem
’ s firmware identity message will appear on your computer screen. If you type I9
only, your modem will not respond. If you type AT19, your modem will report an ERROR.
You may enter the attention code in all upper case, or all lower case letters, such as: AT or at
Multiple Commands
You may place multiple modem commands after an AT provided the total number of characters
does not exceed 80. For example, a valid command to display the modem
’ s firmware identity
twice is:
•
Type in the command: ATI9I9 <E>
An AT is not required in front of the second I9 command. You only need one attention code for
each command line. To make this command more readable, you can add spaces between the two
commands:
•
Type in the command: AT I9 I9 <E>
The modem will execute the command as if the spaces are not there.
The Escape Sequence
When you issue commands to the modem all dialogue is occurring between your computer and
the modem. This situation is known as local command state.
When you connect to a remote system, dialogue will be occurring between your computer and
the remote system. This is known as on-line state. Because the modem assumes, after it enters
on-line state, all the data you send it is to be sent on to the remote modem, it ignores any AT
commands you give it while in on-line state.
To force the modem to return to local command state, enter an escapesequence. An escape
sequence consists of a one second delay, three + characters typed rapidly and another one
second delay. For example: