Motorola and V.32bis - Manual (Page 95)

Using the AT Automatic Calling Interface 5-3
Using the
AT
A
C
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What is the Attention (AT) Command Set?
The AT command set is a collection of commands that let you configure a modem
directly from an asynchronous terminal or PC keyboard. The characters AT are a
prefix to the commands you issue to your modem. When you type AT, you are asking
for the modem’s attention. For instance, to disconnect a telephone call, you type AT
for attention and H0 for on-hook (hang up).
You can also use AT commands to configure a remote modem (refer to Chapter 2,
Front Panel Operation, of the 326X Series Modem Reference Guide for details).
What Role Does Communications Software Play?
Some communications software packages “interpret” AT commands with pull-down
menus or graphics, making familiarity with the AT command syntax unnecessary.
Communications software packages that directly support the 326X Series Modem
usually support all of the modem’s AT commands (the industry standard commands
AT, AT&, and the Motorola-enhanced commands AT
* ).
Communications software packages that support a Hayes-compatible selection do
not support the Motorola-enhanced commands (AT
* ). You can enter these
commands yourself to modify option settings if required by your application.
Check the documentation included with your communications software package to
determine whether you need to use AT commands directly.
Using AT Commands
AT commands are accepted by the modem in command mode or escape mode.
• The modem is in command mode when it is disconnected from the
telephone line.
• You can enter escape mode and issue AT commands during a connection
(the escape sequence +++ is described later in this chapter).
Entering AT Command Lines
To enter a single AT command line:
1) Enter the prefix AT: The characters AT (upper-case or lower-case, but not
mixed) must begin the command line.
2) Enter an AT command. For example:
— D instructs the modem to dial a call. H instructs the modem to hang up. A
numeric character (for example, 2) following an AT command instructs
the modem to use a specific command option. If a numeric character is
not indicated, the modem assumes the 0 (zero) option.
3) End with a carriage return <CR>.
The exceptions to the above AT command line conventions are “A/” (repeat last
command) and “+++” (the escape sequence). Responses (result codes) to AT
commands always appear in upper-case.