Table of Contents
Advertisement
MT5634HD8/16 User Guide
Working with AT Commands
The MT5634HD8/16's modems are controlled by instructions called AT commands , so called because the
attention characters AT precede each command or sequence of commands (known as a command string ).
You can send commands to the modem from your keyboard while in terminal mode, or you can use
communications software to issue these commands automatically.
The modem is in command mode when it is not dialing or online. When it is in command mode, you have
access to a complete communications system that allows you to use several features, including the basic
AT command set described in this chapter. Using the basic AT command set, you can enter phone
numbers for automatic dialing, configure modem options, and monitor telephone activity. In addition,
you can command your modem to perform advanced features such as error correction, data compression,
speed conversion, and more.
This chapter describes the modem's operational modes, and shows you how to use each of the modem's
AT commands. These commands and responses are compatible with all systems and with all data
communications software using the AT command set.
Modes of Operation
The MT5634HD8/16 operates in two basic functional modes: command mode and online mode . (There is
also an in-between state, wait-for-carrier , in which the modem is out of command mode but not yet
online.) When you power up the modem, it is in command mode, and is ready to accept and respond to
commands from your keyboard or software.
The modem enters online mode after it dials, connects with another modem, and detects a valid carrier
signal. If it does not detect a carrier signal within the time frame controlled by register S7, the modem
abandons the call and re-enters command mode.
You can make the modem enter online mode without dialing by typing either the D command or the A
command.
The modem exits online mode if the carrier signal is lost or intentionally dropped. When this happens, the
modem hangs up and re-enters command mode.
By sending certain "escape" characters to the modem while online, you can make it enter command mode
without losing the carrier signal.
Command Structure
You can control a wide variety of modem operations and options when the modem is in command mode.
AT commands tell the modem to dial a number, to answer a call, to operate at a certain speed, to use a
certain compression technique, and many other functions. AT commands consist of one or two letters,
which may be preceded by an ampersand ( & ), a percent character ( % ), or a slash character ( \ ). The Q
command, for example, determines whether the modem returns result codes, while the &Q command
selects the asynchronous communications mode.
12
CommPlete Communications Server
Advertisement
Table of Contents
