Terminal Adapter At Commands; Entering At Commands - Multitech ISIHI-2S User Manual

Terminal Adapter AT Commands

One of the ways you can communicate with and configure your terminal adapter (TA) is to use AT commands.
AT commands are so-called because, with only a few exceptions, each command string begins with the
characters AT. Using AT commands, you can read and set parameters and perform actions such as dialing.

Entering AT Commands

You can send AT commands to the TA by typing them on the keyboard, by typing them in the terminal window
of a data communications program such as HyperTerminal, or indirectly by configuring your data
communications program.
Enter AT commands in the following format: AT <command string> <cr>. The AT characters cause the TA to
interpret the following string of characters as a command. The command string consists of one or more
commands. The carriage return character, <cr>, sends the command string to the TA. If you are entering a
command string in your communication program's terminal window, insert the carriage return character by
pressing ENTER. On the other hand, if you are configuring a communications program, you typically must insert
the carriage return character by adding ^M to the end of the command string.
The TA has three modes of operation: offline command mode (the default state), online command mode, and
data mode. The TA responds to AT commands only when it is in one of the command modes. After the TA
establishes a connection and goes online in data mode, it interprets any further characters you enter as data
rather than commands and transmits them to the remote device.
When the TA is in data mode, you can switch it to online command mode by sending it an escape sequence. The
TA responds to two types of escape sequences: in-band (escape sequence is part of the data stream) and out-of-
band (escape sequence is outside the data stream). The in-band escape sequence is +++AT<cr>; the out-of-band
escape sequence is <break >AT<cr>. You can change the in-band escape character (+) by changing the value in
register S2. You can send the break signal in the out-of-band escape sequence only from software, not by
pressing SHIFT+BREAK on your keyboard.
When it detects the escape sequence, the TA enters online command mode, in which it responds to commands
while maintaining the connection with the remote device.
The TA 's command buffer can store 80 characters, including spaces and other characters used in telephone
numbers. If you mistype a command string, you can edit it by using the backspace key, but only before you press
ENTER. As you type a command string, it appears on your monitor screen, letting you verify your input as you
type it.
AT commands recognized by the ISIHP terminal adapter are listed by function on the following page. For an
alphabetic list of AT commands, see AT commands in the index. The commands in this chapter are organized by
function. Abbreviated commands are listed on the following page by function along with a short description and
page numbers that refer to a more detailed description, immediately following this list.
Topic
Command Implementation
Command Description
AT Attention code
Return Command execution
+++AT<cr> In-band escape code
A/ Repeat AT command
<break>AT<cr> Out-of-band escape code
Chapter 5 - AT Commands
87