Serial Programming/Modems and AT Commands/Special Commands and Character Sequences

Special Commands and Character Sequences
This module explains the special commands and character sequences as used by a "generic" Hayes-compatible modem. Different modems use slightly different commands. However, this list is supposed to be as "generic" as possible, and should not be extended with modem-specific commands. Instead it is recommended to provide such command lists in an Appendix.

AT: Command Prefix
Syntax:

AT 

Description:

Almost every line with commands start with the  prefix, followed by one or more commands, terminated with a Carriage Return character.

See the section for details.

Related Commands and Registers:
 * 
 * 

+++: Escape Sequence
Syntax:

<1 sec. nothing>+++''<1sec. nothing>''

Description:

See:

Result Codes:

Related Commands and Registers:
 * 
 * -- Register to change the character
 * -- register to change the guard time

: End-of-line Character
Syntax:

AT command line 

Description:

In command mode the end of line character (default ASCII 13, alias ASCII 0dH, alias , alias , alias carriage return) marks the end of a command line. The modem starts to execute the command line after reception of the end-of-line character.

Result Codes:

Related Commands and Registers:
 * 
 * 
 * -- Register to change the character.

: Backspace Character
Syntax:

AT command line  more command line

Description:

In command mode the backspace character (default ASCII 8, alias ASCII 08H, alias , alias , alias backspace) can be used to edit the command line.

Result Codes:

Related Commands and Registers:
 * 
 * 
 * -- Register to change the character.

: Cancel Character
Syntax:

AT command line 

Description:

In command mode the cancel character (default ASCII 24, aka ASCII 18H, aka , aka ) cancels a command line as long as the command line has not been terminated with the.

Result Codes:

Related Commands and Registers:
 * 
 * 

A/: Repeat Last Command
Syntax:

A/

Description:

The command repeats the last command. It differs from other commands in two ways:


 * 1) It is not prefixed with the   command.
 * 2) It should not be followed by the usual  :

The most typical usage is to repeat a previous dialing command that failed because of a  line.

Related Commands and Registers:
 *