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

Serial Programming
Special Commands and Character Sequences

Serial Programming: Introduction and OSI Network Model -- RS-232 Wiring and Connections -- Typical RS232 Hardware Configuration -- 8250 UART -- DOS -- MAX232 Driver/Receiver Family -- TAPI Communications In Windows -- Linux and Unix -- Java -- Hayes-compatible Modems and AT Commands -- Universal Serial Bus (USB) -- Forming Data Packets -- Error Correction Methods -- Two Way Communication -- Packet Recovery Methods -- Serial Data Networks -- Practical Application Development -- IP Over Serial Connections

Hayes-compatable Modems and AT Commands References: -- Special AT Commands and Character Sequences -- AT Commands A - M -- AT Commands N - Z -- AT& Commands

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<command ...><CR>

Description:

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

See the #AT Command Format section for details.

Related Commands and Registers:

#<CR>: End-of-line Character
#A/: Repeat Last Command

+++: Escape Sequence

Syntax:

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

Description:

See: #On-line State to Command State

Result Codes:

Result Codes
Code	Description
OK	Escape into command mode was successful

Related Commands and Registers:

#O: On-Line Command
#S2: Escape Sequence Character -- Register to change the character
#S12: Escape Sequence Guard Time -- register to change the guard time

<CR>: End-of-line Character

Syntax:

AT command line<CR>

Description:

In command mode the end of line character (default ASCII 13, alias ASCII 0dH, alias <CR>, alias <Ctrl-M>, 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:

Result Codes
Code	Description
OK	All commands in the command line were successfully executed.
ERROR	One command in the command line failed.

Related Commands and Registers:

#AT Command Format
#<BS>: Backspace Character
#S3: Carriage Return Character -- Register to change the character.

<BS>: Backspace Character

Syntax:

AT command line<BS>more command line

Description:

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

Result Codes:

Result Codes
Code	Description
<none>	Does not generate a result code.

Related Commands and Registers:

#AT Command Format
#<CR>: End-of-line Character
#S5: Backspace Character -- Register to change the character.

<CAN>: Cancel Character

Syntax:

AT command line<CAN>

Description:

In command mode the cancel character (default ASCII 24, aka ASCII 18H, aka <CAN>, aka <Ctrl-X>) cancels a command line as long as the command line has not been terminated with the #<CR>: End-of-line Character.

Result Codes: