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<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: + Result Codes Code Description <none> No result code is returned. Related Commands and Registers: #AT Command Format [[#<BS>: Backspace Character]] A/: Repeat Last Command Syntax: A/ Description: The command repeats the last command. It differs from other commands in two ways: It is not prefixed with the AT command. It should not be followed by the usual <CR>: The most typical usage is to repeat a previous dialing command that failed because of a BUSY line. Related Commands and Registers: #D: Dial Command