Chapter 2: Introduction to AT Commands
April 15, 2008 G24-L AT Commands Reference Manual 2-3
AT Commands Structure
Command Structure
An AT command line may contain one or more commands. Delimiters are used to separate the
commands from each other, according to the following structure:
Each AT command has the "AT" prefix string.
Each AT command has the suffix <CR>.
The delimiter is either a semicolon ";" or none, meaning space (basic commands).
Each AT command has the following structure:
The following figure outlines the basic structure of an AT command line:
Figure 2-2: Basic Structure of a Command Line
The following rules must be observed when issuing a command line to the modem:
• Every command line must begin with the letters AT.
• Several commands can be concatenated as one line, as long as the total line does not exceed
140 characters with semicolon characters.
• Characters:
Spaces are ignored. You can leave spaces between each command and between characters of a
command. You can also include punctuation in telephone numbers, and type commands in either
UPPERCASE or lowercase. For example, the following commands are identical:
ATDT8005551234 < Enter > or
atdt (800) 555-1234 < Enter >
Backspace <S5> character is allowed.
• To cancel a dialing command in progress, send any ASCII character to the modem.
• To execute the command line, send the <CR> ASCII character.
Prefix Command1 Delimiter Command2 Delimiter … CommandN Suffix
Token Mode Arguments
ATCMD1 CMD2=12; +CMD1; +CMD2=,,15; +CMD2?; +CMD2=?<CR>
Command
line prefix
Basic command
(no + prefix)
Subparameters
may be omitted
Extended command
(prefixed with +)
Test command for checking
possible subparameter values
Extended commands are
delimited with semicolon
Command line
termination character
Subparameter
Read command for checking
current subparameter values
