Specifications

SIM900 AT Command Manual
SIM900_AT Command Manual_V1.03 13 12/24/2010
1.4.2 S Parameter syntax
These AT commands have the format of "ATS<n>=<m>", where "<n>" is the index of the S
register to set, and "<m>"is the value to assign to it. "<m>" is optional; if it is missing, then a
default value is assigned.
1.4.3 Extended Syntax
These commands can operate in several modes, as in the following table:
Table 1: Types of AT commands and responses
Test Command AT+ <x>=? The mobile equipment returns the list of parameters
and value ranges set with the corresponding Write
Command or by internal processes.
Read Command AT+ <x>? This command returns the currently set value of the
parameter or parameters.
Write Command AT+ <x >=< …> This command sets the user-definable parameter
values.
Execution Command AT+ <x > The execution command reads non-variable
parameters affected by internal processes in the GSM
engine.
1.4.4 Combining AT commands on the same Command line
You can enter several AT commands on the same line. In this case, you do not need to type the
"AT" or "at" prefix before every command. Instead, you only need type "AT" or "at" the
beginning of the command line. Please note to use a semicolon as the command delimiter after an
extended command, for example: ATE1&W&F+ICF?; +CFUN?; &W.
The Command line buffer can accept a maximum of 556 characters. If the characters entered
exceeded this number then none of the Command will executed and TA will return "ERROR".
1.4.5 Entering successive AT commands on separate lines
When you need to enter a series of AT commands on separate lines, please Note that you need to
wait the final response (for example OK, CME error, CMS error) of last AT Command you entered
before you enter the next AT Command.
1.5 Supported character sets
The SIM900 AT Command interface defaults to the IRA character set. The SIM900 supports the
following character sets:
• GSM format
• UCS2