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SIM900 AT Command Manual
SIM900_AT Command Manual_V1.03 14 12/24/2010
• HEX
• IRA
• PCCP
• PCDN
• 8859-1
The character set can be set and interrogated using the "AT+CSCS" Command (GSM 07.07).
The character set is defined in GSM specification 07.05.
The character set affects transmission and reception of SMS and SMS Cell Broadcast messages,
the entry and display of phone book entries text field and SIM Application Toolkit alpha strings.
1.6 Flow control
Flow control is very important for correct communication between the GSM engine and DTE. For
in the case such as a data or fax call, the sending device is transferring data faster than the
receiving side is ready to accept. When the receiving buffer reaches its capacity, the receiving
device should be capable to cause the sending device to pause until it catches up.
There are basically two approaches to achieve data flow control: software flow control and
hardware flow control. SIM900 support both two kinds of flow control.
In Multiplex mode, it is recommended to use the hardware flow control.
1.6.1 Software flow control (XON/XOFF flow control)
Software flow control sends different characters to stop (XOFF, decimal 19) and resume (XON,
decimal 17) data flow. It is quite useful in some applications that only use three wires on the serial
interface.
The default flow control approach of SIM900 is hardware flow control (RTS/CTS flow control), to
enable software flow control in the DTE interface and within GSM engine, type the following AT
Command:
AT+IFC=1, 1
This setting is stored volatile, for use after restart, AT+IFC=1, 1 should be stored to the user
profile with AT&W.
NOTE:
The AT commands listed in the table of AT&W chapter should be stored to user profile with
AT&W for use after restart. Most other AT commands in V.25, 07.05, 07.07, GPRS will store
parameters automatically and can be used after module restart.
Ensure that any communications software package (e.g. Hyper terminal) uses software flow
control.
NOTE:
Software Flow control should not be used for data calls where binary data will be transmitted or