Flow Control; Software Flow Control (Xon/Xoff Flow Control) - Quectel M35 Command Manual

GSM/GPRS Module
M35 AT Commands Manual
The character set can be configured 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.

1.4. Flow Control

Flow control is very important for correct communication between the GSM engine and DTE. For example,
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. M35 supports both two kinds of flow control.
In Multiplex mode, it is recommended to use the hardware flow control.
The default f low control approach of M35 is closed.

1.4.1. 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 M35 is closed, to enable software flow control in the DTE interface
and within GSM engine, type the following AT command:
AT+IFC=1, 1<CR>
This setting is stored volatile, for use after restart, AT+IFC=1, 1<CR> should be stored to the user profile
with AT&W<CR>.
Ensure that any communication software package (e.g. ProComm Plus, Hyper Terminal or WinFax Pro)
uses software flow control.
NOTE
Software Flow Control should not be used for data calls where binary data will be transmitted or received
(e.g. TCP/IP), because the DTE interface may interpret binary data as flow control characters.
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