At+Ifc Set Flow Control Separately For Data Directions - Multi-Tech MultiModem EDGE Reference Manual

•
If a <format> is selected without parity (e.g. <format>=3) and you try to activate a format with parity (e.g.,
<format>=2), you need to explicitly set the parameter <parity> (e.g. AT+ICF=2,1). Otherwise you will get
'+CME ERROR: invalid index'. This is because for <format>=3, the parameter <parity> is set to the internal
value 'no parity' which is not supported by <format>=2. (Remember that if an optional parameter is omitted for
which no default is stated in this specification, the value of the parameter remains unchanged).
4.7 AT+IFC Set Flow Control Separately for Data
Directions
Description:
Test Command Syntax:
Response(s):
Read Command Syntax:
Response(s):
Write Command Syntax:
Response(s):
Parameter Descriptions:
<TEflowcontrol>
Specifies the method used by the TA when sending data to the TE.
0
1
2
3
<TAflowcontrol>
Specifies the method used by the TA when receiving data from the TE.
0
1
2
Notes:
•
When using XON/XOFF flow control (AT+IFC=1,x or AT+IFC=3,x) in data mode, +++ should not be used while
the data transmission is paused with XOFF. Before entering the command mode with +++ the paused
transmission should be resumed using the XON character.
•
The two commands AT+IFC and AT\Q influence each other, i.e. settings made with AT\Q apply to AT+IFC
and, vice versa, AT+IFC changes the AT\Q setting.
•
Bear in mind that when you set a flow control method for one direction on the TA (with AT+IFC) the TE must
also be configured accordingly.
•
The values "1" and "2" have only local effect for the connection between TA and TE. Value "3" has an
immediate effect on the over-the-air connection.
• XON/OFF flow control is not recommended for transferring binary files. This is because the data stream might
contain characters equal to the hex values typically used as XON/OFF control characters; i.e., values 11 (hex)
resp. 17 (dec) and 13 (hex) resp. 19 (dec).
Multi-Tech Systems, Inc. AT Commands for EDGE Modems (S000371G)
The command AT+IFC can be used to set or query the data flow control separately for
each data direction. In contrast to this, flow control settings made with AT\Q are valid in
both data directions.
Please note that AT+IFC and the AT\Q commands are designed for configuring only the
TA. The TE must, of course, also be configured. When programming the TE bear in mind
that the flow control method set on the TA must be compliant with the flow control method
set on the TE. See notes below.
AT+IFC=?
+IFC: (list of supported <TEflowcontrol>s), (list of supported <TAflowcontrol>s)
OK
AT+IFC?
+IFC: <TEflowcontrol>, <TAflowcontrol>
OK
AT+IFC=<TEflowcontrol>, <TAflowcontrol>
OK
ERROR
none
XON/XOFF
Local setting on the TA. Terminates flow control in the TA and thus, causes the TA to stop
sending data to the remote TA.
RTS line
Local setting on the TA.
XON/XOFF
Used to evaluate flow control in the TA. If the data flow from the TA requires that the
transmission be stopped, the TE inserts the XON/OFF control characters into the data
stream to be sent, over the air, to the opposite TE. It is the responsibility of the receiving
TE to recognize and filter out from the data stream the XON/OFF control characters. So,
both TEs must have XON/OFF flow control enabled.
Also, the receiving TA must be configured to use software flow control. This means, that if
the sending TA is configured for AT+IFC=3,x the receiving TA must be set to AT+IFC=y,1.
In addition, XON/OFF flow control must be enabled on either TE.
If the TAs and TEs on both sides are properly configured, the transmission of the
XON/OFF control characters will instantly stop the data flow. So, value "3" has an
immediate effect on the over-the-air connection between both TEs.
none. Default.
XON/XOFF
CTS line
Chapter 4 – Serial Interface Control Commands
59