i-modul Modem 336 LL
Functions
6.3
Data Flow Control (Handshake)
The data flow control ensures that the data transfer is interrupted as soon as the modem
buffer exceeds a certain level. Two data flow control options are available: Via the con-
trol lines RTS and CTS, or via the control characters XON/XOFF which are inserted into
the data stream.
6.3.1
Hardware data flow control (RTS/CTS)
The hardware data flow control works in two directions. When the critical buffer level is
exceeded, the modem will set the CTS line to "LOW" and will thus indicate to the applica-
tion to interrupt the dataflow. When the buffer is emptied sufficiently for the i-modul
Modem 336 LL 3.0 to be able to receive data again, the CTS line is set to "HIGH". Re-
versely, the application can also indicate to the i-modul Modem 336 LL 3.0 to interrupt
the data flow. This is done via the RTS line. If it is set to "LOW", the modem will interrupt
the data flow to the application. The application will set it to "HIGH" to request data from
the i-modul Modem 336 LL 3.0.
The data flow control with RTS/CTS behavior is active by default.
Configuration with AT commands
To switch the data flow control on and to set
the type to RTS/CTS, use:
AT&K3
To switch the data flow control off, use:
AT&K0
17
