Functions
INSYS WLAN serial 2.1
11.2
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. There are two possibilities for data flow control: via the
control lines RTS and CTS, or via the control characters XON/XOFF which are inserted into
the data stream.
11.2.1
Hardware Data Flow Control (RTS/CTS)
The hardware data flow control works in two directions. When the critical buffer level is
exceeded, the INSYS WLAN serial 2.1 will set the CTS line to "low" and will thus indicate
to the application to interrupt the data flow. When the buffer is emptied sufficiently for
the INSYS WLAN serial 2.1 to be able to receive data again, the CTS line is set to "high".
Reversely, the application can also indicate to the INSYS WLAN serial 2.1 to interrupt the
data flow. This is done via the RTS line. If it is set to "low", the INSYS WLAN serial 2.1 will
interrupt the data flow to the application. The application will set it to "high" to request
data from the INSYS WLAN serial 2.1.
The data flow control with RTS/CTS behaviour is active by default.
Configuration with HSComm
On the "Basic settings" tab in the "Handshake" panel (Figure 6, page 44, posi-
tion 2), the
hardware data flow control
can be selected or disabled at all.
Configuration with AT commands
In order to
enable data flow control
and set
the type to RTS/CTS, use the command:
AT&K3
In order to
disable data flow control
, use the
command:
AT&K0
.
11.2.2
Software Data Flow Control (XON/XOFF)
When the input buffer of the INSYS WLAN serial 2.1 exceeds a certain fill state, the INSYS
WLAN serial 2.1 will insert an XOFF character into the data stream to the application.
This character will cause the application to send no more data. It depends on the accord-
ing application software if XON/XOFF data flow control is supported.
After the input buffer of the INSYS WLAN serial 2.1 is emptied sufficiently that data can
be received again, the INSYS WLAN serial 2.1 will send an XON character to the applica-
tion. This character will cause the application to send data to the INSYS WLAN serial 2.1
again. Analogously, the application can insert XON/XOFF characters into the data stream
to switch the data flow on and off. The XON/XOFF data flow control is only available
when the transmitted data do not contain the characters XON or XOFF, which usually
appear only in actual ASCII texts (7 bit). When binary data (programs, etc.) are transmit-
ted, or in the XMODEM transmission protocol, for example, occasionally appearing XON
or XOFF characters would disturb the operation.
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Summary of Contents for WLAN 2.1
Page 1: ...Manual INSYS WLAN serial 2 1 Sep 10...
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Page 93: ...INSYS WLAN serial 2 1 Declaration of Conformity 19 Declaration of Conformity 93...
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