Hardware Data Flow Control With The Pc (Rts); Software Data Flow Control Xon And Xoff - Siemens Insys 56k Operating Manual

Pocket Modem 56k
5.2.5

Hardware Data Flow Control with the PC (RTS)

Modem
The PC sets the RTS line to OFF to request the modem to interrupt
the data transmission.
It will depend on the according PC software, if the RTS/CTS lines are
operated from the PC.
The PC sets the RTS line to ON to request data from the modem.
5.2.6

Software Data Flow Control XON and XOFF

Modem
When the input buffer of the modem exceeds a certain fill state, the
modem will insert an XOFF character into the data stream to the PC.
This character will cause the PC to send no more data.
If the PC supports XON/XOFF data flow control will depend on the
according PC software.
After the modem has processed the input buffer so far, it will insert
a XON character into the data stream. This character will cause the
PC to send data again. Analogously, the PC can control the data
stream from the modem to the PC.
The XON/XOFF method is only available when the transmitted data
do not contain the characters XON or XOFF, which usually means
only in actual ASCII texts (7 bit). When binary data (programs, etc.)
are transmitted, also for BTX operation or in the XMODEM
transmission protocol, for example, occasionally appearing XON or
XOFF characters would disturb the operation.
Dezember 05
RS232 Cable
RTS Line
Send data
XON or XOFF character
PC or control
AT&K
PC or control
AT&K4
Function
AT&R
9