COMSerial/Flow Registry Key
The default setting is NO_CONTROL or 0 meaning that no flow control or
handshaking is used. For the COM RS-232 port the valid settings are:
The COM port does not support hardware handshaking.
The XONXOFF_IN handshake transmits the XOFF character (Ctrl-S 0x13) when
internal buffers reach capacity to hopefully hold off the incoming data.
The XON character (Ctrl-Q 0x11) is later sent to resume communications.
Similarly in XONXOFF_OUT mode the COM port listens for the XOFF character
and stops transmission when received. When a subsequent XON character is
received the communications resume. Both the XON and XOFF characters are
filtered from the stream. The XONXOFF setting applies these rules
HELP Topics: COM_PORT