Technical information

Serial Solutions NewBIOS Reference
Service B1H is used to read or set the software handshake
mode used with a particular port, and to select the characters
that are to be used as XON and XOFF. NewBIOS itself does
not use these values, but the NewCOM.SYS device driver does.
On reading the handshake mode the value of the mode for the
port is returned in BL, and on a write the value in BL is used to
set the mode used with the port. On reading the XON and
XOFF characters the values of the characters are returned in BL
and BH respectively, and on a write BL and BH are used to set
the characters.
The default is to have software handshaking disabled, and
to use ascii character 17 (DC1) as XON and ascii 19 (DC3) as
XOFF.
Chapter "What To Do First", section "Handshake
Selection" gives more details of the software handshake.
Other Points.____________
NewBIOS will allow the setting of handshake modes for
ports whose address has not yet been set, but their address
remains zero and they cannot be used.
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