Technical information

What To Do First Serial Solutions
transmits data when the master commands it to do so.
The RS485 full duplex handshake, from a software point
of view, is identical to the 3 wire no handshaking option and so
is passed to the NEWCOM.SYS driver by the /Hr,4 parameter.
Where r is the COM port number, r may be a single port or a
range of ports. For example:-
/H1,4 sets up no handshaking (485 full duplex) for COM1.
/H12,4 sets up no handshaking (485 full duplex) for COM12.
/H7-16,4 sets no h/shake (485 full duplex) for COM7 to
COM16.
Chapter 1 Page 17