Technical information

NewBIOS Reference Serial Solutions
Service B0H, Get/Set Hardware Handshake.______________________________________
Compatibility._____________
NewBIOS service only, ignored by PC ROM BIOS.
Parameters.___________
AH = B0H Denotes service B0H
DX = 0...31 Port number, 0=COM1...31=COM32
AL = 00H Denotes read hardware handshake
mode
AL = 01H Denotes set hardware handshake
mode, where
BL = 0..4 Mode, as
0 ==> standard RS232 RTS/DTR
1 ==> RS422 RTS/CTS handshake
2 ==> RS485 half duplex
3 ==> RS485 send only
4 ==> No handshake used,
Txd, Rxd and Gnd only.
Return Values._____________
AX = 53ACH if device driver present, 0H
if NewBIOS is present but
NewCOM is not.
BL = Hardware handshake mode
Meaning._________
Service B0H is used to read or set the hardware handshake
mode used with a particular port. NewBIOS itself does not use
these values, but the NewCOM.SYS device driver does. On a
read 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.
Chapter 5 Page 95