Technical information

Serial Solutions NewBIOS Reference
Service ADH, Set Port Address.____________________________
Compatibility._____________
NewBIOS service only, ignored by PC ROM BIOS.
Parameters.___________
AH = ADH Denotes service ADH
DX = 0...31 Port Number 0=COM1...31=COM32
BX = Port address
Return Values._____________
AX = 52ADH Flag for presence of NewBIOS
BX = Old port address
Meaning._________
Service ADH informs NewBIOS of the I/O addresses of
the ports installed in the machine. The value in BX is swapped
with that in NewBIOS’ list of addresses. For COM1 to COM4
the list maintained by the ROM BIOS is also updated.
The AX register is set to the value 52ADH as a flag that
NewBIOS has been installed. The ROM BIOS services will not
report an error if the user attempts to use their non-existent
service ADH, so applications which require NewBIOS should
check this at least once.
Other Points.____________
A port with an address of 0 is regarded as ’unset’ or ’not
present’.
It is best to set the port addresses using the /A command
on the NewCOM.SYS line in the CONFIG.SYS file.
This service, along with service AFH, should perhaps be
best used via a program executed by the autoexec.bat file when
the machine is booted. This leaves the serial ports correctly set
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