Technical information

Serial Solutions NewBIOS Reference
DX Register Value.
The DX register is used to specify which serial port is
being used. If DX=0 then COM1 is being used, if DX=3 then
COM4 is being used. The maximum value allowed for DX
depends on which version of NewCOM.SYS has been loaded in
the CONFIG.SYS file. The versions of NewCOM.SYS have
been supplied on the disks:-
NewCOM.SYS supports up to COM16, max DX value = 15.
NewCOM24.SYS supports up to COM24, max DX value = 23.
NewCOM32.SYS supports up to COM32, max DX value = 31.
Error Returns._____________
The services will not return an explicit error code if any of
the supplied parameters is incorrect- for example a port that has
not been set up. For most such errors the service will terminate
harmlessly, though this is not guaranteed, and a bad parameter
may cause unexpected side-effects. The transmit and receive
character services return the status of the transmit/receive
attempt, that is time-outs and receiver errors, if they have been
called with correct parameters. These return codes have been
detailed with the services.
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