Technical information

Serial Solutions Using NewBIOS
services is referred instead to our routines.
To sum up, if the user loads NewCOM or runs NewBIOS
the ROM serial communications routines are replaced by the
routines of NewBIOS. These allow up to 16 serial ports to be
used and add several extra functions.
Overview Of Asynchronous Services.________________________________
NewBIOS mimics all the services provided by the ROM
BIOS of the PC and the extra facilities of the PS/2 ROM BIOS.
These functions are extended to cover 16 ports and service 4H,
the PS/2 extended initialise, supports extra baud rates. The
services are as follows. Note that the service numbers are in
hexadecimal, and all services except AEH are directed towards
specific ports.
Service 0H, Initialise communications port.
This sets the port parameters. These are the baud rate,
parity, number of stop bits and word length.
Service 1H, Send character.
Send a single (usually ascii) character to the port.
Service 2H, Receive character.
Receive a single character from the port.
Service 3H, Read status.
The state of the RS232 handshake input lines and the
status of the serial chip (including things like reception
errors, chip ready to send data) are returned. The other
standard services return some or all of this information
anyway.
Service 4H, Extended initialise.
Provided on the PS/2 ROM BIOS (and on NewBIOS for
all PCs), this performs a similar function to service 0H, but
allows a wider range of parameters to reflect the full
capabilities of the serial chip and is somewhat easier to
use. The NewBIOS version extends the ranges of baud
rates available still further.
Service 5H, Extended communications port control.
This allows us to read, via subservice 0, the state of the
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