Help....

I need to implement COM3 and COM4 on a board that I'm designing and I'm
finding it dificult to track down a definition (hardware that is) of COM3
and COM4.

I have the IO adresses and the fact that COM3 shares IRQ4 with COM1 and COM4
shares IRQ3 with COM2, except exactly how this IRQ sharing is done is not
clear especially if the existing COM1/2 does not allow IRQ sharing. Does the
standard??? allow for a different IRQ to be used and if so how.

Please answer by email to :-

      neil@stone.oz.au

thanks in advance