multiple communication ports

[Ivar Hosteng]

I have a problem using my serial ports with Xenix 386 2.3.2. I have a standard
dumb com4 card with no polling register. The card can use IRQ lines 2,3,4,5.
I have managed to use 3 of the ports by assigning them to IRQ 3,4 and 5 and by
editing my master and sioconf.c file. But I cannot enable the fourth port.
Is there a way to let two of the ports use the same IRQ line and making an 
entry like this in the sioconf.c file:

{0,IBM_BOARD,   2,4,0,  (sd)0x3e0,0,                8,MCRBIT3}

When I do this Xenix finds the ports in the boot sequence but when I try to
write to the port the task hangs until I press DEL. Nothing gets written to
the port. 

Please answer by email. Thanks in advance for the answers I get
-- 
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Ivar E. Hosteng,	Advanced Computer Consultans, Oslo, Norway
Internet:		ivar at acc.uu.no
UUCP:			...!{uunet,mcvax,ifi}!is.uu.no!ivar