Path: utzoo!utgpu!watmath!clyde!att!whuts!homxb!hound!rkl1
From: rkl1@hound.UUCP (K.LAUX)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Com3 and Com4
Summary: there are no interrupt vectors for COM3 and COM4
Message-ID: <2748@hound.UUCP>
Date: 15 Nov 88 17:30:28 GMT
References: <2677@silver.bacs.indiana.edu>
Organization: AT&T Bell Laboratories, Holmdel
Lines: 10


	Unfortunately, there are no interrupt vectors for COM3 and COM4 on a
PC/XT.  What you would need to do is to enable COM3/4 ports to interrupt on
IRQ2/3 and the interrupt routines would have to POLL the ports attached to
the IRQ to see which one actually issued the interrupt.

	If the COM1/2 ports are NOT interrupt driven but polled, then simply
assign COM3/4 to IRQ2/3; but if they are, you have to do as described above.

--rkl