Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!ukma!simon
From: simon@ms.uky.edu (Simon Gales)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Com3 and Com4
Message-ID: <10569@s.ms.uky.edu>
Date: 16 Nov 88 02:37:27 GMT
References: <2677@silver.bacs.indiana.edu>
Reply-To: simon@ms.uky.edu (Simon Gales)
Organization: U of Kentucky, Mathematical Sciences
Lines: 34

In article <2677@silver.bacs.indiana.edu> millerp@silver.bacs.indiana.edu (Lost My Mind) writes:
>
>Hi, I'm working on a terminal emulation program at work and I've
>run into a slight problem. One of the tech's here has an IBM Clone
>and they want to put their 'Internal Half-Card' Modem in as either
>Com3 or Com4 depending on ???? Anyway, I need to know what the interrupt
>vector address for these comports are, I can't find it in my manual 
>mound. I know where the control registers for these comports are, so
>if someone could e-mail or post the interrupt vector addresss for these
>comports I would really appriciate it.

Port addresses for the 3rd/4th serial port depends entirely upon the 
card you are using - look it up in its manual.  Normally you must set 
the int# that each port uses to either 3 or 4, using dip switches on 
the card.

COM3 and COM4 normally use the same interrupt as COM1 and COM2.  
COM3 uses int4, COM4 uses int3.  This sort of messes with using 
COM1&3 or 2&4 at the same life, but thats life with DOS.  

Placing the port addressess of com3 & 4 at 0040:0004 and 0040:0006 (this
is the bios port table) allows many popular programs to use them.  

>Pam Miller

<-------------------------------------------------------------------------->
<---   Simon Gales@University of Ky                 263-2285/257-3597   --->
<---            [ simon@ms.uky.edu ]  |  [ simon@UKMA.BITNET ]          --->
<-------------------------------------------------------------------------->
-- 
<-------------------------------------------------------------------------->
<---   Simon Gales@University of Ky                 263-2285/257-3597   --->
<---            [ simon@ms.uky.edu ]  |  [ simon@UKMA.BITNET ]          --->
<-------------------------------------------------------------------------->