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To: gtc@aloft.att.com (gary.corcoran)
cc: Brett_Glass@ccgate.infoworld.com, alex@fa.tdktca.com, bde@zeta.org.au,
        E00114@vnet.atea.be, freebsd-hardware@freebsd.org
Subject: Re: Multiple COM ports with same IRQ 
In-reply-to: Your message of Fri, 19 Jul 96 17:35:10 -0400.
             <9607192135.AA15984@stargazer> 
Date: Fri, 19 Jul 1996 21:30:09 -0700
From: "Michael L. VanLoon -- HeadCandy.com" <michaelv@HeadCandy.com>
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>One question though: The "open-collector" scheme described above (which is
>what is commonly used for interrupt sharing) works quite well for 
>ACTIVE LOW interrupt signalling.  But the IRQ lines on EISA (and ISA)
>are ACTIVE HIGH signals.  Do EISA PICs also allow the active state of
>the bus IRQs to be changed from high to low? (I don't think so).

>From the vague references I found quickly scanning through my BusLogic
Technical Reference Manual, it indeed appears the state of the signal
is inverted depending on which mode it is running in.

-----------------------------------------------------------------------------
  Michael L. VanLoon                                 michaelv@HeadCandy.com
        --<  Free your mind and your machine -- NetBSD free un*x  >--
    NetBSD working ports: 386+PC, Mac 68k, Amiga, Atari 68k, HP300, Sun3,
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