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From: ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Re: Interrupt sharing
Message-ID: <1991Apr11.141212.11816@bronze.ucs.indiana.edu>
Date: 11 Apr 91 14:12:12 GMT
References: <1991Apr8.170234.24810@lth.se>
Sender: news@bronze.ucs.indiana.edu (USENET News System)
Organization: Indiana University, Bloomington
Lines: 22

>However, is it possible to let two devices (in particular
>a serial port and a parallel port) share an interrupt
>line without the risk of damaging the computer's hardware?

>Although not particularly well informed in this area, I could
>imagine a scenario with one device raising the signal and
>the other one lowering it, causing a "short circuit" between
>+5 volts and 0 volts, or am I way off here?

I always thought the computer's bus uses assertion-
level logic, i.e. if one device causes a line to go 
high, the line will go high no matter what the other
devices on that line are doing. The equivalent of a 
logical multi input OR. Assertion level logic devices
require a terminator resistor between the line and 
ground. 
--
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Iskandar Taib                        | The only thing worse than Peach ala
Internet: NTAIB@AQUA.UCS.INDIANA.EDU |    Frog is Frog ala Peach
Bitnet:   NTAIB@IUBACS               !
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