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From: jdstovin@cs.man.ac.uk (John Stovin (RNZ ra))
Newsgroups: comp.os.msdos.programmer
Subject: Re: AT PIC, interrupts different?
Message-ID: <2796@m1.cs.man.ac.uk>
Date: 26 Jun 91 10:47:33 GMT
Article-I.D.: m1.2796
References: <4cNX5sO00VpOQ4c0M1@andrew.cmu.edu>
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Reply-To: jdstovin@cs.man.ac.uk (John Stovin (RNZ ra))
Organization: Department of Computer Science, University of Manchester UK
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In article <4cNX5sO00VpOQ4c0M1@andrew.cmu.edu> mh2o+@andrew.cmu.edu (Michael Lorenz Holling) writes:
>I'm having a problem after moving hardware from an XT to an AT.  The hardware
>in question is a MIDI card which is supposed to generate interrupts for a
>variety of reasons.  It worked fine on the XT, however on the AT only one
>interrupt occurs.  I'm guessing it's a problem manipulating the PIC.  On the
>XT I would write 0x20 to port 0x20 to reset the interrupt.  Is there something
>different I need to do on the AT?  I'm using IRQ 2, is there any hardware which
>might be using this line?
>
>Thanks,
>- Mike

Your problem is that the AT has 2 PICs, with the second chained from the
IRQ2 input of the first. You have to reset the interrupts on the chained
PIC as well (I can't remember the port address, but any good reference
should tell you.)




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