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Subject: Re: ISA IRQ signal active how long?
Date: Fri, 04 Oct 2002 20:26:36 -0400
Organization: Arius, Inc
References: <email@example.com> <3d9d9197.236773705@News.CIS.DFN.DE> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: 5 Oct 2002 00:26:37 GMT
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Meindert Sprang wrote:
> "Norm Dresner" wrote in message
> > Meindert Sprang wrote in message
> > news:firstname.lastname@example.org...
> > > Oops, I got that wrong. But if the interrupts are edge sensitive, why on
> > > earth should the signal remain active until serviced????
> > >
> > Every standard 8259 PIC is programmable as to level or edge trigger
> I know that. But the fact remains that the ISA bus spec says it should be
> edge sensitive while the signal should remain active until serviced. That
> just makes no sense.
IIRC, you can read the state of the IRQ pin from the PIC. So if the IRQ
is held you can distinguish spurious interrupts from real ones. Don't
know if this is how it is used or not. I do know that VxWorks on a PC
has a "spurious interrupt" assignment.
Rick "rickman" Collins
Ignore the reply address. To email me use the above address with the XY
Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design URL http://www.arius.com
4 King Ave 301-682-7772 Voice
Frederick, MD 21701-3110 301-682-7666 FAX
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