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Date:      Sun, 02 Nov 1997 11:18:06 -0500
From:      Jerry Hicks <wghhicks@ix.netcom.com>
To:        hackers@FreeBSD.ORG
Subject:   Re: 7400 gates effected by probe routine
Message-ID:  <345CA7BE.B8E3E25B@ix.netcom.com>
References:  <Pine.BSF.3.96.971101231708.2591B-100000@trojanhorse.ml.org> <345C87C9.15FB7483@est.is>

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Þorður Ivarsson wrote:
> 
> I am not sure at the moment but I have been working with Rocwell 6522
> PIA and
> I think it should be possible to probe 8255 in same manner as 6522, send
> byte to
> output ports and read back, if they are defined as output you should get
> the
> same back out from them. I think you can also with the control register.
> 
> Do you have the 8255 datasheet ? it is available from Intel website
> 
> --
> Þórður Ívarsson         Thordur Ivarsson
> Rafeindavirki           Electronic technician
> Norðurgötu 30           Nordurgotu 30
> Box 309                 Box 309
> 602 Akureyri            602 Akureyri
> Ísland                  Iceland
> 
> ---------------------------------------------
> FreeBSD has good features,
> Some others are full of unwanted features!
> ---------------------------------------------

FWIR, you can't read the outputs back from a simple buffered 8255.  We
designed a board once with a registered PAL to front-end the 8255 for
that function.

Good Luck,

Jerry Hicks
jerry_hicks@bigfoot.com



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