Re: PC as 1541

From: Spiro Trikaliotis <ml-cbmhackers_at_trikaliotis.net>
Date: Thu, 28 Apr 2011 21:28:05 +0200
Message-ID: <20110428192805.GF21751@trikaliotis.net>
* On Thu, Apr 28, 2011 at 12:21:43PM -0700 Steve Gray wrote:
 
> ----- Original Message ----
> > From: Spiro Trikaliotis <ml-cbmhackers@trikaliotis.net>
[...]
 
> Could you not connect both ATN and DATA to the regular IO lines, but also to the 
> input of an OR GATE, which is then fed  to the interrupt line? The IRQ triggers 
> and you check the regular IO lines to determine which line fired,

That is what I tried to tell you (every reader, that is) with: 

> > However, then we would need another input line (to distinguish ATN
> > and DATA), which we do not have.

There simply is no additional line you can connect the ATN IN to.  Note
that we would also need an additional line for DATA IN, as the current
DATA IN line would be blocked by the "logical OR" of DATA IN and ATN IN.

We do not have that much input lines. That's a limitation of the
parallel port.

Of course, we could add multiplexing to the picture... No, just kidding.

Regards,
Spiro.

-- 
Spiro R. Trikaliotis                              http://opencbm.sf.net/
http://www.trikaliotis.net/                     http://www.viceteam.org/

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Received on 2011-04-28 20:00:26

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