Re: ROMs replacement

From: Gerrit Heitsch <>
Date: Mon, 17 Sep 2012 19:00:45 +0200
Message-ID: <>
On 09/16/2012 10:01 PM, Mike Naberezny wrote:
> Hi Spiro,
> On 9/16/12 12:48 PM, Spiro Trikaliotis wrote:
>> Note, this has already been done in the 64'er (I cannot remember the
>> exact issue, though).
> It's in the file here:

Yes, but that is an output only setup. But since it includes the whole 
decoder stage, it should be easy enough modify it to hook up a 6520 or 
6522 in a way that one of the ports has its DDR appear at $0000 and the 
data register appear at $0001, thus giving you the full 8 Bit in both 
directions. The rest of the logic and the other port will be lost 
though. Would be nice as a replacement for a 8501 as well. :)

You will also need the '245 to give the 6502 the ability to tristate the 
address lines. Not sure if you really need the '245 for the data lines, 
I thought those are tristate in the 6502 already, but it can't hurt.


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Received on 2012-09-17 18:00:05

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