Re: [stella] Adventures in cart building

Subject: Re: [stella] Adventures in cart building
From: "B. Watson" <atari@xxxxxxxxxxxxxx>
Date: Mon, 10 Sep 2001 13:23:42 -0400 (EDT)
On Mon, 10 Sep 2001, Chris Wilkson wrote:

> On Sun, 9 Sep 2001, B. Watson wrote:
> > I've now got a cart board (made of a dead Pitfall cart) that I can plug a 27256
> > The thing looks awful, it's a patchwork of jumper wires and hot glue, I think
> > I'll call it FrankenCart...
> Hmmm...that's what I called my first attempt.  Must be a common name.  :)

If it had a neck, I'm sure there would be a couple of bolts sticking out
of it :)

> > For the bank-switched version... I don't know the standard way to do this, but
> > I have a few 13-input AND gate ICs, and lots of invertors, so I should be able
> > to wire all the address lines to the inputs of the AND gate (and the unused
> > input to Vcc), and invert the appropriate ones, until I have a gate that will
> > trigger when the magic memory location is accessed. Then I need a what, a
> > flip-flop or something, to control the A12 line of the chip?
> This is basically correct.  You'll need some form of register (it doesn't have
> to be a flipflop).  You'll also find (maybe) that you'll need a glitch filter
> for the output of your detector, to avoid false switches caused by asynchronous
> (reletive to each other) address line transitions.  This will be a parts
> intensive board, even for dev purposes.  You might want to consider using
> programmable logic, if you're able.  It will simplify things a lot.

Ergh. I've been planning to learn PIC assembly for a while now.. The roommate
keeps telling me I'm wasting my time with all this 6502 stuff...

After we got the 4k cart working, he went in the other room & locked the door,
and came out a couple hours later with a cart that takes a 32K EPROM and has
DIP switches to select which 4k bank gets addressed by the Atari... so now we
have an 8-in-1 multi-cart, even tho I was wanting to build it myself..

We should be starting on the 8k bankswitched version pretty soon. I remember
getting those 13-input AND gates and wondering, `wtf would this ever be good
for?', now I know :)



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