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 :) Brian --- If a trainstation is the place where trains stop, what is a workstation? - Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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