Re: catbox

From: Philip Pemberton <>
Date: Mon May 12 2008 - 15:16:48 EDT

andre wrote:
> Awesome..thanks for the reply.. Maybe I'll just get
> one and try it out.. for 50$ can't really go wrong.

Get another 6502 chip and a few turned pin sockets if you can... Wire the data
bus lines of the 6502 to the value of a NOP instruction, then connect nRST,
nNMI and nIRQ to +5V. Plug the chip into a turned-pin socket, then plug that
socket into the game board. That'll generate a continuous 0x0000-->0xFFFF
count on the address lines, then wrap around.

There's also a variant of this trick that uses a modified DIL socket with the
various data lines wired high or low to match. Problem with that is that you
need to pull all the ROMs and RAMs (and disable the peripheral hardware in
some way) otherwise you'll get issues with the test results.

If you feel bad about butchering a 6502 chip, get a pair of CMOS 4040
counters, and use them to generate a constant incrementing address. Clock #1
off phi-0-in, and #2 off the most significant output on counter #1. Then add a
pair of inverters to generate phi-2 from phi-0 (wiring: PHI-0 --> INVERTER -->
INVERTER --> PHI-2). That'll catch most of the test cases, but a 6502 chip is
still your best bet if you don't have a Catbox.

Of course, this from the guy who's never debugged an arcade board in his life.
I did spend a few days debugging a homebrew 6502 computer, though, so I know
some of the tricks and time-savers :)

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Received on Mon May 12 16:11:28 2008

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