RE: Using a logic analyzer on vector boards

The idea for the Cat Box is to give you much more than just signatures. It
allows you to read out particular addresses in memory as if you were the CPU
(checking all data paths in the process. And push in values to an address
(same deal from the other side).

Along with being able to do something like pull the CPU out of a BZ and push
in a couple of addresses into the vector generator and get a known picture.
The docs tell you just how to put in the "code" for a square on an
Asteroids. This lets you check the entire vector generator subsection with
a very small known good set of signals that have nothing to do with the
rooms or CPU.

Same deal if you are trying to check out any other I/O. You can see the
value as if you were the CPU. Much easier to track the path that way.

Then there is its ram / ROM checking features. Push out a value into a ram
address then read it back. If it gets garbled you can track down just how
and why pretty easy, it does have 4K automatic checks (this could be updated
in a tester in a chip unit).

Or check sum a ROM in circuit. That will tell you for sure if its a
marginal ROM / bad socket / blown '244 etc. I hate fighting a ROM that
check out good in the burner but doesn't seem to work in circuit.

And so on.

In case you couldn't tell, yes I am still very interested in reverse
engineering this unit and building some repros. While there is a lot more
that could be done beyond what it does now it would still be really
valuable.

David

> ----------
> From: jwelser@ccwf.cc.utexas.edu[SMTP:jwelser@ccwf.cc.utexas.edu]
> Reply To: vectorlist@mcfeeley.cc.utexas.edu
> Sent: Thursday, July 02, 1998 8:58 AM
> To: vectorlist@mcfeeley.cc.utexas.edu
> Subject: RE: Using a logic analyzer on vector boards
>
> On Wed, 1 Jul 1998, David Shoemaker (Comforce/RhoTech) wrote:
>
> > So now back to my original message:
> >
> > > I just picked up a HP 1630D logic analyzer (32 channel 400mhz). It
> cost
> > > me somewhere around an arm and a leg :) And now I am wondering if
> anyone
> > > here has used a logic analyzer on vector boards. I am thinking Atari
> > > boards in particular (BZ, Gravitar, Quantum).
> > >
> > > If anyone has used one (on vector or not) I could probably use some
> hints.
> > >
> > > All this because I still can't find a cat box. If anyone has one for
> sale
> > > in the single leg price range (only have one left) I am really
> interested.
>
> Here is my question to the list: Why exactly does anybody
> need a Cat Box? I was talking to Joel in email a few days ago, and
> I found out that you can do signature analysis on the Mathboxes
> without a Cat Box (just jumper some conductors on the test connector)
> with an ordinary 5004.
>
> I've been fiddling with putting CPUs into "NOP mode" these
> past few days, and I see no reason why you couldn't do that to
> troubleshoot the CPU, and then use signature analysis to troubleshoot
> the mathbox (without a CAT box)
>
> I've seen references to using signature analysis to troubleshoot
> CPU boards in nop mode, with Space Invaders, and with Atari boards,
> (of course there's Cinematronics boards, too, but they're a little
> different since the CPU isn't in NOP mode) and I've been fooling
> around with Gottlieb boards and signature analysis.
>
> Which brings me back to my original question. Why does anybody
> need a CAT box anyway?
>
> Joe
>
Received on Thu Jul 2 14:06:24 1998