Re: Asteroids - VSM woes

I did have what I thought was a good test routine for the Asteroids that
took advantage of the built in self test to generate a stable
Signature...but I really haven't had much time to study this. I'll try to
get around to posting my results so someone else can fine tune it. The
basic premise is that if you can get the machine go into the self test and
it is not firing the watchdog, then the signatures should help point to the
vector circuit that is not allowing the picture to draw correctly. however
there is a lot of feedback that has to work correctly to get the
Start/Stop signals chugging along.

I have too many projects to really study this one right now, but, as I say,
I'll dig up my signatures and post them with the pins. I had a student
spend an afternoon noting the signatures on a good board for all the signal
paths by IC/pin. Have about forty signatures...

John :-#)#

At 02:41 PM 01/05/2002 -0400, Kev wrote:

>This subject has been kicked around for awhile but nothing has really
>developed from this.
>
>An EPROM/Test program probably isn't the solution.
>
>I belive John Robertson had a method of Signature Analysis for this but I
>couldn't duplicate it reliably.
>
>Another approach would be to control the PROM and some how single step the
>VSM but this would require a logic analyzer to actually see what is going
>on.
>
>Kev
>
>
>
> >
> > > These were all due to bad RAMs that had all passed the RAM test.
> >
> > Well, I've now tried replacing all the RAM chips with tested good ones
> > (both program and vector RAM) but it made no difference. Still, I at least
> > know the RAM is fine now. :-)
> >
> > Given the relevant programming skills and Asteroids hardware knowledge,
> > would it be possible to knock up a special test EPROM for, say, Asteroids
> > that not only thoroughly tests the RAM and ROM, but maybe also other
> > components on the board?
> >
> > I should have also said that I know the VSM is causing the constant resets
> > as I clipped pin 1 of the LS42 at L6 (so isolating the VSM) and the game
> > then plays fine (but obviously blind!).
> >
> >
> >
> > Phil
> >
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Received on Thu May 2 22:37:47 2002