Re: Battlezone problem.

 Ok, so I tried some of the suggestions folks sent. I reseated the chips
again and checked for bent pins, etc. Still no dice. Forcing the
resetting to stop by grounding that WDDIS testpoint worked, but the game
is still dead. I can assume that taking the chips out and cleaning or
handling the board killed something that was on it's way out (though I am
very careful and have experience working with stuff like this for many
years... strange. Only old games seem to be so sensitive...)

 My question is this: what is the boot sequence of the battlezone board?
  When does the Watchdog clear address get written to by the cpu?

                                        Mitch

On Tue, 13 Jan 1998 jwelser@ccwf.cc.utexas.edu wrote:

>
> On Tue, 13 Jan 1998, Mitchell Rohde wrote:
>
> > Now I get zilch from the unit. I didn't see squat on the data lines, and
> > I heard a "blip-blip-blip-blip..." from the speaker... the sound of a
> > reset. So I probed the reset circuit output, sure enough.. it's
> > going up and down about two or three times a second. If I press the reset
> > switch on the generator board it pins the thing in reset, but when I
> > release it goes back to the resetting...
> >
> > How does this watchdog circuit work, and has anyone seen this before?
> > What trips the watchdog?
> >
>
> Hey Mitch,
>
> Long time no "see."
>
> The watchdog is just a counter that, when it counts to its max.
> value, triggers the reset. There is an instruction (which could be just a
> store to a certian location) which clears the watchdog. So, in theory, if
> the CPU is running properly, it should clear the watchdog timer before it
> times out.
>
> If you've got schematics, there is a WDCLR signal which goes to
> the RESET line on the counter (which generates the RESET line to the CPU)
> probe it and see if it's pulsing at all. If it's not, then there is some
> other CPU problem. There is also a test point on the board labeled WDDIS
> or something like that. If you ground it with an alligator clip lead it
> disables the watchdog counter. The theory goes that if it works with the
> wotchdog disabled, then there is a watchdog problem, else there is a CPU
> problem. My Lunar Lander didn't work (i.e. stayed in RESET) despite my
> disabling the watchdog, and it turned out to be a bad watchdog counter, so
> there's no hard and fast rule....
>
> Good luck....
>
> Joe
>
>
>
>
>
Received on Wed Jan 14 18:21:46 1998