RE: Tempest resetting problem

Well, I've ruled out the Power Reset and Watchdog counter along with the
clock circuit. I used a logic comparator and tested every chip in that
circuit and they all test out fine.

My roomate seems to disagree with my "it's a ram problem" theory because
if the CPU keeps resetting it will never see the ram.

I do have a question though. There are 4 2114 ram chips which make up the
program ram and about 6 which make up the vector ram. Right? Well, I
tried pulling out the roms as suggested below and looked at the chip
select pins on the ram chips. All the program ram chips stayed high while
all the vector ram chips were pulsing on the chip select line. In fact,
they pulsed at about the same frequency as the reset line pulsed. Could
there be a clue here? hmmm....

By the way - I ordered some of those Braemar tapes for the Fluke 9010a
troubleshooter and they are $16 bucks a piece (yes I also know how to use
the RS232 interface) and they only sell them in packs of 10. I got them
anyway - don't ask me why. Well, whoever can give me a solution that
works for this tempest problem will get a free blank tape on me! Oooh
Ahhh! You don't even have to pay for shipping.

Matt

_____________________________________________________________________

On Mon, 18 Oct 1999, Chris Loggans wrote:

> > ...
> >2) I'm not so sure of the ram. My fluke 9010a can't do a read/Write to
> >anything in the ram address space (both program ram and color vector
> >ram) - so either one of the buffers is bad or a ram chip is bad.
>
> I think this is your best guess right here. If the Fluke cannot reach the
> RAM, then the CPU can't reach the RAM and nothing will work. As you
> mentioned, it could be a buffer issue. It could also be a chip select
> issue. If this is the case, then either the chip select lines are not
> functioning or there is a chip that is stuck "on", regardless of whether or
> not is is selected. Even though you know the ROM's are OK, I would remove
> all of the ROM's and then try to do the RAM test. If the RAM can now be
> reached, then put the ROM's back in one at a time and see when the problem
> re-occurs. You should be able to narrow it down from there.
>
> Good luck,
> -Chris
>
Received on Tue Oct 19 05:23:26 1999