RE: Tempest resetting problem

        There is a very high probability that you have a RAM problem.

        Also, have you tried doing a Bus Test with your Fluke?

        Almost ANY chip in the Microprocessor, Address Decode, RAM, etc,
etc circuit can cause a WD reset problem. I think you said you weren't
able to write to RAM using the Fluke. That is your clue. Most likely you
hav eeither an address decode problem, or a write-enable generation
problem.

        Watchdog problems suck, in general, but it looks like yours has to
do with a RAM or RAM interface problem.

Joe
 
On Tue, 19 Oct 1999, Matt Rossiter - Verio Southern California wrote:

> 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
> >
>

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Joseph J. Welser jwelser@ccwf.cc.utexas.edu
Design Engineer -- Crystal Semiconductor Corporation
Ph.D. Student in E.E. -- University of Texas at Austin
Work: jwelser_at_crystal.cirrus.com http://www.crystal.com
P.O. Box 17847; Austin, TX 78760
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Received on Tue Oct 19 07:58:57 1999