Concerning your sine wave question, you didn't tell me the DC level,
and I don't know that the inputs to the comparator are doing, so it's hard to
say what that might mean. It could mean that you are not providing a good
ground to the scope and nothing more. 50mV is not enough to change a 0 to a 1
so the CPU will ignore it if the DC level is correct. Knowing the frequency of
the sine wave would really help to understand why it's there. If it's 60 Hz,
that's one thing. If it's 10 MHz, that's something else.
As I said before, I don't know why anyone would use a logic probe if they have
an oscilloscope. You would just be removing what could be useful information.
I can't say for sure that the 8048 is good, but if I had to simply guess based on
previous experience, I would say that it probably is fine.
Did you try using the test switch? If the CPU reacts to a change in that switch,
then that would tell us something. Also, turning that switch on puts the code into
a fairly tight loop, which might enable testing some other things.
What do you have on pin 32 of the MCU? Is there any sort of pulse on it?
(With the scope, not the logic probe)
Bob
--------------------------------------------
On Sun, 7/3/16, noddyspuncture@hotmail.com [PolySix] <PolySix@yahoogroups.com> wrote:
Subject: Re: [PolySix] Another P6 with all LED's lit....
To: PolySix@yahoogroups.com
Date: Sunday, July 3, 2016, 10:06 AM
Yes Bob... pin 4 Reset is sitting 'high'
(according to my logic probe) and I also measure 4.85v on it
... I can do the procedure successfully - adding the 56K
resistor, setting VR1 so reset is just 'low' and
when I remove the resistor it then jumps to
'high'.
All that
works... so would you then say that my 8048 processor is
good?Could the MCU be getting stuck because
it's faulty or would another fault elsewhere cause
that?Should I
be looking elsewhere do you reckon?
I am seeing a sine wave of
about 50mV on 'T0' - 8040 pin1 - that's not
right is it?
Cheers,Tom