Didn't you mention having an oscilloscope? If so,
why would you use a logic probe? The scope gives
you a lot more information if you know how to interpret it.
When the MCU is converting voltages, it executes a
"successive approximation" routine. This involves stepping
through each bit of the 8-bit digital value and then looking
at the comparator output to see if that bit should be 1 or 0 in
the digital result. This is done at CPU speeds, so the waveform
on T0 should be toggling between high and low at a high rate
as the mcu is constantly scanning the front panel, or at least
it should be. BTW, isn't it annoying that the Yahoo mail font
changes zeroes to look like an o.
It seems that your MCU may be getting stuck somewhere in
the code. It may be waiting for something that never happens,
in which case the DB0 and 3 values you see may be correct
for that piece of code. Is the reset signal sitting at a high level?
It should not be pulsing low.
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, 7:23 AM
Many thanks for that Bob,
So let me get this right - when
turning front panel controls I should be seeing either 0v or
5v on 'T0'- pin1..?
I am getting no waveform on R37, the
input to IC6 - which I think is wrong.
One other thing I forgot to mention
is that on the 8048 DB0 - DB7 lines, my logic probe shows
activity on all - except DB0 & DB3 (pins 12 and 15)...
would you expect to see this...?
Cheers,Tom