[sdiy] moog module designs

[Tim Daugard]

> fact any REAL JK flip flop can be wired as a D), so why not just use a
> real D flip flop?  They seem to have specifically designed this to NOT
> toggle as a normal JK can.  Since this was deliberate, Tim's mistake
was
> not in abusing the device with static shocks, rather it was buying
from ST
> Micro...  Umm, my condolences, and hopes you didn't buy many.
>
> NOTE: Avoid whatever their engineers were/are smoking...

I solved the problem for the design by hooking the Q not output to the J
input and ignoring the K input. BUT if I wanted an edge triggered D type
flip-flop I would have bought an edge trigered D type. Silly me, I
assumed a J/K flip flop would work as a J/K flip flop.

> -- Scott (who doesn't have ST Micro 4027 ICs and is damned happy)

Tim -- Who does have them, but not a lot. Most of them are being used as
S/R flip flops.

> >
> >The HCF4027 is on the ST website:
> >
> > http://www.st.com/stonline/books/ascii/docs/2039.htm
> >
> >> Interesting that they didn't have the "J and K high" condition in
their
> >> truth table.
> >
> >In a way they do --- the 'X' refers to "don't care"... so the lines
> >
> >J K Q -> Q Q'
> >H X L H L
> >X H H L H

Thats what bit me. If J is high the IC doesn't care what K is at, its
going to put a high out the Q output. And since the Q not is just an
inverted copy the J latch and Q instead of a true K  latch, it doesn't
work as a J/K. (Verified by bench test during a design process.) This is
an explanation of why sometimes it takes me more than a week to create a
new design. It took me two days to convince myself that it wasn't my
knowledge of electronics that was wrong, but the IC. Try troubleshooting
a design using a "standard part" from one manufacturer and using the
data sheet from a different manufacterer. This means that I'll have to
expand my lab IC notebook to include datasheets for multiple versions of
standard parts. And my wife wonders why I don't want to work electronics
proffesionally anymore.

> >> So here's a chicken and egg thing: Did they create the
> >> truth table (incorrectly) and then get engineers to design this or
did
> >> they muff the design and then publish a truth table that shows the
> >> chip's

I suspect it is a feed back trace on the die missing and the truth table
was revised to match the chip. The J/K truth table has been around since
the 60's. What company would create a new truth table for a standard
function? . . . uh never mind ;-(


and as a further aside; I missed a promotion in the US Air Force one
year by 1/2 point. I had a question thrown out from the promotion test
that year that would have given me the one point advantage. The Air
Force had copied the function schematic for a counter chip to the test,
gave you a current state of the chip and the inputs and said what will
the output be. I knew the answer they were looking for, but a roughly
25% pay increase was riding on that test (and other factors). I very
carefully traced through the chip schematic to determine the output of
the chip and realized that the chip as drawn would not provide an output
to match any of the answers. I answered the answer I thought they
expected, and challenged the question. Two months latter I got a reply
back that the drawing had been copied wrong and that question would not
be scored for anyone. 5 months latter I got my promotion score sheet and
had missed by about .5 - I never challenged a question again. Why should
I give the people who guessed at that question a 1 point advantage.