[sdiy] 4027

[Tim Daugard]

> >>They use a transfer gate D-FF instead of the RS-FF that you seem to
> >>expect, which isn't exactly uncommon in CMOS. This leads to the
input
> >>circuitry shown in the data sheet (check any textbook for the
> >>transformations between different FF types).
> >>
> >>> The ST Micro abortion has a
> >>> J-K input circuit that cannot possibly ever consider the logic
state
> >>> of both J and K inputs being high.
> >>
> >>It can. Whatever was wrong with the '4027 that Tim used it, wasn't
the
> >>data sheet. I'd suspect the culprit with the setup and hold times if
> >>the problem is specific to the ST part.

After checking it, a ST 4027 does toggle. It is extremely fussy on the
size of pull up and pull down resistors. Apparently the resistors were
to large to change the stored charge. I still prefer TTL, but TTL really
doesn't like 12V.

> >Ok, I get this, my problem is of a semantic nature with the way the
> >truth table is presented.  It is my contention that the data sheet
> >should be indicating a dependancy on Q and it clearly does not say
that.
> > It works only when you know enough to assume the dependancy on Q and
I
> >think that's righteously lame.

So do I, that data sheet combined with the wrong sized pull up resistors
(I was using a version of open collector logic with transistors) lead me
to completely change my design.

oh well . . . it's Monday and something actually somewaht worked the way
I expected. Now, if the stock market would work the way I expected, life
would be good.

Tim Daugard
AG4GZ 30.4078N 86.6227W Alt: 3.7 M
http://home.sprintmail.com/~daugard/synth.htm