[sdiy] moog module designs

[Neil Johnson]

Hi,

Scott Gravenhorst wrote:
> Thank you, Tim.  I guess it's something to be aware of.  I went to 
> their
> site and tried to look up 4027, but it doesn't seem to be there.

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

say exactly what happens for J = K = high, i.e., it toggles.

> 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
> implementation?  Either way, that's pretty brain dead.

Either way, the truth table is correct (for a J-K flip-flop).  As for 
the implementation...

Perhaps the chips in question are faulty?  One zap from an ungrounded 
finger can kill a CMOS chip.

Cheers,
Neil

--
Neil Johnson <http://www.njohnson.co.uk>