[sdiy] Funky flip-flops

[David Cornutt]

On Sep 24, 2004, at 1:17 PM, Karl Ekdahl wrote:

> Hi all, i've got a strange problem. I have 8
> flip-flops (4 * 7474) which all share a common ~SET
> line and each have it's ~RESET tied to ground trough a
> 10k resistor.

I'm not totally sure I'm reading this right, but it kind of looks
like you have both the ~SET and ~RESET lines active at the
same time at some point.  On many D-type flip-flops, the
result of this is indeterminate or may vary depending on
the manufacturer.  For instance, I just looked up the Fairchild
74F74, and it says that if you do this, Q and ~Q *both* go high.
If you then clock it, ~Q goes low while Q stays high, which
could add to the confusion.

If you aren't using the ~RESET pins, tie them all to Vcc
through a 1K resistor.