Re: Decrementing a four digit counter?

From: Geir Klemetsen (ugyldig_at_adresse.no)
Date: 08/07/04 

Date: Sat, 7 Aug 2004 14:35:12 +0200

"Zucker" <zuckuss@comcast.net> skrev i melding
news:rQPQc.21183117$Id.3510468@news.easynews.com...
> I have built a four digit counter using an Allen Bradley photoswitch which
> clocks four 74190s (Up/Down Decade Counters). When the beam from the
> photoswitch is interrupted, the counter counts up.
>
> I would like to be able to decrement the counter manually with a single
> switch and have it act independently from the photoswitch (when
> decrementing, the switch should be the clocking device, not the
> photoswitch). This switch would have to drive the up/down pin AND the
clock
> pin of the 74190s at the same time. It doesn't seem like you would be able
> to control both up/down and clocking operations at the same time due to
the
> propagation delays of the 190s.
>
> Does anyone have any ideas on how I can decrement these 74190s with a
single
> switch?
>
> Thanks,
> Steve

I beleive you have to use a delay circuit. The button itself must be
conected to the up/down pin on the counter directly (no delay circuit
between).
 The delay circuit must stay between the button and the clock-input of the
counter.

Geir