Decrementing a four digit counter?
From: Zucker (zuckuss_at_comcast.net)
Date: 08/06/04
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Date: Fri, 06 Aug 2004 18:10:31 GMT
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
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