Trigger Logic

How do you start a counter with a switch (trigger)? How do you de-bounce a toggle switch? How do you stop the counter after one firing cycle is complete?

This circuit gives a solid "on" to allow the 8-bit counter to run.

When switch is pressed, the J input goes high, allowing the JK flip-flop to be set. Then the J input is ignored until the flip-flop becomes reset again. It will become reset when the K input goes high, which will happen when the last comparator detects the end of the whole cycle. This stops the 8-bit counter, until the switch is pressed again.

Note there's one slight flaw (feature?) in this trigger circuit. It allows the 8-bit counter to keep running as long as the trigger switch is held closed.