Building a 20-output counter

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Doktor Jones

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Hi, I'm trying to figure out the easiest way to build a 20-output counter... my clock pulses will be coming from an external source, so that's taken care of.

I'm most familiar with 4017 counters... would it be easiest to just chain three together and tie the 21st output back to reset, or is there an easier way to get 20 incrementing (and looping) outputs?
 
If you cascade two 4017s, they naturally count up to 100 before beginning the sequence over again. That means that two outputs are active at the same time (one from the first counter, and one from the second).
 

I am not sure what you are asking or wanting to do? If you cascade two 4017 decade counter divider chips you have a 0 to 99 counter and if you cascade three you have a 0 to 999 counter. To cascade the chips you take the Carry Out (pin 12) of the first chip and run it to the Clock In (pin 14) of the next. Each positive clock transition advances (increments) the count up one. So after ten clock pulses the carry out increments the next counter up one. The first counter would then count 0 through 9 and again increment the next counter up one count.

You can set it up to count to N and halt or count to N and recycle. So with 3 cascaded 4017 chips you can count to any number between 0 and 999 and either halt or recycle.

I guess I don't get the "20 output" thing?

Ron
 
LTX71CM said:
What about something like this?

Wouldn't you have to clock the 4017 from the Qbar output of the 4103? Or use CountEnable on every other clock? That way, the 4017 stays in the same state for two clocks before advancing...
Click to expand...
 
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