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# Asynchronous down counter help please

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1. I need to design a modulo 6* d type asynchronous down counter in which gated outputs reset the bistables after the appropiate count is achieved.
The drawing shows a three stage counter which i can modify.
A modulo 6* needs to count down 5,4,3,2,1,0 then resets back to 5,4,3,2,1, 0 etc
I can get it to start at 5 and count down to zero but it always resets back to 7.
Thanks
2. Mechynick

I also have this same question but am struggling to get a count. Do I need to edit simulation settings? My waveforms start at 0 then count down from 7. Also, do I need to alter period settings (currently 2ms) Any help would be appreciated.

Thanks
3. leave circuit as is, connect not Q (QN) outputs to a 3 input nand gate whose output will be 0 when all QN outputs are 1 (count 7) is used to SET flip flop U2 back to 1) (set input shown as triggered on negative edge 1 to 0, so u2 Q =1,QN goes to 0, giving count at QN outputs 101 =5, count now repeats endlessly modulo 6 (5,4,3,2,1,0 repeat). Down count taken from QN outputs count out
4. Hi Eric what do you mean by "Set input shown as triggered on negative edge 1 to 0" I have the same question and can't get the curcuit working unless I put a Not gate on U2 and connect two of the Nand gate inputs to the not gate of U2 and the output of U2 which does not make logical sense. Thanks
5. Here are some ideas to get you started, when I worked through it as you can see its hand written and instead of Q1,Q2,Q3i have used Q0, Q1, Q2 hope this helps.
Attached Images
6. asyncdncounter1.pdf (649.7 KB, 22 views)
7. asyncdncounter2.pdf (131.7 KB, 17 views)
8. (Original post by eric reed)
Here are some ideas to get you started, when I worked through it as you can see its hand written and instead of Q1,Q2,Q3i have used Q0, Q1, Q2 hope this helps.
9. Did you get this to work....I can get it to count from 6 to 1 but not 5 to 0
10. Hi eric, if you get a second, would you be able to post a copy of your final p spice circuit drawing, I appreciate your time, thanks in advance.

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