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up / down counter

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elieone

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i'm pretty new to making circuits; i just want to ask how to make an up AND down counter [ counts up then down ] and an n-counter [ 0, 1, 2, 3, 4, 5, 0, 1, 2... ] i already made an up counter and a down counter [see below].

i tried making a switched up/down counter by modifying one of these two circuits: Q'+QX where the Q's are those from a JK flipflop and the X is the switch indicating an up or down counting. the down count works perfectly fine, but when switched to an up counter, it counts 1 , 3 , 7 then F; and it doesn't go back to a lower count either.

i forgot to mention that we were allowed to use 74190 IC's but i'm clueless on how to use them. :(

here are the up / down counters:
 

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Have you looked at the 74190 data sheet? It seems pretty straight forward. It counts up or down depending upon the logic level of the U/D (up/down) input. You can also preset an aribitrary number into the counter using the parallel inputs and the Load input and then count up or down from that number.
 
It's pretty easy to make an up/down binary counter.

What you need is:
1: Any number of toggle flip flops. It's usualy jk or d-flip flops with pulse triggered clock input.
2: Between each toggle, there should be three nand gates that makes a two input multiplexer that shift between the last toggles Q and not(Q) outputs to the next toggle flipflop.

A rough scematic is posted.
 

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