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A 4bit counter that goes and down


New Member
Hello everyone,
I am kinda new to the website, I just came across it after looking for answers for such a long time.
I have an assignment that asks to add an input bit to your circuit from the circuit I created that goes up my sequence of 3 up to 15 called U (for up). If U is a 1, your circuit should count up through the sequence of multiples of 3 as normal. If U is a 0, your circuit should count down through the sequence of multiples of 3 (0, 15, 12, ..., 6, 3, 0, 15, 12...). I was able to draw the truth table and the K maps both for going up and down but I don't know how to implement the input circuit. For this assignment, we use a program called Logisim. Please redirect me if I am at the wrong subforum or if any extra information is needed.

This is for going UP


This is for going down



Active Member
What should be Your input clock source?

A free running oszillator? Look for NE555 or C-Mos 4060.

Or an other Source with should be decoupled from this cicuit? Look for Optocouplers.

A simple switch - Then You need a debouncing cicuit.

Or a relay contact - That needs debouncing too?

Today I wanna Do Your Cicuit with a little Microcontroller.
But that has to be programmed.


Well-Known Member
a quick trick would be to invert at the outputs of the filp flops ... or use the !Q pin if its there

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