# mod 6 up down counter

Discussion in 'Homework Help' started by magik5, Oct 2, 2008.

1. ### magik5 Thread Starter New Member

Oct 2, 2008
3
0
Hello all,

I have to design a mod6 counter. It counts up (1) and down(0) with the throw of a switch. I was given a mod5 counter to help implement this.

I'm stuck on actually implementing this in MMLogic. I have a constructed truth tables and an excitation table for this counter. I am using 3 JK FF, and In modification of the mod5 counter, I know this.

From 4 (Q2-1,Q1-0,Q0-0) to 5 (Q2-1,Q1-0,Q0-1) I need Q2=Q(no change), Q1-Q(no change), and Q0-1(set to one), which means J must be 1 and K don't care.

Then when it hits 5(101) I need to pass all 0's so I can reset to 0 and continue counting up.

Does this just mean that I need to have the middle OR gate connected to the 2 AND gates, have 3 inputs too?

i have attached the mod5 mmlogic picture.

Any help would be appreciated.

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2. ### magik5 Thread Starter New Member

Oct 2, 2008
3
0
I have continued to work on my problem

Here's is what i have come up with.

With what I have here it counts up all the way to 7 (111) then back to zero. I am supposed to get it to stop at 5, and then reset to 0. And it does not count down at all....

am i not thinking logically ? I guess not, any help would be appreciated.

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3. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
The difference between a mod 5 and -6 counter is where the bits are sensed to halt the count. 5 in binary is 101, 6 is 110. Look at how the mod 5 works, and imagine how to make it do mod 6.

4. ### magik5 Thread Starter New Member

Oct 2, 2008
3
0
Oh I am trying so hard to think....

I know that when I count up to 4(100) my next state is 5(101).

So in order to make that happen I must deal with Q0.
I know my JK FF is J-1 K-Dont care from my exciation table.

I'm just not sure how I can change J0 during a cycle without messing up my count...

Thanks for your input - I will be trying to implement this all night.