# Solving Mod 13 Ripple Counter with D Flip Flop

• d_b
In summary, the problem at hand involves building a ripple counter, specifically an up counter with mod 13 using D flip flops. The state diagram was first constructed, going from 0000 to 1101 and back to 0000. The textbook suggests using the complement of the output from the D flip flop, but this method does not allow for the counter to go from 1101 to 0000. Other attempts were made using k-map and formulas, but none were successful. The issue remains unresolved, and the individual is seeking assistance in constructing the flip flops correctly. This is not a homework problem, but a review question for an upcoming exam.

## Homework Statement

I'm working on this problem but everytime I tried to walk through my answer it doesn't seem right.

I wanted to built a ripple counter, up counter with mod 13 using D flip flop.

## Homework Equations

present state ABCD - 0000-->1101
next state ABCD - 0001-->0000

Q(t+1) = Dq

## The Attempt at a Solution

I first built the state diagram going from 0000 to 1101 then back to 0000.

Now the textbook said to use take the compliments of the output from the D flip flop. So what I did I took the compliment of the output(next state) and the unused state (14 and 15 as don't care) and by k-map i constructed a formula for the 4 D-FF. However as soon as I hit 13(1101) it will not go back to 0000.

The other approach is: I took the output from the next state and the unsued state(1110 and 1111 as don't care states), using k-map again i constructed a formula for the sum of product of the 4 D-FF. But agian it will not go from 1101 to 0000.

Then I redo it by using complements output of the next state with k-map to built the formula for the FFs without the unused state and it still doesn't work.

I redo it agian by using output of the next state with k-map to built the formula for the FFs without the unused state and still doesn't work.

I know that I'm doing something wrong during the process, however I'm not sure howelse to built this FFs.

oh...this is not a homework either, its my exam review questions...