# Synchronous Counter Mod-12 Up/Down Exercise

## Homework Statement

"Design a Synchronous Counter Mod-12 Up/Down, using only Flip-Flop Type D. A binary input ##U## that determines if the counter has to increase (##U = 1##) or decrease (##U = 0##).

## Homework Equations

Flip-Flop Type D equation is
##Q_{t + 1} = D##

## The Attempt at a Solution

I have done already this type of exercise but without the Up/Down. How should it be now? Do I have to add a column ##U## when I write the table? Like for example:
##q_3 q_2 q_1 q_0 | q_3' q_2' q_1' q_0' | D_3 D_2 D_1 D_0 | U##
##0 0 0 0 | 0 0 0 1 | 0 0 0 1 | -##
##0 0 0 1 | 0 0 1 0 | 0 0 1 0 | -##
etc.
And in that column, when do I have to write ##1## and when ##0## since it is up to the one that uses the counter? Or I write all "don't care" in the column? But wouldn't that be pointless?

## Answers and Replies

Nidum
Science Advisor
Gold Member
You could easily find some online help with this .

A search on the obvious ' Up down counter with D flip flops ' returns a lot of useful information .

Please come back if you still have problems .

Kernul