Hey guys, I have to do a 6-0 down counter and a 12-1 down counter, the thing is, I have no idea how to do the 6-0, and for the 12-1, I only know how to do 1-12 up counter. Screenshot below of 1-12, is there anyway I can reverse this? As for the 6-0, how can this be done? I need to use D flip flops and nand4 gates. A drawing or screenshot of this done in a simulation would help a lot.

 

I have one in front of me but don't know how to get it up here. So if you look up diagrams for "Reversable Johnson Decade" I'm sure that is what your after. A great source for old TTL logic circuits is "Guidebook of electronic circuits" by John Markus..if you can find a copy. GL

 

Take a look at this page of the AAC e-book:
http://www.allaboutcircuits.com/vol_4/chpt_11/3.html

Build the down-counter of your choice. Afterwards, you should have it load the number 6 every time it reaches 0 and underflows (at 15 essentially).

The same operation stands for the 12-1 counter, but you will have to load 12 when it reaches 0.

Is that clear?