Electronic – 4-bit Self-correcting Johnson Counter on D flip-flops

Given the information you have provided, you will have trouble getting the help you're looking for, because you haven't presented enough evidence that you have tried to solve this problem on your own. Listing a 3 bit counter's output isn't enough, as it just shows you can count in binary. What approaches have you tried? Maybe post a circuit diagram of a failed attempt. If you can't do that, then perhaps a better place to start is to ask a different question, specifically targeting the four types of flip flops that you must use.

I'm not trying to come off as some pedantic internet poster, I just want to make sure you get the help you need while still learning the fundamentals that your course is trying to teach you.

For simulation, I can't really recommend anything off-hand since that is not my area of expertise, but I did download LogicSim and it looks useful. I tested a quick SR circuit and it did the right thing -- just make sure you don't leave anything floating.

Here's a list of other free digital logic simulators.

This is a cool assignment! Have fun with it and post up what you've come up with, and I'm sure you'll get the help you need.

A design simplification is to first design the up/down Johnson and ring counters independently. Then just place a mux that selects Q* of either one depending on y.

^{simulate this circuit – Schematic created using CircuitLab}