hope you are all well. I have an homework which wants from me something like this:
Design a counter that counts 0 4 6 8 12 14 0... (mod6) and when to counter shows 14 it is going to stop and wait for 3 minutes. After 3 minutes counter is going to count 0 1 2 3 4.... 14 15 0 ... There is going to be 6.667 seconds between every count. (You need to use JK Flip Flops to do so.)
So far I tried to find what each J and K input of the Flip Flops should be in order to achieve the sequence. I made table which looks something like this below:
I only wrote 6 rows because I am tasked to show only 6 numbers. Q' represents the configuration of Q outputs for numbers 0 4 6 8 12 14. J(0:3) and K(0:3) represents the configuration of the J and K inputs to change the corresponding Q outputs in each state.
I then drew Karnaugh Maps to find the equivalent logic expressions for the J and K inputs. Here are what I have come up with:
J3 = Q2 + Q1.Q0 K3 = 1 J2 = Q1'.Q0 + Q1.Q0' K2 = 0 J1 = Q2.Q0 K1 = Q0 J0 = 0 K0 = 1
Then I designed the circuit. The fact that J0 = 0 made me sceptic about the functionality of my circuit; however I still gave it a chance (I checked my table and my Karnaugh maps twice, if I haven't overlooked any detail the tablo and Karnaugh's must be correct.) I simulated my circuit but counter does not increases, it is stuck at 0. I believe that it is because of the jact that J0 is 0. But this is what I found with the calculations I done. Is there some point I am missing? Or should I try a different approach?
And I want to ask something more. I am assuming I completed this part. What I should I do next to change the sequence of the counter back to normal (0-1-2-3-4)?