# 3 - bit Counter (repeat after each 6 clocks)

I have tried to make a counter which counts until six clock cycles and then repeats. And would like to know whether I have done all right and the counter works correct.

simulate this circuit – Schematic created using CircuitLab

• Want to know if it works ? Simulate it ! Either with Circuitlab (link under your picture above), no idea if that would actually work, never tried it. Or use a program called "qucs" see: qucs.sourceforge.net . Learning to use a simulator is an essential skill any electrical (design) engineer must master. It's not that hard. Jun 7 '15 at 17:23
• I don't have the material. Jun 7 '15 at 17:24
• You can download it for free ! Let me tell you, when I was a boy (in the 1980s) I could only dream of just downloading a free circuit simulator that actually works. It's so much easier these days. Enjoy that is my advise :-) Jun 7 '15 at 17:30
• Yes that is correct. Have fun! Jun 7 '15 at 18:10
• This circuit is not correct. First you need to label your outputs, otherwise we can't check for correctness (Q0, Q1, Q2). Let's take FF3: If it stores zero -> Q=0 and /Q=1. So T3 (T of FF3) is 1. In the next cycle it inverts Q to 1 and /Q=0. So T3 becomes 0. FF3 will never toggle again, because there is no other way to drive T3. Jun 7 '15 at 18:45

## 1 Answer

Sorry, but not close. At a start, FF1, which I presume represents your lsb, should have its input tied to a logic high. I suspect that you intended FF3 to be the lsb, and that you have confused T flip-flops with D flip-flops. Try replacing your FFs with D-types.

• Actually there were only D-flip-flops on the instruction I have followed, but I have chosen T-flip-flops because I found D flip-flops without their inverse Q' in the simulator. Jun 7 '15 at 21:46
• Then add an inverter to the Q output to get a Q' output. And for heaven's sake, learn the difference between T and D flip-flops! Jun 7 '15 at 22:11
• I did invert them. And Thank you for correcting me. Jun 7 '15 at 23:34