# Logic and counter circuit?

Discussion in 'General Electronics Chat' started by electronice123, Feb 7, 2009.

1. ### electronice123 Thread Starter Senior Member

Oct 10, 2008
304
0
I am trying to build a circuit to do the following.

The circuit has a vco which provides a digital input to a counter which counts to 4. Each count turns on a seperate flip flop. I can't figure out how to prevent the counts 1 and 2 from turning on when the counter counts to 3 and turns on the # 3 flip flop.

2. ### AlexK Active Member

May 23, 2007
34
0
Maybe you can make the following logic before entering #2 flip flop:

AND(NAND(Q1,Q2),Q2)

Meaning, if both Q1 and Q2 are high then the input to #2 is always low.
But, if one of them is low then the input to #2 will be simply Q2 because AND(1,Q2)=Q2.

Similar logic can be put before #1 flip flop.

Hope this helps.

3. ### electronice123 Thread Starter Senior Member

Oct 10, 2008
304
0
I tried that, but using those gates a 1 or 2 output from the counter will turn on both 1 and 2 flip flops?

I know there's a way to do this???

4. ### electronice123 Thread Starter Senior Member

Oct 10, 2008
304
0
I figured it out, using an OR and EX-OR gate! Works Perfectly!!!