# I have problems understanding the JK and SR flip-flops ...

Discussion in 'Digital Circuit Design' started by eddiehh, Jun 25, 2016.

1. ### eddiehh Thread Starter New Member

Jun 25, 2016
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I have an exam and I need some help ... What are the inputs for a JK flip-flop to have an output like this : Q+ = 001101011
What are the inputs for a SR flip-flop to have an output like this : Q+ = 110001001 ???

2. ### Papabravo Expert

Feb 24, 2006
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The solution to the problem for the JK Flip-flip is not unique. There are four things it can do:
1. CLEAR to 0
2. SET to 1
3. TOGGLE to the opposite state
4. HOLD the present state
So the sequence {CLEAR, CLEAR, SET, SET, CLEAR, SET, CLEAR, SET, SET} would satisfy the requirements of the problem. So would the sequence {CLEAR, HOLD, TOGGLE, HOLD, TOGGLE, TOGGLE, TOGGLE, TOGGLE, HOLD} and there are doubtless many more valid sequences of input that will produce the desired output.

BobaMosfet likes this.
3. ### Techno Tronix Member

Jan 10, 2015
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Read and understand some basic tutorials for jk flipflop, truth table and the parameters which mention by papabravo.

4. ### KeepItSimpleStupid Well-Known Member

Mar 4, 2014
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It sure can't be 1 FF. It has to be a bunch of them.

But J-K can have two answers. (toggle and using J or K)

5. ### Papabravo Expert

Feb 24, 2006
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1 Flipflop CAN produce a string of arbitrary bits on successive edges of the clock. Where did you get the notion that "It sure can't be 1 FF". I thought your desire was to keep it simple; was I misinformed?

6. ### KeepItSimpleStupid Well-Known Member

Mar 4, 2014
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A FF has TWO outputs Q and NOT Q. 001101011 has 9 binary states. How can a device with two states produce 9 binary outputs which is how I read the question. If the output was 0 0 1 1 0 1 0 1 1 I may have interpreted the question differently.

7. ### Papabravo Expert

Feb 24, 2006
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So you made up the rule that whitespace is significant in a string of binary digits. You must not be familiar with regular expression or state machines. Your reasoning and your posts lack credibility.

For the SR FF the input sequence, assuming S and R cannot both be true simultaneously, to produce Q+ = 110001001, would be {SET, SET, CLEAR, CLEAR, CLEAR, SET, CLEAR, CLEAR, SET}

8. ### KeepItSimpleStupid Well-Known Member

Mar 4, 2014
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I guess I do better over here with the highest ratings?

http://www.electro-tech-online.com/members/?type=positive_ratings

Feb 24, 2006
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