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

#### eddiehh

Joined Jun 25, 2016
1
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 ???

#### Papabravo

Joined Feb 24, 2006
20,600
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.

#### Techno Tronix

Joined Jan 10, 2015
139
Read and understand some basic tutorials for jk flipflop, truth table and the parameters which mention by papabravo.

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088
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)

#### Papabravo

Joined Feb 24, 2006
20,600
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)
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?

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088
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.

#### Papabravo

Joined Feb 24, 2006
20,600
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.
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}