JK Flip flop skizze

Thread Starter

thexy

Joined Dec 13, 2015
130
JKff.jpg
It's given time course of the inputs. I need to circle is Q 1,0 or not known (unbekannt). Can someone help me with this example?

Mod edit: reduced image size (after WBahn did it below) to reduce loading times.
 
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WBahn

Joined Mar 31, 2012
25,923
It's given time course of the inputs. I need to circle is Q 1,0 or not known (unbekannt). Can someone help me with this example?
Let's first see about getting your image to a reasonable size and orientation:

image.jpeg

Next, you need to show YOUR best attempt to solve YOUR problem.

Take it one step at a time.

For slot 1, do you know what the state of the flip flop is?
 

WBahn

Joined Mar 31, 2012
25,923
I think I misread your intent. I thought you were refusing to answer the question, when in fact I think you WERE answering the question.

That is correct, you do not know what the initial state of the flip flop is.

That's fine -- that's one of the three options available to you. So now go on to step #2.
 

Thread Starter

thexy

Joined Dec 13, 2015
130
I think I misread your intent. I thought you were refusing to answer the question, when in fact I think you WERE answering the question.

That is correct, you do not know what the initial state of the flip flop is.

That's fine -- that's one of the three options available to you. So now go on to step #2.
What is step 2?
 

WBahn

Joined Mar 31, 2012
25,923
The step after step 1. :D

I'm referring to time slot #2 (you already have #1 done and there are a total of 12).
 

Papabravo

Joined Feb 24, 2006
13,958
Q is unknown until the first rising clock edge which occurs in period #5. The value of Q in period #5 depends on the values of J, K, and possibly Q in period #4 according to the work you did on understanding the state machine diagram.
 

Thread Starter

thexy

Joined Dec 13, 2015
130
Q is unknown until the first rising clock edge which occurs in period #5. The value of Q in period #5 depends on the values of J, K, and possibly Q in period #4 according to the work you did on understanding the state machine diagram.
Still don't understand
 

Papabravo

Joined Feb 24, 2006
13,958
  1. When the clock signal (CLK) is HIGH, the output Q cannot change.
  2. When the clock signal (CLK) is LOW, the output Q cannot change.
  3. When the clock signal (CLK) has a falling edge (a transition from HIGH to LOW), the output Q cannot change.
The clock signal has it's first rising edge (a transition from LOW to HIGH), at the beginning of period #5

Therefore Q must be unknown in periods #1, #2, #3, and #4 because it was unknown in time period #1, and it has not changed.
Just before the rising edge at the beginning of time period #5, J=K=1 which means that when the rising clock edge arrives the flip-flop will do what?
Choose one of the following:
  1. Clear to 0
  2. Set to 1
  3. Do nothing
  4. Toggle
If your answer is 1 or 2 then you know the value of Q. If your answer is 3 or 4, then you still don't know and you must proceed to the next step. which time period has the next rising edge of the clock (CLK)?
 

Thread Starter

thexy

Joined Dec 13, 2015
130
  1. When the clock signal (CLK) is HIGH, the output Q cannot change.
  2. When the clock signal (CLK) is LOW, the output Q cannot change.
  3. When the clock signal (CLK) has a falling edge (a transition from HIGH to LOW), the output Q cannot change.
The clock signal has it's first rising edge (a transition from LOW to HIGH), at the beginning of period #5

Therefore Q must be unknown in periods #1, #2, #3, and #4 because it was unknown in time period #1, and it has not changed.
Just before the rising edge at the beginning of time period #5, J=K=1 which means that when the rising clock edge arrives the flip-flop will do what?
Choose one of the following:
  1. Clear to 0
  2. Set to 1
  3. Do nothing
  4. Toggle
If your answer is 1 or 2 then you know the value of Q. If your answer is 3 or 4, then you still don't know and you must proceed to the next step. which time period has the next rising edge of the clock (CLK)?
How I know that in period 5 J and K=1
 

Papabravo

Joined Feb 24, 2006
13,958
How I know that in period 5 J and K=1
You look at the diagram.
  1. In time period #5, J is clearly higher than it is in time period #6
  2. In time period #5, K is clearly higher than it is in time period #3
To me the diagram is showing quite clearly the values 0 and 1, true and false, high and low. What did you think the diagram was showing?
 

Thread Starter

thexy

Joined Dec 13, 2015
130
You look at the diagram.
  1. In time period #5, J is clearly higher than it is in time period #6
  2. In time period #5, K is clearly higher than it is in time period #3
To me the diagram is showing quite clearly the values 0 and 1, true and false, high and low. What did you think the diagram was showing?
Same, but i just started learning flip flops so it's still unclear to me. So J is 1 until period 6 or?
 

Papabravo

Joined Feb 24, 2006
13,958
See post #14 in this thread. The values of J and K just before the rising clock edge determine the value of Q according to the state machine that you analyzed in your previous thread on the JK state machine. I wrote out the behavioral description of what happens when J and K assume certain values. Go back to that previous thread
http://forum.allaboutcircuits.com/threads/jk-flip-flops.118483/page-2
reread what I wrote in post #26, and this time pay attention so I don't have to keep repeating myself.
 
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