# Digital Electronics: State machine

by 6021023
Tags: circuits, state machine
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 P: 90 1. The problem statement, all variables and given/known data (a) How many states does this system have? (b) How many rows will there be in a state transition table? (c) Provide the state transition table. (d) Draw a state diagram of the system. (e) Describe what the circuit does in words. 2. Relevant equations 3. The attempt at a solution a) I think there are two flip flops (or are they switches?), so that means that there are four states: 00, 01, 10, and 11. b) I think the state transition table will have 8 rows. These numbers will be at the beginning of each row: 000 001 010 011 100 101 110 111
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P: 41,353
 Quote by 6021023 1. The problem statement, all variables and given/known data (a) How many states does this system have? (b) How many rows will there be in a state transition table? (c) Provide the state transition table. (d) Draw a state diagram of the system. (e) Describe what the circuit does in words. 2. Relevant equations 3. The attempt at a solution a) I think there are two flip flops (or are they switches?), so that means that there are four states: 00, 01, 10, and 11. b) I think the state transition table will have 8 rows. These numbers will be at the beginning of each row: 000 001 010 011 100 101 110 111
Good. Correct so far. Now make label those three columns as A, B and Y (the inputs to the logic), and make 2 more columns for the "Next X, Next Y" outputs of the FFs. Use the logic terms shown for the J&K inputs for the 2 FFs to calculate what the Next X and Next Y outputs will be for each row. That is your transition table. Then use that to answer the rest of the questions.

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 P: 90 A B Y Next X Next Y 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 I'm a little bit confused as to what to do after this. I see the equation AB'Y + A'BY' going into J and K. So that means that J and K will always be the same. Is that right?
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P: 41,353
Digital Electronics: State machine

 Quote by 6021023 A B Y Next X Next Y 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 I'm a little bit confused as to what to do after this. I see the equation AB'Y + A'BY' going into J and K. So that means that J and K will always be the same. Is that right?
Yes, from the diagram, it does appear that J and K for each FF are the same. What does a JK FF do when both inputs are the same?
 P: 90 When both J and K are 0, then there is no change in outputs. When they are both 1, then the outputs are toggled. A B Y Next X Next Y 0 0 0 I still get stuck at this part. I can tell that next Y is going to be 0, but I can't say what next X is, because the table doesn't tell me what X currently is. Another question. Is the circuit a Mealy machine, since the output is going back into the input?

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