State diagram for JK-flip-flop

Your instinct is correct - assign labels to the FF outputs, e.g., Q1 and Q2. To form a state table, on the left side, list the the four possible states of Q1, Q2; on the right side, write the values that Q1 and Q2 will assume after the next clock pulse. The table will then contain a complete description of the state machine.

This looks like a homework question, which I won't answer. But here are some pointers:

• You cannot represent more states than what you have available -> that means that you will have to go to the next higher state (i.e. 2 FF's for 4 states) or use only one FF per state. (i.e. FF #1 correlates directly to A).

• option #1 ( 2 FF's and 4 states) is more economical but you have to make sure that the unused state does n't not get activated and then locks out.

  • you might draw this as a 4th state "D" with loops back to itself.
  • what is generally considered safe design is that you always have explicit transitions AWAY from the unused state in case it gets activated.

• option #2 uses more FF's but cannot have any hidden states.

  • it is inherently safer.
  • it is known as a "one hot" design and thermometer codes are examples of this.

Your choice of states "A = 00" etc. will make the design simpler or more complicated. SO may want to go with what you decribe or you may want to go with state C = "10". You should look at all possibilities.

The first SM, only uses 0 or 1 as an input because it only has one input variable. They should have used a variable for clarity anyways. You'll notice in the table that it is marked as "x" but not in the diagram.