Master-Slave JK Flip-Flops
The JK operates as an SR flip-flop whose inputs are assigned J = S and K = R.
However, whereas the S = R = 1 combination is not allowed, the JK uses this special case to incorporate a very useful mode of operation.
The additional feature of the JK device is that it state toggles, that is changes from 0 to 1 or from 1 to 0 when J = K = 1.
Examination of the state diagram, shown in Fig. 6.25b, indicates that the JK flip-flop will change from the 0 state to the 1 state with an input of J = 1 and K = 0 or J = 1 and K = 1 (toggle).
This means that a logic 1 on J will force the device into the 1 condition no matter what value is placed on K. So K is a don’t-care in this case.