Experiment 26 - The Gated JK Latch

The JK latch oscillates in the J = K = 1 state and thus has no practical use. But how can you prevent the oscillation...?

In the circuit diagram shown, you recognize the JK latch, which has been extended by one ENABLE (E) input...

Circuit diagram gated JK latch.

• For E = 0, the latch is open.
• For E = 1 the latch closes and the last result is stored.

Circuit gated JK latch. (Enlarge)

However, the "Race Condition" of the JK latch remains. With J = K = 1 and E = 0, the circuit oscillates. Therefore, you can not predict the outcome of Q and Q with E = 1.

You need a circuit in which the latch switches precisely once at a certain point.

For this you use a so-called master-slave circuit...