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# Experiment 16 - The latch II

Consider the circuit diagram shown. You recognize the RS latch and the extension. The extension avoids the undefined state (R=1, S=1). Also the inputs are renamed to D and E, where D stands for "DATA" and E for "ENABLE".

 D E Q Q' 0 0 0 1 1 0 1 0 0 1 stored 1 1 stored

Truth Table DE Latch.

Circuit Diagram DE Latch.

Also the truth table has changed...

• If E is set to 0, you can use D to switch freely between Q and Q'... Q follows D. Q' shows the opposite result.
• If E is put to 1, the circuit stores the last value of Q and Q'.
 Circuit of a DE Latch. (Enlarge) Image now, you want to store a piece of information (D). For this you swiitch E to 0, you enter the information by using D and put E back to 1. Now your information is stored. Flip flops are very versatile and can be found in a variety of digital applications. But more about this in other topics. For the moment this was the last experiment on this topic...