Experiment 6 - The Gated D Latch (DE Latch)

How can you give the D latch its memory back? To do this you are adding the ENABLE input of the circuit.

The ENABLE is added to the D latch as shown in the circuit diagram. Simular to the RS-E latch in experiment 4, it changes the behaviour of the latch...

Circuit Diagram Gated D Latch.

Symbol Gated D Latch in Circuit Diagram.

• As long as E = 0, the latch is open and you switch between the two results back and forth using D .
• As soon as E = 1, you close the latch and the last result is stored. Now the D input no longer influences the result........ until E goes back to 0.

Circuit of a Gated D Latch. (Enlarge)

Try this out a few times with the circuit shown. Although you introduced the E input as a stopgap, from now on it plays a central role. In the next experiment, you begin to understand why.