Elenco Understanding Logic Gates and Circuits - Manual (Page 21)

U19
U1 5
Project 13: Gated D Latch
Details of the Gated D Latch Block Diagram and Logic Chart on Next Page.
This circuit demonstrates how a Gated D Latch works. Turn the slide switch (S1) on. Connect one end of the red
jumper wire to the A input of the lower U16 module and the B input of the upper U16 module (this represents the E
input) and connect the loose end of the red wire to 1 (Latch enabled). Connect one end of the black wire to the A
input of the U15 on the left and the B input of the lower U16 module (this represents the D, or data, input). Note that
when you connect the loose end of the black wire to 1, the red LED is on, and when you connect the loose end of the
black wire to 0, the red LED is off. With the black wire connected to 1 (red LED on), connect the red wire to 0. Note
that the red LED remains on now, regardless of whether the black wire is connected to 1 or 0. The green LED should
always be the opposite of the red LED (green LED off when red LED on and green LED on when red LED off) since the
green LED represents Q which is the opposite of Q.
U16
1
U19 U16
1
1
1
1
1
3
2
2
2
2
2
2
2 2
3
2
3
2
D
E
1
2
2
2
2
2
2
3
2
2
2
3
2
3
3
1
4
2
3
3
2
3
2
4
1
3
2
3
4
21
1
0
2
1
3
4 1
2
5
Q
Q
2