Elenco Understanding Logic Gates and Circuits - Manual (Page 19)

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Project 12: J-K Latch
This circuit demonstrates how a J-K Latch works. Turn
the slide switch (S1) on. Connect the loose ends of
the red and black jumper wires to either 0 or 1.
When the red jumper is connected to 0 & the black
jumper is connected to 1, then the red LED will be
off (J=0, K=1 resets the output to 0)
When the red jumper is connected to 1 & the black
jumper is connected to 0, then red LED will be on
(J=1, K=0 sets the output to 1)
When the red & black jumpers are both connected
to 0, then the red LED will stay the same
• Try starting with the LED off (J=0, K=1) and then move the
black lead to 0 (K=0) to see that the red LED stays off
• Try starting with the LED on (J=1, K=0) and then move the
red lead to 0 (J=0) to see that the red LED stays on
When the red & black jumpers are both connected
to 1, then the red LED will toggle between on & off
continuously (J=1, K=1 toggles output)
• Note that the red and green LEDs appear dim when J=K=1
since they are toggling between on and off
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.
Details of the J-K Latch Block Diagram and Logic Chart on Next Page.
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