Elenco Understanding Logic Gates and Circuits - Manual (Page 18)

U19 U16
Project 11: Gated S-R Latch
The Enable input (E) can be used as a clock input, or a read/write strobe.
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U19 U16
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2 This circuit demonstrates how a Gated S-R Latch
works. Turn the slide switch (S1) on. Connect one
the loose end of the orange wire to 1 (Latch
enabled). Repeat the experiments from Project 9
to verify that this now functions as an S-R NOR
Latch. Now with S=1 and R=0 (red LED should be
on), disconnect the orange wire from 1 and
connect it to 0 (Latch disabled).
The red LED
should now remain on no matter whether you
connect the red and black wires to 1 or 0. Now
with S=0 and R= 1, move the orange wire back to 1
(Latch enabled so red LED should go off). Now
move the orange wire back to 0 again (Latch
disabled). The red LED should now remain off no
matter whether you connect the red and black
wires 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.
Input (E) Q, Q
0 Hold State
1 Same as S-R Latch
R Q
S
Q
E
Operates as S-R
Latch when E=1
Holds output
state when E=0
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Q