JK FLIP FLOPS

JK Flip-Flop
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Like the 7474, the 74109 has two flip-flops on the same chip. The difference is that
the 74109 has two JK flip-flops. Use only one of these flip-flops in this part of the
experiment.
A. Asynchronous Preset and Clear
1. Connect power and ground to the 74109. Notice that these connections are
different from other chips. Connect Q and Q' to data indicators. Connect
DS-1 and DS-2 to the preset and clear inputs. Perform the same operations
with the preset and clear inputs of the JK flip-flop as was done with the D
flip- flop.
B. Normal operation using the J, K, and Clock Inputs
1. The JK flip-flop is a positive edge-triggered device which means that the
outputs, Q and Q' will only be affected by the J and K inputs when a low to
high transition is produced at the clock input. Note that for the 74019 the J
input is high true, the K input is low true (note the bar over the K input in
the 74109 data sheet). Use a 7404 inverter to invert the switch input to the
EE 3714 Flip-Flops
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K input so that both J and K are high true inputs. You may have a 7476 in
your parts kit instead of a 74019 - a 7476 also has two JK flip-flops, but
both J and K are high true inputs so you would not need the inverter with a
7476.
2. The JK flip-flop operation is as follows (assuming that both J,K are high
true - 0 = L, 1 = H):
a. J=0, K=0 : No Change. Q will not change state (neither will Q') when a
negative edge is supplied to the clock.
b. J=0, K=1 : Go to 0. Q will become a 0 (Q' goes to 1) when a negative
edge is supplied to the clock.
c. J=1, K=0 : Go to 1. Q will become a 1 (Q' goes to 0) when a negative
edge is supplied to the clock.
d. J=1, K=1 : Complement. Q gets the complement of its previous state
(as does Q') when a negative edge is supplied to the clock.
C. JK Flip-Flop Truth Table
1. Consult the TTL Data Book for one version of the JK flip-flop truth table.
2. Construct a truth table similar to the one which was made for the D flip-flop
(fill out Table II on lab data sheet). Include columns for J, K, the clock, Q,
preset, clear, and Q+.