Logical Unit
A designer bungled this pass-gate implementation of a generic logic gate (4 to 1 mux).
F1
F3
F0
F2
Out
YX
Remember that pass-gates are ideal switches that close when the control signal is high, and open when
the control signal is low. We'll ignore the complemented control signal here.
Part A
Determine which input is passed to the output under the following control conditions. Complete
the left-hand table below.
Part B
Using this pass-gate tree, what are the function inputs (
F
0
;F
1
;F
2
;F
3
) for the logical functions
listed in the right-hand table below?
Y X Out function
F
3
F
2
F
1
F
0
0 0 AND
0 1 XOR
1 0
X
1 1
X
+
Y