74LCX157 Datasheet, PDF (2/9 Pages) Fairchild Semiconductor – Low Voltage Quad 2-Input Multiplexer with 5V Tolerant Inputs

Functional Description
The LCX157 is a quad 2-input multiplexer. It selects four
bits of data from two sources under the control of a com-
mon Select input (S). The Enable input (E) is active-LOW.
When E is HIGH, all of the outputs (Z) are forced LOW
regardless of all other inputs. The LCX157 is the logic
implementation of a 4-pole, 2-position switch where the
position of the switch is determined by the logic levels sup-
plied to the Select input. The logic equations for the outputs
are shown below:
Z_a = E • (I_1a • S + I_0a • S)
Z_b = E • (I_1b • S + I_0b • S)
Z_c = E • (I_1c • S + I_0c • S)
Z_d = E • (I_1d • S + I_0d • S)
A common use of the LCX157 is the moving of data from
two groups of registers to four common output busses. The
particular register from which the data comes is determined
by the state of the Select input. A less obvious use is as a
function generator. The LCX157 can generate any four of
the sixteen different functions of two variables with one
variable common. This is useful for implementing gating
functions.
Logic Diagram
Truth Table
Inputs
E
S
I₀
H
X
X
L
H
X
L
H
X
L
L
L
L
L
H
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Outputs
I₁
Z
X
L
L
L
H
H
X
L
X
H
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
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