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
Logic Diagram
Functional Description
Outputs
The LVQ157 is a quad 2-input multiplexer. It selects four
bits of data from two sources under the control of a com-
I1
Z
mon Select input (S). The Enable input (E) is active-LOW.
X
L
When E is HIGH, all of the outputs (Z) are forced LOW
regardless of all other inputs. The LVQ157 is the logic
L
L
implementation of a 4-pole, 2-position switch where the
H
H
position of the switch is determined by the logic levels sup-
X
L
plied to the Select input. The logic equations for the outputs
are shown below:
X
H
Za = E • (I1a • S + I0a • S)
Zb = E • (I1b • S + I0b • S)
Zc = E • (I1c • S + I0c • S)
Zd = E • (I1d • S + I0d • S)
A common use of the LVQ157 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 LVQ157 can generate any four of
the sixteen different functions of two variables with one
variable common. This is useful for implementing gating
functions.
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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