Functional Description
The ’AC/’ACT157 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 re-
gardless of all other inputs. The ’AC/’ACT157 is the logic
implementation of a 4-pole, 2-position switch where the posi-
tion of the switch is determined by the logic levels supplied to
the Select input. The logic equations for the outputs are
shown below:
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 ’AC/ACT157 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 ’AC/’ACT157 can generate any four
Logic Diagram
of the sixteen different functions of two variables with one
variable common. This is useful for implementing gating
functions.
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
DS100272-5
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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