Functional Description
Truth Table
The ’AC/’ACT158 quad 2-input multiplexer selects four bits
of data from two sources under the control of a common Se-
lect input (S) and presents the data in inverted form at the
four outputs. The Enable input (E) is active-LOW. When E is
HIGH, all of the outputs (Z) are forced HIGH regardless of all
other inputs. The ’AC/’ACT158 is the logic implementation of
a 4-pole, 2-position switch where the position of the switch is
determined by the logic levels supplied to the Select input.
Inputs
Outputs
E
H
L
L
L
L
S
X
L
I0
X
L
I1
X
X
X
L
Z
H
H
L
L
H
X
X
H
H
H
L
H
A common use of the ’AC/’ACT158 is the moving of data
from two groups of registers to four common output busses.
The particular register from which the data comes is deter-
mined by the state of the Select input. A less obvious use is
as a function generator. The ’AC/’ACT158 can generate four
functions of two variables with one variable common. This is
useful for implementing gating functions.
=
=
=
H
L
X
HIGH Voltage Level
LOW Voltage Level
Immaterial
Logic Diagram
DS100273-5
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
www.national.com
2
NSC [ National Semiconductor ]
