74act157mtcx-nl Fairchild Semiconductor, 74act157mtcx-nl Datasheet - Page 2

• Manufacturer Part Number: 74act157mtcx-nl
• Description: 74ac157 * 74act157 Quad 2-input Multiplexer
• Manufacturer: Fairchild Semiconductor

www.fairchildsemi.com
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
common 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 AC/ACT157 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. The logic equations for the
outputs are shown below:
A common use of the AC/ACT157 is the moving of data
from two groups of registers to four common output bus-
ses. 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 gener-
ate any four of the sixteen different functions of two vari-
ables with one variable common. This is useful for
implementing gating functions.
Logic Diagram
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
Z
Z
Z
Z
a
b
d
c
E • (I
E • (I
E • (I
E • (I
1a
1b
1c
1d
• S
• S
• S
• S
I
I
I
I
0c
0d
0a
0b
• S)
• S)
• S)
• S)
2
Truth Table
H
L
X
LOW Voltage Level
HIGH Voltage Level
Immaterial
E
H
L
L
L
L
S
X
H
H
L
L
Inputs
I
X
X
X
H
L
0
I
X
H
X
X
L
1
Outputs
H
H
Z
L
L
L