74AC157 STMicroelectronics, 74AC157 Datasheet - Page 2

• Manufacturer Part Number: 74AC157
• Description: QUAD 2 CHANNEL MULTIPLEXER
• Manufacturer: STMicroelectronics

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Functional Description
The AC/ACT153 is a dual 4-input multiplexer. It can select
two bits of data from up to four sources under the control of
the common Select inputs (S
plexer circuits have individual active-LOW Enables (E
which can be used to strobe the outputs independently.
When the Enables (E
outputs Z
logic implementation of a 2-pole, 4-position switch, where
the position of the switch is determined by the logic levels
supplied to the Select inputs. The logic equations for the
outputs are shown below.
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.
a
, Z
Z
Z
b
a
b
) are forced LOW. The AC/ACT153 is the
I
I
E
E
2a
2b
b
a
• S
• S
• (I
• (I
a
1
0b
1
0a
, E
• S
• S
• S
• S
b
0
0
) are HIGH, the corresponding
1
1
• S
0
• S
I
I
, S
3a
3b
0
0
1
• S
• S
). The two 4-input multi-
I
I
1
1
1a
1b
• S
• S
• S
• S
0
0
1
)
)
1
• S
• S
0
0
a
, E
b
)
2
Truth Table
H
L
X
S
X
H
H
H
H
L
L
L
L
LOW Voltage Level
HIGH Voltage Level
Immaterial
0
Select
Inputs
S
H
H
H
H
X
L
L
L
L
1
E
H
L
L
L
L
L
L
L
L
I
X
H
X
X
X
X
X
X
L
Inputs (a or b)
0
I
X
X
X
H
L
X
X
X
X
1
I
X
X
X
X
X
H
X
X
L
2
I
X
X
X
X
X
X
X
H
L
3
Output
H
H
H
H
Z
L
L
L
L
L