5-1
FACT DATA
The MC74AC257/74ACT257 is a quad 2-input multiplexer with 3-state outputs.
Four bits of data from two sources can be selected using a Common Data Select
input. The four outputs present the selected data in true (noninverted) form. The
outputs may be switched to a high impedance state by placing a logic HIGH on
the common Output Enable (OE) input, allowing the outputs to interface directly
with bus-oriented systems.
Multiplexer Expansion by Tying Outputs Together
Noninverting 3-State Outputs
Outputs Source/Sink 24 mA
′
ACT257 Has TTL Compatible Inputs
15
16
14
13
12
11
10
2
1
S
3
4
5
6
7
VCC
9
8
OE
I0c
I1c
Zc
I0d
I1d
Zd
I0a
I1a
Za
I0b
I1b
Zb
GND
PIN NAMES
S
OE
I0a–I0d
I1a–I1d
Za–Zd
Common Data Select Input
3-State Output Enable Input
Data Inputs from Source 0
Data Inputs from Source 1
3-State Multiplexer Outputs
TRUTH TABLE
Output
Enable
Select
Input
Data
Inputs
Outputs
OE
S
I0
X
X
X
L
H
I1
X
L
H
X
X
Z
H
L
L
L
L
X
H
H
L
L
Z
L
H
L
H
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Z = High Impedance
QUAD 2-INPUT
MULTIPLEXER WITH
3-STATE OUTPUTS
N SUFFIX
CASE 648-08
PLASTIC
D SUFFIX
CASE 751B-05
PLASTIC
LOGIC SYMBOL
S
OE I0aI1aI0bI1b
Zb
I0cI1cI0dI1d
Za
Zc
Zd