MC74ACT257 ON Semiconductor, MC74ACT257 Datasheet - Page 2

• Manufacturer Part Number: MC74ACT257
• Description: QUAD 2-INPUT MULTIPLEXER WITH 3-STATE OUTPUTS
• Manufacturer: ON Semiconductor

multiplexer with 3–state outputs. It selects four bits of data
from two sources under control of a Common Data Select
input. When the Select input is LOW, the I
selected and when Select is HIGH, the I
selected. The data on the selected inputs appears at the
outputs in true (noninverted) form. The device is the logic
The MC74AC257/74ACT257 is a quad 2–input
FUNCTIONAL DESCRIPTION
Figure 2. Logic Symbol
NOTE:
This diagram is provided only for the understanding of logic operations
and should not be used to estimate propagation delays.
MC74AC257, MC74ACT257
1x
0x
inputs are
inputs are
Figure 3. Logic Diagram
http://onsemi.com
2
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:
are forced to a high impedance state. If the outputs are tied
together, all but one device must be in the high impedance
state to avoid high currents that would exceed the maximum
ratings. Designers should ensure the Output Enable signals
to 3–state devices whose outputs are tied together are
designed so there is no overlap.
Z
Z
Z
Z
When the Output Enable input (OE) is HIGH, the outputs
a
b
c
d
= OE (I
= OE (I
= OE (I
= OE (I
1a
1c
1b
1d
S+I
S+I
S+I
S+I
0a
0c
0b
0d
S)
S)
S)
S)