74ACT258MTC FAIRCHILD [Fairchild Semiconductor], 74ACT258MTC Datasheet - Page 2

• Manufacturer Part Number: 74ACT258MTC
• Description: Quad 2-Input Multiplexer with 3-STATE Outputs
• Manufacturer: FAIRCHILD [Fairchild Semiconductor]

www.fairchildsemi.com
Truth Table
H
L
X
Z
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.
LOW Voltage Level
High Impedance
HIGH Voltage Level
Immaterial
Output
Enable
OE
H
L
L
Select
Input
H
H
S
X
I
X
X
X
0
Inputs
Data
I
X
H
L
1
Outputs
H
Z
Z
L
2
Functional Description
The ACT258 is a quad 2-input multiplexer with 3-STATE
outputs. It selects four bits of data from two sources under
control of a common Select input (S). When the Select
input is LOW, the I
is HIGH, the I
selected inputs appears at the outputs in inverted form.
The ACT258 is the logic implementation of a 4-pole, 2-
position switch where the position of the switch is deter-
mined by the logic levels supplied to the Select input. The
logic equations for the outputs are shown below:
When the Output Enable input (OE) is HIGH, the outputs
are forced to a high impedance state. If the outputs of the
3-STATE devices 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 that Output Enable signals to 3-STATE devices
whose outputs are tied together are designed so there is
no overlap.
Z
Z
Z
Z
a
b
c
d
1x
OE • (I
OE • (I
OE • (I
OE • (I
inputs are selected. The data on the
0x
inputs are selected and when Select
1c
1a
1b
1d
• S
• S
• S
• S
I
I
I
I
0c
0a
0b
0d
• S)
• S)
• S)
• S)