MC74AC258 Motorola, MC74AC258 Datasheet - Page 2

• Manufacturer Part Number: MC74AC258
• Description: QUAD 2-INPUT MULTIPLEXER WITH 3-STATE OUTPUTS
• Manufacturer: Motorola

FUNCTIONAL DESCRIPTION
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 0x inputs are selected and when
Select is HIGH, the I 1x inputs are selected. The data on the
selected inputs appears at the outputs in inverted form. The
MC74AC258/74ACT258 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:
Z a = OE (I 1a S+I 0a S)
Z b = OE (I 1b S+I 0b S)
Z c = OE (I 1c S+I 0c S)
Z d = OE (I 1d S+I 0d S)
The MC74AC258/74ACT258 is a quad 2-input multiplexer
OE
I 0a
Please note that this diagram is provided only for the understanding of logic
operations and should not be used to estimate propagation delays.
Z a
MC74AC258 MC74ACT258
I 1a
I 0b
LOGIC DIAGRAM
Z b
FACT DATA
I 1b
5-2
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 the
Output Enable signals to 3-state devices whose outputs are
tied together are designed so there is no overlap.
I 0c
When the Output Enable input (OE) is HIGH, the outputs
Z c
I 1c
I 0d
Z d
I 1d
S