MC74ACT258N 查看數據表（PDF） - Motorola => Freescale

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MC74ACT258N

Quad 2-Input Multiplexer with 3-State Outputs

Motorola => Freescale 

MC74AC258 MC74ACT258

FUNCTIONAL DESCRIPTION

The MC74AC258/74ACT258 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 I0x inputs are selected and when

Select is HIGH, the I1x 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:

Za = OE•(I1a•S+I0a•S)

Zb = OE•(I1b•S+I0b•S)

Zc = OE•(I1c•S+I0c•S)

Zd = OE•(I1d•S+I0d•S)

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 the

Output Enable signals to 3-state devices whose outputs are

tied together are designed so there is no overlap.

OE

I0a

LOGIC DIAGRAM

I1a

I0b

I1b

I0c

I1c

I0d

I1d

S

Za

Zb

Zc

Zd

Please note that this diagram is provided only for the understanding of logic

operations and should not be used to estimate propagation delays.

FACT DATA

5-2

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