Functional Description

The ’AC/’ACT157 is a quad 2-input multiplexer. It selects

four bits of data from two sources under the control of a com-

mon Select input (S). The Enable input (E) is active-LOW.

When E is HIGH, all of the outputs (Z) are forced LOW re-

gardless of all other inputs. The ’AC/’ACT157 is the logic

implementation of a 4-pole, 2-position switch where the posi-

tion of the switch is determined by the logic levels supplied to

the Select input. The logic equations for the outputs are

shown below:

Z

Z

Z

Z

A common use of the ’AC/ACT157 is the moving of data from

two groups of registers to four common output busses. The

particular register from which the data comes is determined

by the state of the Select input. A less obvious use is as a

function generator. The ’AC/’ACT157 can generate any four

of the sixteen different functions of two variables with one

variable common. This is useful for implementing gating

functions.

Truth Table

Inputs

Outputs

E

SI

0

I

1

Z

HX

X

X

L

LH

X

L

L

LH

X

H

H

LL

L

X

L

LL

H

X

H

H = HIGH Voltage Level

L = LOW Voltage Level

X = Immaterial

Logic Diagram

DS100272-5

Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.

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