SN74LS157

http://onsemi.com

3

LOGIC DIAGRAM

14

1

26

7

3

4

5

9

11

12

10

13

15

GND = PIN 8

= PIN NUMBERS

FUNCTIONAL DESCRIPTION

The LS157 is a Quad 2-Input Multiplexer fabricated with

the Schottky barrier diode process for high speed. It selects

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

common Select Input (S). The Enable Input (E) is active

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

LOW regardless of all other inputs.

The LS157 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:

A common use of the LS157 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 LS157 can generate any four of the

16 different functions of two variables with one variable

common. This is useful for implementing highly irregular

logic.

TRUTH TABLE

ENABLE

SELECT

INPUT

INPUTS

OUTPUT

E

S

Z

H

X

X

X

L

L

H

X

LL

L

H

X

HH

L

L

L

XL

L

L

H

X

H

H = HIGH Voltage Level

L = LOW Voltage Level

X = Don’t Care