Unit LoadingFan Out

54F74F

Pin Names

Description

UL

HIGHLOW

Source 0 Data Inputs

1010

Source 1 Data Inputs

1010

E

Enable Input (Active LOW)

1010

S

Select Input

1010

Outputs

50333

b

1 mA20 mA

Functional Description

The ’F157A is a quad 2-input multiplexer 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 ’F157A 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 in-

put The logic equations for the outputs are shown below

A common use of the ’F157A is the moving of data from two

groups of registers to four common output busses The par-

ticular 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 ’F157A 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

Inputs

Output

E

Z

HX

X

X

L

LH

X

L

L

LH

X

H

H

LL

L

X

L

LL

H

X

H

Logic Diagram

TLF9483 – 4

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

2