SN54HCT138, SN74HCT138

3LINE TO 8LINE DECODERS/DEMULTIPLEXERS

SCLS171E − MARCH 1984 − REVISED SEPTEMBER 2003

2

POST OFFICE BOX 655303

description/ordering information (continued)

The conditions at the binary-select inputs and the three enable inputs select one of eight output lines. Two

active-low (G) and one active-high (G) enable inputs reduce the need for external gates or inverters when

expanding. A 24-line decoder can be implemented without external inverters, and a 32-line decoder requires

only one inverter. An enable input can be used as a data input for demultiplexing applications.

FUNCTION TABLE

INPUTS

OUTPUTS

ENABLE

SELECT

OUTPUTS

G1

G2A

G2B

C

B

A

Y0

Y1

Y2

Y3

Y4

Y5

Y6

Y7

X

H

X

X

X

X

H

H

H

H

H

H

H

H

X

XH

X

XX

H

HH

HH

HH

H

L

XX

X

XX

H

HH

HH

HH

H

H

LL

L

LL

L

HH

HH

HH

H

H

LL

L

LH

H

L

H

HH

HH

H

H

LL

L

HLH

H

L

HH

HH

H

H

LL

L

HH

H

HH

L

H

HH

H

H

LL

H

LL

H

HH

H

L

HH

H

H

LL

H

LH

H

HH

HH

L

H

H

H

LL

H

HLH

HH

HH

H

L

H

H

L

L

H

H

H

H

H

H

H

H

H

H

L