© 2000 Fairchild Semiconductor Corporation

DS006107

www.fairchildsemi.com

September 1986

Revised March 2000

DM74AS257 • DM74AS258

3-STATE Quad 1 of 2 Line Data Selector/Multiplexers

General Description

These data selectors/multiplexers contain inverters and

drivers to supply full on-chip data selection to the four 3-

STATE outputs that can interface directly with data lines of

bus-organized systems. A 4-bit word selected from one of

two sources is routed to the four outputs. The DM74AS257

presents true data whereas the DM74AS258 presents

inverted data to minimize propagation delay time.

This 3-STATE output feature means that n-bit (paralleled)

data selectors with up to 300 sources can be implemented

for data buses. It also permits the use of standard TTL reg-

isters for data retention throughout the system.

Features

s Switching specifications at 50 pF

s Switching specifications guaranteed over full tempera-

s Advanced oxide-isolated, ion-implanted Schottky TTL

process

s Functionally and pin for pin compatible with Schottky,

low power Schottky, and advanced low power Schottky

TTL counterpart

s Improved AC performance over Schottky, low power

Schottky, and advanced low power Schottky counter-

parts

s 3-STATE buffer-type output drive bus lines directly

s Expand any data input point

s Multiplex dual data buses

s General four functions of two variables (one variable is

common)

s Source programmable counters

Ordering Code:

Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.

Connection Diagram

Function Table

H

= HIGH Level

L

= LOW Level

X

= Don't Care

Z

= High Impedance (OFF)

Order Number

Package Number

Package Description

DM74AS257M

M16A

16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow

DM74AS257N

N16E

16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

DM74AS258M

M16A

16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow

DM74AS258N

N16E

16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

INPUTS

OUTPUT Y

OUTPUT

SELECT

A

B

AS257

AS258

CONTROL

HX

X

X

Z

Z

LL

L

X

L

H

LL

H

X

H

L

LH

X

L

L

H

LH

X

H

H

L