Fairchild Semiconductor DM74AS257SJX, DM74AS257N, DM74AS257MX, DM74AS257M Datasheet

© 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

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 3­STATE outputs that can interface d ire ctly with data li nes of
bus-organized systems. A 4-b it 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-bi t (paralleled)
data selectors with up to 300 sou rces can be impl ement ed
for data buses. It also permits the use of standard TTL reg­isters for data retention throughout the system.

Features

■ Switching specifications at 50 pF

■ Switching specifications guaranteed over full tempera-

ture and V

CC

range

■ Advanced oxide-isolated, ion-implanted Schottky TTL
process

■ Functionally and pin for pin compatible with Schottky,
low power Schottky, and advanced low power Schottky
TTL counterpart

■ Improved AC performance over Schottky, low power
Schottky, and advanced low power Schottky counter­parts

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

■ Expand any data input point

■ Multiplex dual data buses

■ General four functions of two variables (one variable is

common)

■ Source programmable counters

Ordering Code:

Devices also availab le in Tape and Reel. Specify by appending th e s uffix let t er “X” to the ordering code.

Connection Diagram Function Table

H = HIGH Level
L = LOW Level
X = Don't Care
Z = High Impedance (OF F )

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

HXXXZZ
LLLXLH
LLHXHL
LHXLLH
LHXHHL

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DM74AS257 • DM74AS258

Logic Diagrams

DM74AS257 DM74AS258