DM74AS257 Selector/Multiplexers Datasheet

DM74AS257 Datasheet, PDF, Equivalent


Part Number

DM74AS257

Description

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

Manufacture

Fairchild Semiconductor

Total Page 6 Pages
Datasheet
Download DM74AS257 Datasheet


DM74AS257
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-
ture and VCC range
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:
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
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Connection Diagram
Function Table
INPUTS
OUTPUT
SELECT
CONTROL
A
H XX
L LL
L LH
L HX
LH
H = HIGH Level
L = LOW Level
X = Don't Care
Z = High Impedance (OFF)
X
OUTPUT Y
B AS257 AS258
XZ Z
XL H
XH
L
LLH
HH
L
© 2000 Fairchild Semiconductor Corporation DS006107
www.fairchildsemi.com

DM74AS257
Logic Diagrams
DM74AS257
DM74AS258
www.fairchildsemi.com
2


Features DM74AS257 • DM74AS258 3-STATE Quad 1 o f 2 Line Data Selector/Multiplexers Se ptember 1986 Revised March 2000 DM74AS 257 • DM74AS258 3-STATE Quad 1 of 2 L ine Data Selector/Multiplexers General Description These data selectors/multip lexers contain inverters and drivers to supply full on-chip data selection to the four 3STATE outputs that can interf ace directly with data lines of bus-org anized systems. A 4-bit word selected f rom one of two sources is routed to the four outputs. The DM74AS257 presents t rue data whereas the DM74AS258 presents inverted data to minimize propagation delay time. This 3-STATE output feature means that n-bit (paralleled) data sel ectors with up to 300 sources can be im plemented for data buses. It also permi ts the use of standard TTL registers fo r data retention throughout the system. Features s Switching specifications a t 50 pF s Switching specifications guar anteed over full temperature and VCC ra nge s Advanced oxide-isolated, ion-implanted Schottky TTL process s.
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