Datasheet
SDAS215A − APRIL 1982 − REVISED DECEMBER 1994
Copyright 1994, Texas Instruments Incorporated
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
POST OFFICE BOX 1443 • HOUSTON, TEXAS 77251−1443
• 3-State Version of the ′ALS151
• 3-State Outputs Interface Directly With
System Bus
• Perform Parallel-to-Serial Conversion
• Complementary Outputs Provide True and
Inverted Data
• Package Options Include Plastic
Small-Outline (D) Packages, Ceramic Chip
Carriers (FK), and Standard Plastic (N) and
Ceramic (J) 300-mil DIPs
description
These data selectors/multiplexers contain full
binary decoding to select one-of-eight data
sources and feature controlled complementary
3-state outputs.
The 3-state outputs can interface with and drive
data lines of bus-organized systems. With all but
one of the common outputs disabled (at the
high-impedance state), the low impedance of the
signal-enabled output drives the bus line to a high
or low logic level. Both outputs are controlled by
the output-enable (OE
) input. The outputs are
disabled when OE
is high.
The SN54ALS251 is characterized for operation
over the full military temperature range of −55°C
to 125°C. The SN74ALS251 is characterized for
operation from 0°C to 70°C.
FUNCTION TABLE
INPUTS
OUTPUTS
SELECT
OE
OUTPUTS
C B A
OE
Y W
X X X H Z Z
L LLLD0 D0
L LHLD1 D1
L HLLD2 D2
L HHLD3 D3
H LLLD4 D4
H LHLD5 D5
H HLLD6 D6
H H H L D7 D7
D0, D1, . . . D7 = the level of the respective D input
SN54ALS251 ...J PACKAGE
SN74ALS251 ...D OR N PACKAGE
(TOP VIEW)
3212019
910111213
4
5
6
7
8
18
17
16
15
14
D5
D6
NC
D7
A
D1
D0
NC
Y
W
SN54ALS251 . . . FK PACKAGE
(TOP VIEW)
D2
D3
NC
C
B
D4
OE
GND
NC
NC − No internal connection
V
CC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
D3
D2
D1
D0
Y
W
OE
GND
V
CC
D4
D5
D6
D7
A
B
C
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