DM54LS251 Datasheet, PDF (1/6 Pages) National Semiconductor (TI) – TRI-STATE Data Selectors/Multiplexers

June 1989
DM54LS251 DM74LS251
TRI-STATE Data Selectors Multiplexers
General Description
These data selectors multiplexers contain full on-chip bina-
ry decoding to select one-of-eight data sources and feature
a strobe-controlled TRI-STATE output The strobe must be
at a low logic level to enable these devices The TRI-STATE
outputs permit direct connection to a common bus When
the strobe input is high both outputs are in a high-imped-
ance state in which both the upper and lower transistors of
each totem-pole output are off and the output neither drives
nor loads the bus significantly When the strobe is low the
outputs are activated and operate as standard TTL totem-
pole outputs
To minimize the possibility that two outputs will attempt to
take a common bus to opposite logic levels the output con-
trol circuitry is designed so that the average output disable
time is shorter than the average output enable time
Features
Y _{TRI-STATE version of LS151}
Y _{Interface directly with system bus}
Y _{Perform parallel-to-serial conversion}
Y _{Permit multiplexing from N-lines to one line}
Y _{Complementary outputs provide true and inverted data}
Y _{Maximum number of common outputs}
54LS 49
74LS 129
Y _{Typical propagation delay time (D to Y)}
54LS 17 ns
74LS 17 ns
Y _{Typical power dissipation}
54LS 35 mW
74LS 35 mW
Connection Diagram
Dual-In-Line Package
Function Table
Inputs
Outputs
Select
Strobe
Y
W
C
B
A
S
X
X
X
H
Z
Z
L
L
L
L
D0
D0
L
L
H
L
D1
D1
L
H
L
L
D2
D2
L
H
H
L
D3
D3
H
L
L
L
D4
D4
H
L
H
L
D5
D5
H
H
L
L
D6
D6
H
H
H
L
D7
D7
H e High Logic Level L e Low Logic Level
X e Don’t Care Z e High Impedance (Off)
D0 D1 D7 e The level of the respective D input
TL F 6415 – 1
Order Number DM54LS251J DM54LS251W
DM74LS251M or DM74LS251N
See NS Package Number J16A M16A N16E or W16A
TRI-STATE is a registered trademark of National Semiconductor Corporation
C1995 National Semiconductor Corporation TL F 6415
RRD-B30M105 Printed in U S A