May 1992
DM54LS259/DM74LS259 8-Bit Addressable Latches
General Description
Features
Y
8-Bit parallel-out storage register performs serial-to-par-
allel conversion with storage
Asynchronous parallel clear
Active high decoder
These 8-bit addressable latches are designed for general
purpose storage applications in digital systems. Specific
uses include working registers, serial-holding registers, and
active-high decoders or demultiplexers. They are multifunc-
tional devices capable of storing single-line data in eight
addressable latches, and being a 1-of-8 decoder or demulti-
plexer with active-high outputs.
Y
Y
Y
Y
Y
Y
Y
Enable/disable input simplifies expansion
Direct replacement for Fairchild 9334
Expandable for N-bit applications
Four distinct functional modes
Typical propagation delay times:
Enable-to-output 18 ns
Four distinct modes of operation are selectable by control-
ling the clear and enable inputs as enumerated in the func-
tion table. In the addressable-latch mode, data at the data-
in terminal is written into the addressed latch. The ad-
dressed latch will follow the data input with all unaddressed
latches remaining in their previous states. In the memory
mode, all latches remain in their previous states and are
unaffected by the data or address inputs. To eliminate the
possibility of entering erroneous data in the latches, the en-
able should be held high (inactive) while the address lines
are changing. In the 1-of-8 decoding or demultiplexing
mode, the addressed output will follow the level of the D
input with all other outputs low. In the clear mode, all out-
puts are low and unaffected by the address and data inputs.
Data-to-output 16 ns
Address-to-output 21 ns
Clear-to-output 17 ns
Y
Fan-out
I
(sink current)
OL
54LS259 4 mA
74LS259 8 mA
(source current) 0.4 mA
b
I
OH
Y
Typical I
22 mA
CC
Connection Diagram
Function Table
Inputs
Output of Each
Addressed Other
Dual-In-Line Package
Function
Latch
Output
Clear
E
H
H
L
L
H
L
D
Q
Q
L
Addressable Latch
Memory
8-Line Demultiplexer
Clear
i0
Q
i0
i0
D
L
L
H
L
Latch Selection Table
Select Inputs
B
Latch
Addressed
C
A
L
L
L
L
L
H
H
L
L
H
L
H
L
0
1
2
3
4
5
6
7
L
H
H
H
H
L
H
H
H
L
H
TL/F/6418–1
Order Number DM54LS259E, DM54LS259J,
DM54LS259W, DM74LS259M,
DM74LS259WM or DM74LS259N
See NS Package Number E20A, J16A,
M16A, M16B, N16E or W16A
e
e
e
Low Level
H
D
Q
High Level, L
the Level of the Data Input
e
e
0, 1, . . . 7, as Appropriate) before the Indicated
the Level of Q (i
i
i0
Steady-State Input Conditions Were Established.
C
1995 National Semiconductor Corporation
TL/F/6418
RRD-B30M105/Printed in U. S. A.