June 1989
54LS85/DM54LS85/DM74LS85
4-Bit Magnitude Comparators
General Description
e
These 4-bit magnitude comparators perform comparison of
straight binary or BCD codes. Three fully-decoded decisions
about two, 4-bit words (A, B) are made and are externally
available at three outputs. These devices are fully expand-
able to any number of bits without external gates. Words of
have a high-level voltage applied to the A
B input. The
cascading path is implemented with only a two-gate-level
delay to reduce overall comparison times for long words.
Features
Y
greater length may be compared by connecting compara-
k
Typical power dissipation 52 mW
l
e
tors in cascade. The A B, A B, and A
B outputs of a
Y
Typical delay (4-bit words) 24 ns
stage handling less-significant bits are connected to the cor-
responding inputs of the next stage handling more-signifi-
cant bits. The stage handling the least-significant bits must
Y
Alternate Military/Aerospace device (54LS85) is avail-
able. Contact a National Semiconductor Sales Office/
Distributor for specifications.
Connection Diagram
Dual-In-Line Package
Order Number 54LS85DMQB,
54LS85FMQB, 54LS85LMQB,
DM54LS85J, DM54LS85W,
DM74LS85M or DM74LS85N
See NS Package Number E20A,
J16A, M16A, N16E or W16A
TL/F/6379–1
Function Table
Comparing
Inputs
Cascading
Outputs
Inputs
l
k
l
k
e
e
A3, B3
A2, B2
A1, B1
A0, B0
A
B
A
B
A
B
A
B
A
B
A
B
l
A3 B3
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
H
L
X
X
X
X
X
X
X
X
L
X
X
X
X
X
X
X
X
L
H
L
L
H
L
L
L
L
L
L
L
L
L
L
L
H
H
L
L
k
A3 B3
l
e
e
e
e
e
e
e
e
e
e
e
e
A3
A3
A3
A3
A3
A3
A3
A3
A3
A3
A3
A3
e
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
A2 B2
H
L
k
A2 B2
H
L
l
e
e
e
e
e
e
e
e
e
e
A2
A2
A2
A2
A2
A2
A2
A2
A2
A2
B2
B2
B2
B2
B2
B2
B2
B2
B2
B2
A1 B1
H
L
k
A1 B1
H
L
l
e
e
e
e
e
e
e
e
A1
A1
A1
A1
A1
A1
A1
A1
B1
B1
B1
B1
B1
B1
B1
B1
A0 B0
H
L
k
A0 B0
H
L
e
e
e
e
e
e
A0
A0
A0
A0
A0
A0
B0
B0
B0
B0
B0
B0
H
L
H
L
L
H
L
L
H
H
L
L
X
H
L
X
H
L
L
L
L
L
L
H
H
e
e
H
High Level, L
Low Level, X
Don’t Care
C
1995 National Semiconductor Corporation
TL/F/6379
RRD-B30M105/Printed in U. S. A.