7485
器件资料摘要：
TL/F/6379
54LS85/DM54LS85/DM74LS85
4-Bit
Magnitude
Comparators
June 1989
54LS85/DM54LS85/DM74LS85
4-Bit Magnitude Comparators
General Description
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
greater length may be compared by connecting compara-
tors in cascade. The A
l
B, A
k
B, and A e B outputs of a
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
have a high-level voltage applied to the A e B input. The
cascading path is implemented with only a two-gate-level
delay to reduce overall comparison times for long words.
Features
Y
Typical power dissipation 52 mW
Y
Typical delay (4-bit words) 24 ns
Y
Alternate Military/Aerospace device (54LS85) is avail-
able. Contact a National Semiconductor Sales Office/
Distributor for specifications.
Connection Diagram
Dual-In-Line Package
TL/F/6379–1
Order Number 54LS85DMQB,
54LS85FMQB, 54LS85LMQB,
DM54LS85J, DM54LS85W,
DM74LS85M or DM74LS85N
See NS Package Number E20A,
J16A, M16A, N16E or W16A
Function Table
Comparing Cascading
Outputs
Inputs Inputs
A3, B3 A2, B2 A1, B1 A0, B0 A
l
BA
k
BAeBA
l
BA
k
BAeB
A3
l
B3 X X X X X X H L L
A3
k
B3 X X X X X X L H L
A3 e B3 A2
l
B2 X X X X X H L L
A3 e B3 A2
k
B2 X X X X X L H L
A3 e B3 A2 e B2 A1
l
B1 X X X X H L L
A3 e B3 A2 e B2 A1
k
B1 X X X X L H L
A3 e B3 A2 e B2 A1 e B1 A0
l
B0 X X X H L L
A3 e B3 A2 e B2 A1 e B1 A0
k
B0 X X X L H L
A3 e B3 A2 e B2 A1 e B1 A0 e B0 H L L H L L
A3 e B3 A2 e B2 A1 e B1 A0 e B0 L H L L H L
A3 e B3 A2 e B2 A1 e B1 A0 e B0 LHLLH
A3 e B3 A2 e B2 A1 e B1 A0 e XXHL
A3 e B3 A2 e B2 A1 e B1 A0 e B0HHLLLL
A3 e B3 A2 e B2 A1 e B1 A0 e LLLHHL
HeHigh Level, L e Low Level, X e Don’t Care
C
1995 National Semiconductor Corporation RRD-B30M105/Printed in U. S. A.
54LS85/DM54LS85/DM74LS85
4-Bit
Magnitude
Comparators
June 1989
54LS85/DM54LS85/DM74LS85
4-Bit Magnitude Comparators
General Description
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
greater length may be compared by connecting compara-
tors in cascade. The A
l
B, A
k
B, and A e B outputs of a
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
have a high-level voltage applied to the A e B input. The
cascading path is implemented with only a two-gate-level
delay to reduce overall comparison times for long words.
Features
Y
Typical power dissipation 52 mW
Y
Typical delay (4-bit words) 24 ns
Y
Alternate Military/Aerospace device (54LS85) is avail-
able. Contact a National Semiconductor Sales Office/
Distributor for specifications.
Connection Diagram
Dual-In-Line Package
TL/F/6379–1
Order Number 54LS85DMQB,
54LS85FMQB, 54LS85LMQB,
DM54LS85J, DM54LS85W,
DM74LS85M or DM74LS85N
See NS Package Number E20A,
J16A, M16A, N16E or W16A
Function Table
Comparing Cascading
Outputs
Inputs Inputs
A3, B3 A2, B2 A1, B1 A0, B0 A
l
BA
k
BAeBA
l
BA
k
BAeB
A3
l
B3 X X X X X X H L L
A3
k
B3 X X X X X X L H L
A3 e B3 A2
l
B2 X X X X X H L L
A3 e B3 A2
k
B2 X X X X X L H L
A3 e B3 A2 e B2 A1
l
B1 X X X X H L L
A3 e B3 A2 e B2 A1
k
B1 X X X X L H L
A3 e B3 A2 e B2 A1 e B1 A0
l
B0 X X X H L L
A3 e B3 A2 e B2 A1 e B1 A0
k
B0 X X X L H L
A3 e B3 A2 e B2 A1 e B1 A0 e B0 H L L H L L
A3 e B3 A2 e B2 A1 e B1 A0 e B0 L H L L H L
A3 e B3 A2 e B2 A1 e B1 A0 e B0 LHLLH
A3 e B3 A2 e B2 A1 e B1 A0 e XXHL
A3 e B3 A2 e B2 A1 e B1 A0 e B0HHLLLL
A3 e B3 A2 e B2 A1 e B1 A0 e LLLHHL
HeHigh Level, L e Low Level, X e Don’t Care
C
1995 National Semiconductor Corporation RRD-B30M105/Printed in U. S. A.