SN54AS882A, SN74AS882A
32-BIT LOOK-AHEAD CARRY GENERATORS
SDAS235 D2661, DECEMBER 1982 REVISED NOVEMBER 1985
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
Copyright
1985, Texas Instruments Incorporated
1
Directly Compatible With 'AS181B,
'AS1181, 'AS881B, and 'AS1881 ALUs
Package Options Include Plastic Small
Outline Packages, Both Plastic and
Ceramic Chip Carriers, and Standard
Plastic and Ceramic 300-mil DIPs
Capable of Anticipating the Carry Across a
Group of Eight 4-Bit Binary Adders
Cascadable to Perform Look-Ahead Across
n-Bit Adders
Typical Carry Time, C
n
to Any C
n+i
, is Less
Than 6 ns
Dependable Texas Instruments Quality and
Reliability
description
The 'AS882A is a high-speed look-ahead carry
generator capable of anticipating the carry across
a group of eight 4-bit adders permitting the
designer to implement look-ahead for a 32-bit ALU
with a single package or, by cascading 'AS882As,
full look-ahead is possible across n-bit adders.
The SN54AS882A is characterized for operation
over the full military temperature range of 55
C
to 125
C. The SN74AS882A is characterized for
operation from 0
C to 70
C.
'AS882A LOGIC EQUATIONS
C
n+8
=
G1 + P1G0+P1P0C
n
C
n+16
=
G3 + P3G2 + P3P2G1 + P3P2P1G0
+ P3P2P1P0C
n
C
n+24
=
G5 + P5G4 + P5P4G3 + P5P4P3G2
+ P5P4P3P2G1 + P5P4P3P2P1G0
+ P5P4P3P2P1P0C
n
C
n+32
=
G7 + P7G6 + P7P6G5 + P7P6P5G4
+ P7P6P5P4G3 + P7P6P5P4P3G2
+ P7P6P5P4P3P2G1 + P7P6P5P4P3P2P1G0
+ P7P6P5P4P3P2P1P0C
n
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
C
n
G0
P0
G1
P1
C
n + 8
G2
P2
G3
P3
C
n 16
GND
V
CC
NC
C
n + 32
P7
G7
P6
G6
C
n + 24
P5
G5
P4
G4
SN54AS882A . . . JT PACKAGE
SN74AS882A . . . DW OR NT PACKAGE
(TOP VIEW)
3 2 1
13 14
5
6
7
8
9
10
11
P7
G7
P6
NC
G6
C
n + 24
P5
G1
P1
C
n + 8
NC
G2
P2
G3
4
15 16 17 18
GND
NC
G4
P4
G5
P0
G0
NC
SN54AS882A . . . FK PACKAGE
SN74AS882A . . . DW OR NT PACKAGE
(TOP VIEW)
28 27 26
25
24
23
22
21
20
19
12
P3
NC
n + 32
C
CC
V
C
n
n + 16
C
NC No internal connection
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
SN54AS882A, SN74AS882A
32-BIT LOOK-AHEAD CARRY GENERATORS
SDAS235 D2661, DECEMBER 1982 REVISED NOVEMBER 1985
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
2
logic symbol
6
Cn+8
Cn+16
11
Cn+24
17
Cn+32
22
CO1
CO3
CO5
CO7
C1
CP0
CG0
CP1
CG1
CP2
CG2
CP3
CG3
CP4
CG4
CP5
CG5
CP6
CG6
CP7
CG7
CPG
G7
P7
G6
P6
G5
P5
G4
P4
G3
P3
G2
P2
G1
P1
GO
P0
Cn
16
14
10
8
4
5
2
3
1
7
9
13
15
19
18
21
20
This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
Pin numbers shown are for DW, JT, and NT packages.
SN54AS882A, SN74AS882A
32-BIT LOOK-AHEAD CARRY GENERATORS
SDAS235 D2661, DECEMBER 1982 REVISED NOVEMBER 1985
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
3
FUNCTION TABLE
FOR Cn + 32 OUTPUT
INPUTS
OUTPUT
G7
G6
G5
G4
G3
G2
G1
G0
P7
P6
P5
P4
P3
P2
P1
P0
Cn
Cn + 32
L
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
H
X
L
X
X
X
X
X
X
L
X
X
X
X
X
X
X
X
H
X
X
L
X
X
X
X
X
L
L
X
X
X
X
X
X
X
H
X
X
X
L
X
X
X
X
L
L
L
X
X
X
X
X
X
H
X
X
X
X
L
X
X
X
L
L
L
L
X
X
X
X
X
H
X
X
X
X
X
L
X
X
L
L
L
L
L
X
X
X
X
H
X
X
X
X
X
X
L
X
L
L
L
L
L
L
X
X
X
H
X
X
X
X
X
X
X
L
L
L
L
L
L
L
L
X
X
H
X
X
X
X
X
X
X
X
L
L
L
L
L
L
L
L
H
H
All other combinations
L
FUNCTION TABLE
FOR Cn+24 OUTPUT
INPUTS
OUTPUT
G5
G4
G3
G2
G1
G0
P5
P4
P3
P2
P1
P0
Cn
Cn + 24
L
X
X
X
X
X
X
X
X
X
X
X
X
H
X
L
X
X
X
X
L
X
X
X
X
X
X
H
X
X
L
X
X
X
L
L
X
X
X
X
X
H
X
X
X
L
X
X
L
L
L
X
X
X
X
H
X
X
X
X
L
X
L
L
L
L
X
X
X
H
X
X
X
X
X
L
L
L
L
L
L
X
X
H
X
X
X
X
X
X
L
L
L
L
L
L
H
H
All other combinations
L
Function Tables
FOR Cn + 8 OUTPUT
FOR Cn + 16 OUTPUT
INPUTS
OUTPUT
X
X
X
L
L
P1 P0 Cn
X
X
X
X
L
X
X
X
X
H
H
H
H
H
H
L
P2
X
X
L
L
L
Cn + 16
P3
X
L
L
L
L
G0
X
X
X
L
X
G1
X
X
L
X
X
G2
X
L
X
X
X
G3
L
X
X
X
X
All other combinations
INPUTS
OUTPUT
H
H
H
L
Cn + 16
Cn
X
X
H
X
L
L
P1 P0
X
X
L
G0
X
L
X
G1
L
X
X
All other combinations
Any inputs not shown in a given table are irrelevant with respect to that output.
SN54AS882A, SN74AS882A
32-BIT LOOK-AHEAD CARRY GENERATORS
SDAS235 D2661, DECEMBER 1982 REVISED NOVEMBER 1985
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
4
logic diagram (positive logic)
22
Cn + 32
Cn + 24
17
11
Cn + 16
6
Cn + 8
P7
21
19
P6
16
P5
14
P4
10
P3
8
P2
5
P1
3
P0
20
G7
18
G6
15
G5
13
G4
9
G3
7
G2
4
G1
2
G0
1
Cn
Pin numbers shown are for DW, JT, and NT packages.
SN54AS882A, SN74AS882A
32-BIT LOOK-AHEAD CARRY GENERATORS
SDAS235 D2661, DECEMBER 1982 REVISED NOVEMBER 1985
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
5
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage, V
CC
7 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage
7 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating free-air temperature range:
SN54AS882A
55
C to 125
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SN74AS882A
0
C to 70
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range
65
C to 150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
recommended operating conditions
SN54AS882A
SN74AS882A
UNIT
MIN
NOM
MAX
MIN
NOM
MAX
UNIT
VCC
Supply voltage
4.5
5
5.5
4.5
5
5.5
V
VIH
High-level input voltage
2
2
V
VIL
Low-level input voltage
0.8
0.8
V
IOH
High-level output current
2
2
mA
IOL
Low-level output current
20
20
mA
TA
Operating free-air temperature
55
125
0
70
C
SN54AS882A, SN74AS882A
32-BIT LOOK-AHEAD CARRY GENERATORS
SDAS235 D2661, DECEMBER 1982 REVISED NOVEMBER 1985
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
6
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
TEST CONDITIONS
SN54AS882A
SN74AS882A
UNIT
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNIT
VIK
VCC = 4.5 V,
II = 18 mA
1.2
1.2
V
VOH
VCC = 4.5 V to 5.5 V,
IOH = 2 mA
VCC 2
VCC 2
V
VOL
VCC = 4.5 V,
IOL = 20 mA
0.3
0.5
0.3
0.5
V
Cn, P 0, P1
0.4
0.4
G0, G6
0.8
0.8
G1, G2, G4
1.2
1.2
II
G3, G5
VCC = 5.5 V,
VI = 7 V
1.5
1.5
mA
G7
0.9
0.9
P2, P3
0.3
0.3
P4, P5
0.2
0.2
P6, P7
0.1
0.1
Cn, P 0, P1
80
80
G0, G6
160
160
G1, G2, G4
240
240
IIH
G3, G5
VCC = 5.5 V,
VI = 2.7 V
300
300
A
G7
180
180
P2, P3
60
60
P4, P5
40
40
P6, P7
20
20
Cn, P 0, P1
2
2
G0, G6
4
4
G1, G2, G4
6
6
IIL
G3, G5
VCC = 5.5 V,
VI = 0.4 V
7.5
7.5
mA
G7
4.5
4.5
P2, P3
1.5
1.5
P4, P5
1
1
P6, P7
0.5
0.5
IO
VCC = 5.5 V,
VO = 2.25 V
30
130
30
30
mA
ICC
VCC = 5.5 V
44
70
44
70
mA
All typical values are at VCC = 5 V, TA = 25
C.
The output conditions have been chosen to produce a current that closely approximates one half of the true short-circuit output current, IOS.
SN54AS882A, SN74AS882A
32-BIT LOOK-AHEAD CARRY GENERATORS
SDAS235 D2661, DECEMBER 1982 REVISED NOVEMBER 1985
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
7
switching characteristics (see Note 1)
VCC = 4.5 V to 5.5 V,
CL = 50 pF
CL = 50 pF,
RL = 500
PARAMETER
FROM
TO
RL = 500
,
T
MIN t MAX
UNIT
PARAMETER
FROM
(INPUT)
TO
(OUTPUT)
TA = MIN to MAX
UNIT
(INPUT)
(OUTPUT)
SN54AS882A
SN74AS882A
MIN
MAX
MIN
MAX
tPLH
C
Any output
2
10
2
9
tPHL
Cn
Any output
3
15
3
14
tPLH
P or G
C + 8
2
8
2
7
tPHL
P or G
Cn + 8
2
8
2
7
tPLH
P or G
C + 16
2
8
2
7
ns
tPHL
P or G
Cn + 16
2
8
2
7
tPLH
P or G
C + 24
2
8
2
7
tPHL
P or G
Cn + 24
2
11
2
10
tPLH
P or G
Cn + 32
1.5
9
2
8
tPHL
P or G
Cn + 32
2
13
2
12
NOTE 1: Load circuits and voltage waveforms are shown in Section 1.
SN54AS882A, SN74AS882A
32-BIT LOOK-AHEAD CARRY GENERATORS
SDAS235 D2661, DECEMBER 1982 REVISED NOVEMBER 1985
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
8
TYPICAL APPLICATION DATA
The application given in Figure 1 illustrates how the 'AS882A can implement look-ahead carry for a 32-bit ALU
(in this case, the popular 'AS881A) with a single package. Typical carry times shown are derived using the
standard Advanced Schottky load circuit.
'AS881A
'AS881A
'AS881A
Cn+16
Cn + 8
'AS881A
6 ns
6 ns
A
B
Cn
Cn4
'AS881A
Cn4
Cn
Cn
B
A
B
A
F
F
F
'AS881A
Cn
F
A
B
6 ns
F
Cn4
Cn4
Cn4
P0
G0
G1
P1
G2
P2
P4 G4
P3
G3
F
F
B
A
B
A
B
A
B
A
F
G5
P5
G6
P6
G7
P7
Cn + 24
7 ns
MSB
LSB
Cn
'AS882A
Cn + 32
Cn
Cn
Cn
Cn
Cn4
Cn4
Cn4
'AS881A
'AS881A
6 ns
6 ns
6 ns
6 ns
6 ns
6 ns
Figure 1
Likewise, Figure 2 illustrates the same 32-bit ALU using two 'AS882s. This shows the worst-case delay from
LSB to MSB to be 19 ns as opposed to 25 ns in Figure 1.
Cn
6 ns
7 ns
F
F
A
4
4
B
4
A
4
B
4
A
LSB
B
4
Cn
L
P0 G0
H
G1
P1
G2
P2
Cn
Cn
Cn + 8
4
B
A
4
B
4
4
A
F
Cn
6 ns
4
A
B
4
F
F
'AS881A
'AS881A
'AS881A
'AS881A
'AS881A
'AS881A
'AS881A
'AS881A
Cn
Cn
Cn
Cn
F
F
F
A
B
4
A
4
B
Cn + 16
Cn + 24
Cn + 32
P3 G3
P4 G4
P6 G6
P7 G7
G5
P5
'AS882A
P0
G0
P1 G1
Cn + 16
P2
Cn
G2
P3
G3
P4 G4
'AS882A
P5 G5
G6
P6
Cn + 24
P7 G7
Cn + 32
MSB
6 ns
6 ns
6 ns
6 ns
6 ns
Figure 2
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accordance with TI's standard warranty. Testing and other quality control techniques are utilized to the extent
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Copyright
1998, Texas Instruments Incorporated
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