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National -54F283.pdf
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National -54F283.pdf
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TL/F/9513
54F/74F283 4-Bit Binary Full Adder with Fast Carry
November 1994
54F/74F283
4-Bit Binary Full Adder with Fast Carry
General Description
The ’F283 high-speed 4-bit binary full adder with internal
carry lookahead accepts two 4-bit binary words (A
0
–A
3
,
B
0
–B
3
) and a Carry input (C
0
). It generates the binary Sum
outputs (S
0
–S
3
) and the Carry output (C
4
) from the most
significant bit. The ’F283 will operate with either active
HIGH or active LOW operands (positive or negative logic).
Features
Y
Guaranteed 4000V minimum ESD protection
Commercial Military
Package
Package Description
Number
74F283PC N16E 16-Lead (0.300
×
Wide) Molded Dual-In-Line
54F283DM (Note 2) J16A 16-Lead Ceramic Dual-In-Line
74F283SC (Note 1) M16A 16-Lead (0.150
×
Wide) Molded Small Outline, JEDEC
74F283SJ (Note 1) M16D 16-Lead (0.300
×
Wide) Molded Small Outline, EIAJ
54F283FM (Note 2) W16A 16-Lead Cerpack
54F283LL (Note 2) E20A 20-Lead Ceramic Leadless Chip Carrier, Type C
Note 1: Devices also available in 13
×
reel. Use suffix
e
SCX and SJX.
Note 2: Military grade device with environmental and burn-in processing. Use suffix
e
DMQB, FMQB and LMQB.
Logic Symbols Connection Diagrams
TL/F/9513–1
IEEE/IEC
TL/F/9513–4
Pin Assignment
for DIP, SOIC and Flatpak
TL/F/9513–2
Pin Assignment
for LCC
TL/F/9513–3
TRI-STATE
É
is a registered trademark of National Semiconductor Corporation.
C
1995 National Semiconductor Corporation RRD-B30M105/Printed in U. S. A.
Unit Loading/Fan Out
54F/74F
Pin Names Description
U.L. Input I
IH
/I
IL
HIGH/LOW Output I
OH
/I
OL
A
0
–A
3
A Operand Inputs 1.0/2.0 20 mA/
b
1.2 mA
B
0
–B
3
B Operand Inputs 1.0/2.0 20 mA/
b
1.2 mA
C
0
Carry Input 1.0/1.0 20 mA/
b
0.6 mA
S
0
–S
3
Sum Outputs 50/33.3
b
1 mA/20 mA
C
4
Carry Output 50/33.3
b
1 mA/20 mA
Functional Description
The ’F283 adds two 4-bit binary words (A plus B) plus the
incoming Carry (C
0
). The binary sum appears on the Sum
(S
0
–S
3
) and outgoing carry (C
4
) outputs. The binary weight
of the various inputs and outputs is indicated by the sub-
script numbers, representing powers of two.
2
0
(A
0
a
B
0
a
C
0
)
a
2
1
(A
1
a
B
1
)
a
2
2
(A
2
a
B
2
)
a
2
3
(A
3
a
B
3
)
e
S
0
a
2S
1
a
4S
2
a
8S
3
a
16C
4
Where (
a
)
e
plus
Interchanging inputs of equal weight does not affect the op-
eration. Thus C
0
,A
0
,B
0
can be arbitrarily assigned to pins
5, 6 and 7 for DIPS, and 7, 8 and 9 for chip carrier packages.
Due to the symmetry of the binary add function, the ’F283
can be used either with all inputs and outputs active HIGH
(positive logic) or with all inputs and outputs active LOW
(negative logic). See
Figure 1
. Note that if C
0
is not used it
must be tied LOW for active HIGH logic or tied HIGH for
active LOW logic.
Due to pin limitations, the intermediate carries of the ’F283
are not brought out for use as inputs or outputs. However,
other means can be used to effectively insert a carry into, or
bring a carry out from, an intermediate stage.
Figure 2
shows how to make a 3-bit adder. Tying the operand inputs
of the fourth adder (A
3
,B
3
) LOW makes S
3
dependent only
on, and equal to, the carry from the third adder. Using some-
what the same principle,
Figure 3
shows a way of dividing
the ’F283 into a 2-bit and a 1-bit adder. The third stage
adder (A
2
,B
2
,S
2
) is used merely as a means of getting a
carry (C
10
) signal into the fourth stage (via A
2
and B
2
) and
bringing out the carry from the second stage on S
2
. Note
that as long as A
2
and B
2
are the same, whether HIGH or
LOW, they do not influence S
2
. Similarly, when A
2
and B
2
are the same the carry into the third stage does not influ-
ence the carry out of the third stage.
Figure 4
shows a meth-
od of implementing a 5-input encoder, where the inputs are
equally weighted. The outputs S
0
,S
1
and S
2
present a bina-
ry number equal to the number of inputs I
1
–I
5
that are true.
Figure 5
shows one method of implementing a 5-input ma-
jority gate. When three or more of the inputs I
1
–I
5
are true,
the output M
5
is true.
C
0
A
0
A
1
A
2
A
3
B
0
B
1
B
2
B
3
S
0
S
1
S
2
S
3
C
4
Logic Levels L LHLHHLLHHHLLH
Active HIGH 0 0101100111001
Active LOW 1 1010011000110
Active HIGH: 0
a
10
a
9
e
3
a
16 Active LOW: 1
a
5
a
6
e
12
a
0
FIGURE 1. Active HIGH versus Active LOW Interpretation
2
Functional Description (Continued)
TL/F/9513–5
FIGURE 2. 3-Bit Adder
TL/F/9513–6
FIGURE 3. 2-Bit and 1-Bit Adders
TL/F/9513–7
FIGURE 4. 5-Input Encoder
TL/F/9513–8
FIGURE 5. 5-Input Majority Gate
3
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