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Functional Description

The 74F283 adds two 4-bit binary words (A plus B) plus the

of the various inputs and outputs is indicated by the sub-

script numbers, representing powers of two.

= S

Where (

+) = plus

Interchanging inputs of equal weight does not affect the

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 74F283 can be used either with all inputs and outputs

active HIGH (positive logic) or with all inputs and outputs

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

74F283 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 oper-

dependent only on, and equal to, the carry from the third

adder. Using somewhat the same principle, Figure 3 shows

a way of dividing the 74F283 into a 2-bit and a 1-bit adder.

does not influence the carry out of the third stage. Figure 4

shows a method of implementing a 5-input encoder, where

ing a 5-input majority gate. When three or more of the

Active HIGH: 0

+ 10 + 9 = 3 + 16

Active LOW: 1

+ 5 + 6 = 12 + 0

FIGURE 1. Active HIGH versus Active LOW Interpretation

FIGURE 2. 3-Bit Adder

FIGURE 3. 2-Bit and 1-Bit Adders

FIGURE 4. 5-Input Encoder

FIGURE 5. 5-Input Majority Gate

Logic Levels

L

L

H

L

H

H

L

L

H

H

H

L

L

H

Active HIGH

00

101

100

111

001

Active LOW

1

1

010

011

000

110