Page 53 - Digital Electronics by harish
P. 53
Figure : Logic diagram
= + = A ⊕ B
CARRY = A B
Inputs Outputs
A B CARRY SUM
0 0 0 0
0 1 0 1
1 0 0 1
1 1 1 0
As per the laws of binary addition, we get,
When A= 0 and B = 0
0 + 0 ===> Carry = 0, Sum = 0
When A= 0 and B = 1
0 + 1 ===> Carry = 0, Sum = 1
When A= 1 and B = 0
1 + 0 ===> Carry = 0, Sum = 1
When A= 1 and B = 1
1 + 1 ===> Carry = 1, Sum = 0
The logic diagram, truth table and logic equations for SUM and CARRY are given in figure.
From the truth table (A, B and SUM), we find that an EX-OR can be used to produce the
SUM. From the truth table (A, B and CARRY), we find that an AND gate can be used to
produce the CARRY.
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