✏️ Explanatory Question

[Computer Hardware]

Question:

Write the canonical Product-of-Sum (POS) expression for the Sum and Carry of a Full Adder.

👁 3 Views
📘 Detailed Answer
🟢 Easy
💡

Answer with Explanation

Answer:

Sum (S):

S(A,B,C) = ΠM(0,3,5,6)

Carry (C):

C(A,B,C) = ΠM(0,1,2,4)

Explanation:

A Full Adder has three inputs:

A, B, C (Carry input)

and two outputs:

  • Sum (S)
  • Carry (C)

Truth Table of Full Adder:

A B C | S CARRY

0 0 0 | 0   0
0 0 1 | 1   0
0 1 0 | 1   0
0 1 1 | 0   1
1 0 0 | 1   0
1 0 1 | 0   1
1 1 0 | 0   1
1 1 1 | 1   1

Canonical POS Form:

In Product-of-Sums (POS), we take the rows where output is 0.

For Sum (S):

Output S = 0 for rows:

0, 3, 5, 6

Therefore:

S(A,B,C) = ΠM(0,3,5,6)

For Carry (C):

Output Carry = 0 for rows:

0,1,2,4

Therefore:

C(A,B,C) = ΠM(0,1,2,4)

Conclusion:

  • Canonical POS uses maxterms where output = 0
  • Sum:
    ΠM(0,3,5,6)
  • Carry:
    ΠM(0,1,2,4)