Full Adder Chip

1. Full Adder Chip

Full Adder chip is used to add 3-bits.

2. Truth Table

|  a  |  b  | sum | carry |
|-----|-----|-----|-------|
|  0  |  0  |  0  |   0   |
|  0  |  1  |  1  |   0   |
|  1  |  0  |  1  |   0   |
|  1  |  1  |  0  |   1   |

3. Implementation (Logisim)

Representation of the Full Adder Chip in the logisim software using the previous gates.

4. Implementation (HDL)

The function in the above abstraction can help in the implementation of Full Adder Chip. You can use the Half Adder Chip you’ve built earlier.

sum = a XOR b XOR c

carry = (a AND b) OR (b AND c) OR (c AND a)

(Representation of the Full Adder Chip in HDL using previous gates.)

CHIP FullAdder {
    IN a, b, c;  // 1-bit inputs
    OUT sum,     // Right bit of a + b + c
        carry;   // Left bit of a + b + c

    PARTS:
    HalfAdder(a=a, b=b, sum=sumab, carry=carryab);
    HalfAdder(a=sumab, b=c, sum=sum, carry=temp);
    Or(a=temp, b=carryab, out=carry);
}