Binary Addition
Binary Addition (1)
Binary Addition (2)
Derivation of ∑ Question: What primitive best implements ∑? Inputs: A, B Outputs: xor (∑, A, B) BA∑
Derivation of Carry Out Question: What primitive best implements C o ? Inputs: A, B Outputs: and (C o, A, B) BACoCo
A Half Adder A half adder is useful for adding LSB.
Limitation of a Half Adder A half-adder does not account for carry-in.
Truth Table of ∑ of a Full Adder C in BA∑ Identical to ∑ of a Half Adder C in +B+A=C in +∑ HA =C in XOR ∑ HA
Truth Table of C o of a Full Adder C in BACoCo Identical to ∑ of a Half Adder Use a Half Adder with C in and ∑ HA to generate C o
Schematic of a Full Adder
A 3 bit parallel adder