The VHDL Code for full-adder circuit adds three one-bit binary numbers (A B Cin) and outputs two one-bit binary numbers, a sum (S) and a carry (Cout). Truth Table describes the functionality of full adder. sum(S) output is High when odd number of inputs are High. Cout is High, when two or more inputs are High. VHDL Code for full adder can also be constructed with 2 half adder Port mapping in to full adder.