4-bit adder X97441

4-bit adder

Design a circuit that performs the addition of two 4-bit numbers. The result (mod 16) must be represented in 4 bits also.

Specification

module adder4(a, b, sum);
    input [3:0] a, b;
    output [3:0] sum;

Hint You may want to use several instances of a 1-bit full adder.

Input

• a and b are the two 4-bit number.

Output

• sum is the 4-bit output representing \((a+b) \textrm {~mod~} 16\).