n-bit adder/subtractor X89356

Design a circuit that performs the addition or subtraction of two $n$-bit numbers. The result (mod $2^n$) must be represented in $n$ bits also. The circuit has an input (op) that indicates which operation must be performed (0 for addition, 1 for subtraction).

The number of bits must be a parameter of the module, with a default value as shown in the specification.

Specification

module add_sub (a, b, op, result);
    parameter N=16;
    input [N-1:0] a, b;
    input op;
    output [N-1:0] result;

Input

• a and b are the two $n$-bit operands.

• op indicates the type of operation (0 for addition, 1 for subtraction).

Output

• result is the $n$-bit result of the operation (mod $2^n$).