4-bit ALU X35448

Design a small ALU that receives two input numbers, a and b, and produces the result of an operation encoded by the signals op. There are four operations: addition ($a+b$, when op=00), subtraction ($a-b$, when op=01), transfer a ($a$, when op=10) and double a ($2a$, when op=11). The ALU also has an additional output (zero) that is activated when the result is zero.

Design the ALU for 4-bit operands.

Specification

module ALU(a, b, op, result, zero);
    input [3:0] a, b;
    input [1:0] op;
    output [3:0] result;
    output zero;

Input

• a and b are the two input 4-bit operands.

• op indicates the type of operation.

Output

• result is the 4-bit result of the operation.

• zero indicates when the result is zero.