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.