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--! @file

--! @brief Testbench for Alu

--! Use standard library and import the packages (std_logic_1164,std_logic_unsigned,std_logic_arith)

library IEEE;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

use ieee.std_logic_arith.all;

--! Use CPU Definitions package

use work.pkgOpenCPU32.all;

ENTITY testAlu IS

END testAlu;

--! @brief Alu Testbench file

--! @details Exercise each Alu operation to verify if the description work as planned 

--! for more information: http://vhdlguru.blogspot.com/2010/03/how-to-write-testbench.html

ARCHITECTURE behavior OF testAlu IS

         --! Component declaration to instantiate the Alu circuit

    COMPONENT Alu

    generic (n : integer := nBits - 1);                                 --! Generic value (Used to easily change the size of the Alu on the package)

         Port ( A : in  STD_LOGIC_VECTOR (n downto 0);           --! Alu Operand 1

           B : in  STD_LOGIC_VECTOR (n downto 0);                --! Alu Operand 2

           S : out  STD_LOGIC_VECTOR (n downto 0);               --! Alu Output

           sel : in  aluOps);                                                                   --! Select operation

    END COMPONENT;

   --Inputs

   signal A : std_logic_vector((nBits - 1) downto 0) := (others => '0');  --! Wire to connect Test signal to component

   signal B : std_logic_vector((nBits - 1) downto 0) := (others => '0');  --! Wire to connect Test signal to component

   signal sel : aluOps := alu_sum;                                                                                                              --! Wire to connect Test signal to component

        --Outputs

   signal S : std_logic_vector((nBits - 1) downto 0);                                                            --! Wire to connect Test signal to component

BEGIN

        --! Instantiate the Unit Under Test (Alu) (Doxygen bug if it's not commented!)

   uut: Alu PORT MAP (

          A => A,

          B => B,

          S => S,

          sel => sel

        );

   --! Process that will stimulate all of the Alu operations

   stim_proc: process

   begin

      -- Pass ---------------------------------------------------------------------------

                wait for 1 ps;

                REPORT "Pass input A to output" SEVERITY NOTE;

                sel <= alu_pass;

                A <= conv_std_logic_vector(22, nBits);

                wait for 1 ns;  -- Wait to stabilize the response

                assert S = (A ) report "Invalid Pass output" severity FAILURE;

                -- AND ---------------------------------------------------------------------------

                wait for 1 ps;

                REPORT "AND without carry 2(10) AND 3(11)" SEVERITY NOTE;

                sel <= alu_and;

                A <= conv_std_logic_vector(2, nBits);

                B <= conv_std_logic_vector(3, nBits);

                wait for 1 ns;  -- Wait to stabilize the response

                assert S = (A and B) report "Invalid AND output" severity FAILURE;

                -- OR ---------------------------------------------------------------------------

                wait for 1 ns;

                REPORT "OR without carry 5 OR 7" SEVERITY NOTE;

                sel <= alu_or;

                A <= conv_std_logic_vector(5, nBits);

                B <= conv_std_logic_vector(7, nBits);

                wait for 1 ns;  -- Wait to stabilize the response

                assert S = (A or B) report "Invalid OR output" severity FAILURE;

                -- XOR ---------------------------------------------------------------------------

                wait for 1 ns;

                REPORT "OR without carry 11 XOR 9" SEVERITY NOTE;

                sel <= alu_xor;

                A <= conv_std_logic_vector(11, nBits);

                B <= conv_std_logic_vector(9, nBits);

                wait for 1 ns;  -- Wait to stabilize the response

                assert S = (A xor B) report "Invalid XOR output" severity FAILURE;

                -- NOT ---------------------------------------------------------------------------

                wait for 1 ns;

                REPORT "NOT 10" SEVERITY NOTE;

                sel <= alu_not;

                A <= conv_std_logic_vector(10, nBits);

                B <= (others => 'X');

                wait for 1 ns;  -- Wait to stabilize the response

                assert S = (not A) report "Invalid NOT output" severity FAILURE;

      wait;

   end process;

END;