---------------------------------------------------------------
-- Test Bench for GCD Calculator (ESD book Figure 2.9)
-- by Weijun Zhang, 04/2001
--
-- three cases tested
---------------------------------------------------------------

Library ieee;
use ieee.std_logic_1164.all;	   
use ieee.std_logic_arith.all;
use work.all;

entity test_GCD is			-- entity declaration
end test_GCD;

----------------------------------------------------------------

architecture Bench of test_GCD is

component gcd
port(	clk: 	in std_logic;
	rst:	in std_logic;
	go_i:	in std_logic;
	x_i:	in unsigned(3 downto 0);
	y_i:	in unsigned(3 downto 0);
	d_o:	out unsigned(3 downto 0)
);
end component;

signal T_clk,T_rst,T_go_i: std_logic;
signal T_x_i, T_y_i, T_d_o: unsigned(3 downto 0);

begin

    U1: GCD port map(T_clk,T_rst,T_go_i,T_x_i,T_y_i,T_d_o);
	
    Clk_sig: process
    begin
        T_clk<='1';			-- clock signal
        wait for 5 ns;
        T_clk<='0';
        wait for 5 ns;
    end process;

    process	

	variable err_cnt: integer :=0 ;

    begin
	
        -- case 1: input 0C & 80, output should be 4 
        T_rst<='1';
        T_go_i<='0';
        T_x_i<="1100";		
        T_y_i<="1000";
        wait for 20 ns;
	
        T_rst<='0';
        wait for 30 ns;
        T_go_i<='1';
        wait for 200 ns;						  
        assert(T_d_o=4) report "Error1" severity error;
	if (T_d_o/=4) then
	    err_cnt := err_cnt + 1;
	end if;

        -- case 2: input 0C & 02, output should be 2
        T_rst<='1';
        T_go_i<='0';
        T_x_i<="1100";
        T_y_i<="0010";
        wait for 20 ns;
	
        T_rst<='0';
        wait for 30 ns;
        T_go_i<='1';
        wait for 200 ns;						  
        assert(T_d_o=2) report "Error2" severity error;
	if (T_d_o/=2) then
	    err_cnt := err_cnt + 1;
	end if;
	    
        -- case 3: input 05 & 0A, output should be 5 
        T_rst<='1';
        T_go_i<='0';
        T_x_i<="0101";		
        T_y_i<="1010";
        wait for 20 ns;
	
        T_rst<='0';
        wait for 30 ns;
        T_go_i<='1';
        wait for 200 ns;						  
        assert(T_d_o=5) report "Error2" severity error;
	if (T_d_o/=5) then
	    err_cnt := err_cnt + 1;
	end if;

	-- summary of all the tests to see if any error
	if (err_cnt=0) then 			
	    assert false 
	    report "Testbench of GCD completed successfully!" 
	    severity note; 
	else 
	    assert true 
	    report "Something wrong, try again" 
	    severity error; 
	end if; 

        wait;

    end process;

end Bench;

-----------------------------------------------------------------
configuration CFG_TB of test_GCD is
	for Bench
	end for;
end CFG_TB;
-----------------------------------------------------------------