IntMult.vhd

library IEEE;
use IEEE.std_logic_1164.all;
--use IEEE.std_logic_arith.all;
use IEEE.std_logic_misc.all;
use IEEE.std_logic_unsigned.all;

entity IntMult is
    Port (  Clk_in: IN STD_LOGIC;
                async_rst: IN STD_LOGIC;
                mult_start_in: IN STD_LOGIC;
                multiplicand_in: IN STD_LOGIC_VECTOR(3 DOWNTO 0);
                multiplier_in: IN STD_LOGIC_VECTOR(3 DOWNTO 0);
                mult_result_out: OUT STD_LOGIC_VECTOR(7 DOWNTO 0);
                mult_ready_out: OUT STD_LOGIC);
end IntMult;

architecture Behavioral of IntMult is
    begin
    Main: process(Clk_in, async_rst)
    variable count : STD_LOGIC_VECTOR (2 DOWNTO 0);
     variable Q : STD_LOGIC_VECTOR(7 DOWNTO 0);
     variable M : STD_LOGIC_VECTOR(3 DOWNTO 0);
     variable C : STD_LOGIC_VECTOR(7 DOWNTO 0);
     variable A : STD_LOGIC_VECTOR(7 DOWNTO 0);
        begin
            if async_rst = '1' then
            count := "000";
            Q := "00000000";
            M := "0000";
            A := "00000000";
            elsif Rising_Edge(Clk_in) then
                if mult_start_in = '1' then
                    count := "000";
                    Q := "0000" + multiplier_in;
                    M := multiplicand_in;
                    C := "00000000";
                    A := "00000000";
                    mult_result_out <= A;
                    mult_ready_out <= '0';
                elsif count = "000" then
                    mult_ready_out <= '0';
                    if M(0) = '1' then
                        A := A + Q;
                    end if;
                    mult_result_out <= A;
                    count := count + 1;
                    Q(7 DOWNTO 1) := Q(6 DOWNTO 0) + '0';
                elsif count = "001" then
                    mult_ready_out <= '0';
                    if M(1) = '1' then
                        A := A + Q;
                    end if;
                    mult_result_out <= A;
                    count := count + 1;
                    Q(7 DOWNTO 1) := Q(6 DOWNTO 0) + '0';
                elsif count = "010" then
                    mult_ready_out <= '0';
                    if M(2) = '1' then
                        A := A + Q;
                    end if;
                    mult_result_out <= A;
                    count := count + 1;
                    Q(7 DOWNTO 1) := Q(6 DOWNTO 0) + '0';
                elsif count = "011" then
                    mult_ready_out <= '0';
                    if M(3) = '1' then
                        A := A + Q;
                    end if;
                    mult_result_out <= A;
                    count := count + 1;
                elsif count = "100" then
                    A := A + Q;
                    A := not A;
                    mult_ready_out <= '1';
                    mult_result_out <= A;
                    count := count + 1;
                end if;
            end if;
        end process Main;
end Behavioral;