VHDL固定小数点活用法！10の実用サンプルコード

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

type fixed_point is range -8 to 7.9999 with delta 0.0001;
signal a, b, c : fixed_point;

a <= b + c;
c <= a - b;

signal isEqual : boolean;
...
isEqual <= (a = b);

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.FIXED_PKG.ALL;

entity FilterDesign is
    Port ( clk : in STD_LOGIC;
           input_signal : in SIGNED(15 downto 0);
           output_signal : out SIGNED(15 downto 0));
end FilterDesign;

architecture Behavioral of FilterDesign is
    signal filter_coeff : SFIXED(7 downto -8);
    signal temp_result : SFIXED(15 downto 0);
begin
    -- ここではフィルタ係数を0.5としています
    filter_coeff <= "0.10000000000000"; 

    process(clk)
    begin
        if rising_edge(clk) then
            temp_result <= input_signal * filter_coeff;
            output_signal <= temp_result;
        end if;
    end process;

end Behavioral;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.FIXED_PKG.ALL;

entity AudioAmplifier is
    Port ( clk : in STD_LOGIC;
           audio_input : in SIGNED(15 downto 0);
           audio_output : out SIGNED(15 downto 0));
end AudioAmplifier;

architecture Behavioral of AudioAmplifier is
    signal amplification_factor : SFIXED(1 downto 0);
begin
    -- ここでは増幅係数を2としています
    amplification_factor <= "10"; 

    process(clk)
    begin
        if rising_edge(clk) then
            audio_output <= audio_input * amplification_factor;
        end if;
    end process;

end Behavioral;

-- 注意: 実際の画像処理では、画像のデータ構造や読み込みなどの詳細な処理が必要ですが、ここでは明るさの調整のみを表しています。

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.FIXED_PKG.ALL;

entity ImageBrightnessAdjust is
    Port ( clk : in STD_LOGIC;
           pixel_input : in SIGNED(7 downto 0); -- 8ビットの画像データを想定
           pixel_output : out SIGNED(7 downto 0));
end ImageBrightnessAdjust;

architecture Behavioral of ImageBrightnessAdjust is
    signal brightness_factor : SFIXED(1 downto -6);
begin
    -- 明るさを1.5倍に調整
    brightness_factor <= "1.100000"; 

    process(clk)
    begin
        if rising_edge(clk) then
            pixel_output <= pixel_input * brightness_factor;
        end if;
    end process;

end Behavioral;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity FixedPointAdder is
    Port ( A : in  signed(7 downto 0);
           B : in  signed(7 downto 0);
           Result : out signed(7 downto 0));
end FixedPointAdder;

architecture Behavioral of FixedPointAdder is
begin
    process(A, B)
    begin
        Result <= A + B;  -- ２つの固定小数点数を加算
    end process;

end Behavioral;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
use IEEE.FIXED_PKG.ALL;

entity control_system is
    Port ( input : in SFIXED(7 downto -8); -- 16-bit fixed-point number
           output : out SFIXED(7 downto -8));
end control_system;

architecture Behavioral of control_system is
    signal feedback : SFIXED(7 downto -8);
    constant K : SFIXED(7 downto -8) := "01111111.10000000"; -- Gain constant
begin
    process(input)
    begin
        feedback <= input * K; -- Multiply input by gain
        output <= feedback;    -- Output the feedback value
    end process;
end Behavioral;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity FixedPointOptimization is
  Port ( clk : in STD_LOGIC;
         data_in : in signed(15 downto 0);
         result_out : out signed(15 downto 0) );
end FixedPointOptimization;

architecture Behavioral of FixedPointOptimization is
  signal tmp_result : signed(15 downto 0);
begin
  process(clk)
  begin
    if rising_edge(clk) then
      -- 固定小数点計算の最適化部分
      tmp_result <= data_in + "0010101001010101"; -- 例: ある定数との加算
    end if;
  end process;

  result_out <= tmp_result;

end Behavioral;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity MixedFixedFloat is
end MixedFixedFloat;

architecture Behavior of MixedFixedFloat is
    signal fixed_value : sfixed(7 downto -8);
    signal float_value : real;
    signal result : sfixed(7 downto -8);
begin
    -- 固定小数点と浮動小数点の変換
    process
    begin
        fixed_value <= to_sfixed(3.14, fixed_value);
        float_value <= to_real(fixed_value);
        result <= to_sfixed(float_value, result);
        wait;
    end process;
end Behavior;