VHDLのLOG2を完全マスター！10のサンプルコードで理解

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;

entity log2_example is
end log2_example;

architecture behavior of log2_example is
begin
    process
    variable result : real;
    begin
        result := log2(8);
        report "LOG2(8) is " & real'image(result);
        wait;
    end process;
end behavior;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;

entity log2_calc is
    Port ( input : in  real;
           output : out  real);
end log2_calc;

architecture Behavioral of log2_calc is
begin
process (input)
begin
    output <= log2(input);
end process;
end Behavioral;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;

entity log2_sum is
    Port ( input1 : in  real;
           input2 : in  real;
           output : out  real);
end log2_sum;

architecture Behavioral of log2_sum is
begin
process (input1, input2)
begin
    output <= log2(input1) + log2(input2);
end process;
end Behavioral;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;

entity log2_analysis is
    Port ( data_input : in  real;
           threshold : in real;
           result : out  boolean);
end log2_analysis;

architecture Behavioral of log2_analysis is
begin
process (data_input, threshold)
begin
    if log2(data_input) >= threshold then
        result <= true;
    else
        result <= false;
    end if;
end process;
end Behavioral;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity exp_calc is
    Port ( X : in  STD_LOGIC_VECTOR(3 downto 0);
           Y : out STD_LOGIC_VECTOR(7 downto 0));
end exp_calc;

architecture Behave of exp_calc is
begin
    Y <= "1" & X after 10 ns; -- 2のX乗を計算
end Behave;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity signal_process is
    Port ( signal_in : in  STD_LOGIC_VECTOR(7 downto 0);
           signal_out : out STD_LOGIC_VECTOR(7 downto 0));
end signal_process;

architecture Behave of signal_process is
    signal temp : STD_LOGIC_VECTOR(7 downto 0);
begin
    temp <= signal_in + "00000001" after 5 ns;
    signal_out <= temp after 5 ns;
end Behave;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity data_transfer is
    Port ( enable : in  STD_LOGIC;
           data_in : in  STD_LOGIC_VECTOR(7 downto 0);
           data_out : out STD_LOGIC_VECTOR(7 downto 0));
end data_transfer;

architecture Behave of data_transfer is
begin
    process(enable, data_in)
    begin
        if (enable = '1') then
            data_out <= data_in after 10 ns;
        else
            data_out <= (others => '0') after 10 ns;
        end if;
    end process;
end Behave;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity log2_system is
    Port ( input : in std_logic_vector(7 downto 0);
           output : out std_logic_vector(3 downto 0));
end log2_system;

architecture behavior of log2_system is
begin
    process(input)
    variable temp: integer := 0;
    variable result: integer := 0;
    begin
        -- 入力データを整数に変換
        temp := to_integer(input);

        -- LOG2計算
        while temp > 1 loop
            temp := temp / 2;
            result := result + 1;
        end loop;

        -- 結果を出力
        output <= to_std_logic_vector(result);
    end process;
end behavior;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity Log2Checker is
    Port ( val : in  STD_LOGIC_VECTOR(7 downto 0);
           log_result : out STD_LOGIC_VECTOR(7 downto 0);
           error : out STD_LOGIC);
end Log2Checker;

architecture Behavioral of Log2Checker is
begin
process(val)
    variable tmp_result: real;
begin
    if val = "00000000" or val(7) = '1' then
        -- 入力が0や負の数の場合
        error <= '1';
        log_result <= (others => '0');
    else
        tmp_result := log2(to_integer(val));
        log_result <= STD_LOGIC_VECTOR(to_unsigned(integer(tmp_result), 8));
        error <= '0';
    end if;
end process;
end Behavioral;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;

entity CustomLOG2 is
    Port ( input : in  STD_LOGIC_VECTOR(7 downto 0);
           output : out STD_LOGIC_VECTOR(7 downto 0));
end CustomLOG2;

architecture Behavior of CustomLOG2 is
begin
    process(input)
    variable result : real;
    begin
        -- LOG2の計算
        result := log2(real(to_integer(unsigned(input))));

        -- カスタマイズ部分: 入力が128以上の場合、LOG2の結果に2を足す
        if to_integer(unsigned(input)) >= 128 then
            result := result + 2.0;
        end if;

        output <= std_logic_vector(to_unsigned(integer(result), 8));
    end process;
end Behavior;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;

entity CustomVHDL is
    Port ( input_signal : in  STD_LOGIC_VECTOR(7 downto 0);
           output_signal : out STD_LOGIC_VECTOR(7 downto 0));
end CustomVHDL;

architecture Behavior of CustomVHDL is
begin
    process(input_signal)
    variable log_result : real;
    begin
        -- LOG2の計算
        log_result := log2(real(to_integer(unsigned(input_signal))));

        -- カスタマイズ部分: LOG2の結果を2倍して出力
        output_signal <= std_logic_vector(to_unsigned(integer(log_result * 2.0), 8));
    end process;
end Behavior;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;

entity SignalGenerator is
    Port ( input_amplitude : in  STD_LOGIC_VECTOR(7 downto 0);
           output_wave : out STD_LOGIC_VECTOR(7 downto 0));
end SignalGenerator;

architecture Behavior of SignalGenerator is
begin
    process(input_amplitude)
    variable amplitude_factor : real;
    begin
        -- LOG2の計算で振幅係数を取得
        amplitude_factor := log2(real(to_integer(unsigned(input_amplitude))));

        -- オリジナルの波形生成処理
        -- ここでは簡単のためにサイン波の生成を仮定
        output_wave <= std_logic_vector(to_unsigned(integer(sin(real(now) * 2.0 * 3.14159) * amplitude_factor), 8));
    end process;
end Behavior;