vhdl 实现二进制转8421bcd

可以使用以下代码实现二进制转8421BCD：

library ieee;
use ieee.std_logic_1164.all;

entity bin_to_bcd is
    port (
        bin : in std_logic_vector(3 downto );
        bcd : out std_logic_vector(7 downto )
    );
end bin_to_bcd;

architecture Behavioral of bin_to_bcd is
begin
    process(bin)
    begin
        case bin is
            when "000" => bcd <= "00000000";
            when "0001" => bcd <= "00000001";
            when "001" => bcd <= "00000010";
            when "0011" => bcd <= "00000011";
            when "010" => bcd <= "00000100";
            when "0101" => bcd <= "00000101";
            when "011" => bcd <= "00000110";
            when "0111" => bcd <= "00000111";
            when "100" => bcd <= "00001000";
            when "1001" => bcd <= "00001001";
            when others => bcd <= "11110000";
        end case;
    end process;
end Behavioral;

以上代码将四位二进制数转换为八位8421BCD码。