pwm18.vhd

这个是国外大学的项目代码

------------------------------------------------------------------------
--  pwm2x.vhd -- Pulse Width Modulator
------------------------------------------------------------------------
--  Author : Kovacs Laszlo - Attila 
------------------------------------------------------------------------
-- Software version: Xilinx ISE 7.1.04i
--                   WebPack
------------------------------------------------------------------------
-- This Pulse Width Modulator according to the 6 most significant bits 
-- of the data input selects one of the 32 logics (pulse widths).
------------------------------------------------------------------------

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

entity pwm18 is
    Port ( CLK2X : in std_logic;
           CLK   : in std_logic;
           CLK2  : in std_logic;
           CLK4  : in std_logic;
           CLK8  : in std_logic;
           DO    : out std_logic;
           DI    : in std_logic_vector(7 downto 0));
end pwm18;

architecture Behavioral of pwm18 is

signal pwmsel, pwmsel2 : std_logic_vector(4 downto 0) := "00000";
signal pwmsel3 : std_logic_vector(3 downto 0) := "0000";

begin
    
    pwmsel(4) <= DI(7);
    pwmsel(3 downto 0) <= pwmsel3 when DI(7) = '1' else not pwmsel3;
    pwmsel2 <= DI(6 downto 2) when DI(7) = '1' else not DI(6 downto 2);

    with pwmsel2(4 downto 0) select
    pwmsel3
           <= "1111" when "11111",
              "1111" when "11110",
              "1111" when "11101",
              "1111" when "11100",
              "1111" when "11011",
              "1110" when "11010",
              "1110" when "11001",
              "1110" when "11000",
              "1110" when "10111",
              "1101" when "10110",
              "1101" when "10101",
              "1101" when "10100",
              "1100" when "10011",
              "1100" when "10010",
              "1011" when "10001",
              "1011" when "10000",
              "1010" when "01111",
              "1010" when "01110",
              "1001" when "01101",
              "1001" when "01100",
              "1000" when "01011",
              "1000" when "01010",
              "0111" when "01001",
              "0111" when "01000",
              "0110" when "00111",
              "0110" when "00110",
              "0101" when "00101",
              "0100" when "00100",
              "0011" when "00011",
              "0010" when "00010",
              "0001" when "00001",
              "0000" when others;

    with pwmsel select
    DO <= '1'                                       when "11111",--32
        CLK8 or CLK4 or CLK2 or CLK or CLK2X        when "11110",--31
        CLK8 or CLK4 or CLK2 or CLK                 when "11101",--30
        CLK8 or CLK4 or CLK2 or (CLK and CLK2X)     when "11100",--29
        CLK8 or CLK4 or CLK2                        when "11011",--28
        CLK8 or CLK4 or (CLK2 and (CLK or CLK2X))   when "11010",--27
        CLK8 or CLK4 or (CLK2 and CLK)              when "11001",--26
        CLK8 or CLK4 or (CLK2 and CLK and CLK2X)    when "11000",--25
        CLK8 or CLK4                                when "10111",--24
        CLK8 or (CLK4 and (CLK2 or CLK or CLK2X))   when "10110",--23
        CLK8 or (CLK4 and (CLK2 or CLK))            when "10101",--22
        CLK8 or (CLK4 and (CLK2 or (CLK and CLK2X)))when "10100",--21
        CLK8 or (CLK4 and CLK2)                     when "10011",--20
        CLK8 or (CLK4 and CLK2 and (CLK or CLK2X))  when "10010",--19
        CLK8 or (CLK4 and CLK2 and CLK)             when "10001",--18
        CLK8 or (CLK4 and CLK2 and CLK and CLK2X)   when "10000",--17
        CLK8                                        when "01111",--16
        CLK8 and (CLK4 or CLK2 or CLK or CLK2X)     when "01110",--15
        CLK8 and (CLK4 or CLK2 or CLK)              when "01101",--14
        CLK8 and (CLK4 or CLK2 or (CLK and CLK2X))  when "01100",--13
        CLK8 and (CLK4 or CLK2)                     when "01011",--12
        CLK8 and (CLK4 or (CLK2 and (CLK or CLK2X)))when "01010",--11
        CLK8 and (CLK4 or (CLK2 and CLK))           when "01001",--10
        CLK8 and (CLK4 or (CLK2 and CLK and CLK2X)) when "01000",--09
        CLK8 and CLK4                               when "00111",--08
        CLK8 and CLK4 and (CLK2 or CLK or CLK2X)    when "00110",--07
        CLK8 and CLK4 and (CLK2 or CLK)             when "00101",--06
        CLK8 and CLK4 and (CLK2 or (CLK and CLK2X)) when "00100",--05
        CLK8 and CLK4 and CLK2                      when "00011",--04
        CLK8 and CLK4 and CLK2 and not CLK          when "00010",--03
        CLK8 and CLK4 and CLK2 and CLK2X            when "00001",--01
        '0'                                         when others; --00

end Behavioral;