pwm.vhd

用 硬件描述语言实现脉宽调制 VHDL 例子

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

ENTITY PWM_vs_Sigma_Delta_v2 is
    generic( N:   natural := 4;
	          Max: natural := 16);
    Port ( Clk :  in  STD_LOGIC;
	        Scale: in  STD_LOGIC;
           PCM :  in  STD_LOGIC_VECTOR (N-1 downto 0);
           PWM :  out  STD_LOGIC;
           PPM :  out  STD_LOGIC);  -- or SD
end PWM_vs_Sigma_Delta_v2;

ARCHITECTURE Behavioral of PWM_vs_Sigma_Delta_v2 is
   signal PWM_Count:  STD_LOGIC_VECTOR (N-1 downto 0) := (others=>'0');
   signal Sigma: 		 STD_LOGIC_VECTOR (  N downto 0) := (others=>'0');
   signal Delta: 		 STD_LOGIC_VECTOR (  N downto 0) := (others=>'0');
	signal Scaled_clk: STD_LOGIC;	
begin

   process( Clk, Scale)
		variable Scalex:	     integer;
		constant Scale100msek: integer   :=   1; --5000;
		constant Scale500msek: integer   :=   0; --25000;
		variable Count:  integer range 0 to 50000001 := 0;
	begin	   
	   if Scale='1' then
         Scalex := Scale100msek; 
		else 
         Scalex := Scale500msek;
		end if;
		
	   if rising_edge(Clk)then
			if Count>=Scalex then
			   Scaled_clk <= '1';
				Count      := 0;
			else
			   Scaled_clk <= '0';
				Count      := Count+1;			
			end if;
		end if;
   end process;
	
	PWM_Generator: process( Clk, PWM_Count, PCM)
	begin
	   if rising_edge(Clk) then
		   if Scaled_Clk='1' then
			   if PWM_Count<Max-1 then
		         PWM_Count <= PWM_Count+1;
				else
               PWM_Count <= (others => '0');	
            end if;					
			end if;
		end if;
	   
	   if PWM_Count<PCM then
		   PWM <= '1';
		else
		   PWM <= '0';
		end if;
	end process PWM_Generator;	
	
	Delta <= '0'&PCM;	
   Sigma_Delta_Generator: process( Clk)
	begin
	   if rising_edge(Clk) then
		   if Scaled_Clk='1' then
				if Sigma<Max then
					PPM   <= '0';
					Sigma <= Sigma+Delta;	
				else
					PPM   <= '1';
					Sigma <= Sigma+Delta-conv_std_logic_vector(Max,N+1);
				end if;
			end if;
		end if;
	end process Sigma_Delta_Generator;	
		
end Behavioral;