square.vhd.bak

能够产生方波、三角波、正弦波、及阶梯波

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY square IS
  PORT(clk0,fq:IN STD_LOGIC;
       q:OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
END;
ARCHITECTURE behave OF square IS 
  SIGNAL Q1:STD_LOGIC_VECTOR(2 DOWNTO 0);
   signal i:integer range 0 to 20;
	signal clk2:std_logic;
	BEGIN
		process(fq) 
			begin
			  if fq'event and fq='1' then
				if i<20 then i<=i+2;
				else i<=0;
				end if;
			   end if;
				
			END PROCESS;
		process(i,clk0)
			variable tem:integer range 0 to 22;
			variable qq:std_logic;
			begin
				if clk0'event and clk0='1' then
						if tem<i then tem:=tem+1;
							else tem:=0;qq:=not qq;
						end if;
				end if;
				clk2<=qq;
			end process;
   PROCESS(clk2)
       BEGIN
          IF clk2'EVENT AND clk2='1' THEN
                Q1<=Q1+1;
          END IF;
   END PROCESS;
   q<="11111111" WHEN Q1(2)='1' ELSE
         q<="00000000" ;
END;