delta.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 delta IS
      PORT(clk0,fq:IN STD_LOGIC; 
        q:OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
end delta;
ARCHITECTURE behave OF delta IS
signal i:integer range 0 to 20;
	signal clk2:std_logic;
	BEGIN
		process(fq,clk0)
			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)
 VARIABLE tmp:STD_LOGIC_VECTOR(7 DOWNTO 0); 
  VARIABLE a:STD_LOGIC; 
BEGIN
IF clk2'EVENT AND clk2='1' THEN
 IF a='0' THEN
 IF tmp="11111110" THEN
tmp:="11111111"; 
a:='1'; 
 ELSE           
tmp:=tmp+1;
 END IF; 
 ELSE
 IF tmp ="00000001" THEN
tmp:="00000000"; 
a:='0';
 ELSE   
tmp:=tmp-1;
 END IF; 
 END IF; 
END IF; 
q<=tmp; 
END PROCESS;
END behave;