频率计.txt

频率计

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity freq is
port	(xclk,clk:		in  std_logic;
		A0,B0,C0,D0,A1,B1,C1,D1:out std_logic;
		A2,B2,C2,D2,A3,B3,C3,D3:out std_logic);
end;

architecture example of freq is
signal	countb:std_logic_vector(3 downto 0);
signal	count0:std_logic_vector(3 downto 0);
signal	count1:std_logic_vector(3 downto 0);
signal	count2:std_logic_vector(3 downto 0);
signal	count3:std_logic_vector(3 downto 0);
signal	en,clr,m0,m1,m2:std_logic;

begin
	P1:process(xclk,en,clr)
	begin
		if(clr='0') then
			count0<="0000";
	m0<='0';
		elsif((en='1') and  rising_edge (xclk) ) then
			if( count0="1001") then
			count0<="0000";
	m0<='0';
			else
			count0<=count0 + '1';
	m0<='1';
			end if;	
		end if;	
	end process P1;

	P2:process(en,clr,m0)
	begin
		if(clr='0') then
			count1<="0000";
	m1<='0';
		elsif((en='1') and falling_edge(m0) ) then
			if( count1="1001") then
			count1<="0000";
	m1<='0';
			else
			count1<=count1 + '1';
	m1<='1';
			end if;	
		end if;	
	end process P2;

	P3:process(en,clr,m1)
	begin
		if(clr='0') then
			count2<="0000";	m2<='0';
		elsif((en='1') and   falling_edge(m1) ) then
			if( count2="1001") then
			count2<="0000";
	m2<='0';
			else
			count2<=count2 + '1';
	m2<='1';
			end if;	
		end if;	
	end process P3;

	P4:process(en,clr,m2)
	begin
		if(clr='0') then
			count3<="0000";
		elsif((en='1') and   falling_edge(m2) ) then
			if( count3="1001") then
			count3<="0000";
			else
			count3<=count3 + '1';
			end if;	
		end if;	
	end process P4;

	P5:process(clk)
	begin
		if(rising_edge (clk) )then
			countb<=countb+'1';
			else
			countb<=countb;
		end if;

		if (countb="0111") then
			clr <= '0';
		else
			clr <= '1';
		end if;

		if (countb>"0111") then
			en<='1';
		else
			en<='0';
		end if;
	end process P5;
A0<=count0(0);B0<=count0(1);C0<=count0(2);D0<=count0(3);
A1<=count1(0);B1<=count1(1);C1<=count1(2);D1<=count1(3);
A2<=count2(0);B2<=count2(1);C2<=count2(2);D2<=count2(3);
A3<=count3(0);B3<=count3(1);C3<=count3(2);D3<=count3(3);
end example;