rs232.vhd

xilinx Sparten3E 串行通信及lcd字符显示

----------------------------------------------------------------------------------
-- Company: 
-- Engineer: 
-- 
-- Create Date:    13:12:18 12/11/2007 
-- Design Name: 
-- Module Name:    RS232 - Behavioral 
-- Project Name: 
-- Target Devices: 
-- Tool versions: 
-- Description: 
--
-- Dependencies: 
--
-- Revision: 
-- Revision 0.01 - File Created
-- Additional Comments: 
--
----------------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

---- Uncomment the following library declaration if instantiating
---- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity RS232 is
    Port ( send : inout std_logic;
			  rxd : in  STD_LOGIC;
           txd : out  STD_LOGIC;
			  lcd_e : out  STD_LOGIC;
           lcd_rw : out  STD_LOGIC;
           lcd_rs : out  STD_LOGIC;
           sf_d : out  STD_LOGIC_VECTOR (3 downto 0);
           clk : in  STD_LOGIC);
end RS232;

architecture Behavioral of RS232 is
signal sstart : std_logic :='0';
signal rstart : std_logic :='0';
signal lword : std_logic_vector(3 downto 0);
signal hword : std_logic_vector(3 downto 0);
signal state : integer range 0 to 7 := 0;
Type data is array (0 to 3, 0 to 1) of std_logic_vector(3 downto 0);
constant cmd : data := (("0010","1000"),--Function set
								  ("0000","0110"),--Entry mode set
								  ("0000","1100"),--Display on/off
								  ("1000","0000")--Set DDram address
								  );
signal index : integer range 0 to 4 :=0;
signal count2 : integer range 0 to 10 :=0;
signal count1 : integer range 0 to 10 :=0;
signal count0 : integer range 0 to 750000 := 0;
signal count3 : integer range 0 to 50000 :=0;
signal sflag : std_logic := '0';
signal flag : integer range 0 to 15 := 0;
signal a1,a2,a3,j,k: std_logic;
signal fclk : std_logic :='0';
signal srst : std_logic;
begin

process(clk)
begin
if rising_edge(clk) then

	if(state = 0) then --initializtion
		if(flag = 0) then
			if count0 = 750000 then
				flag <= 1;
				sf_d <= "0011";
				lcd_e <= '1';
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;
		elsif flag = 1 then
			if count0 = 12 then
				flag <= 2;
				lcd_e <= '0';
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;
		elsif flag = 2 then
			if count0 = 205000 then
				flag <= 3;
				sf_d <= "0011";
				lcd_e <= '1';
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;
		elsif flag = 3 then
			if count0 = 12 then
				flag <= 4;
				lcd_e <= '0';
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;
		elsif flag = 4 then
			if count0 = 5000 then
				flag <= 5;
				sf_d <= "0011";
				lcd_e <= '1';
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;	
		elsif flag = 5 then
			if count0 = 12 then
				flag <= 6;
				lcd_e <= '0';
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;	
		elsif flag = 6 then
			if count0 = 2000 then
				flag <= 7;
				sf_d <= "0010";
				lcd_e <= '1';
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;	
		elsif flag = 7 then
			if count0 = 12 then
				flag <= 8;
				lcd_e <= '0';
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;	
		else
			if count0 = 2000 then
				flag <= 0;
				count0 <= 0;
				state <= 1;
				lcd_rs <= '0';
				lcd_rw <= '0';
				sf_d <= cmd(index,0);--the high 4bits
			else
				count0 <= count0+1;
			end if;				
		end if;
-----------------------------------------------------------------------		
	elsif state = 1 then	--send command
		if flag = 0 then	   --delay 40ns
			if count0 = 2 then
				flag <= 1;
				count0 <= 0;
				lcd_e <= '1';   
			else
				count0 <= count0+1;
			end if;
		elsif flag = 1 then  --delay 230ns
			if count0 = 12 then
				flag <= 2;
				lcd_e <= '0';
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;
		elsif flag = 2 then --delay 20ns
			if count0 = 1 then
				if sflag = '0' then --the word is not finished					
					flag <= 3;
				else
					flag <= 4; 
				end if;
				lcd_rw <= '1';
				count0 <= 0;				
			else
				count0 <= count0+1;
			end if;
		elsif flag = 3 then --delay 1us,low 4bits
			if count0 = 50 then
				sflag <= '1';
				flag <= 0;
				lcd_rw <= '0';
				count0 <= 0;
				sf_d <= cmd(index,1);
				index <= index+1;
			else
				count0 <= count0+1;
			end if;
		elsif flag = 4 then --delay 40us, the word is finished
			if count0 = 2000 then
				sflag <= '0';
				flag <= 0;
				lcd_rw <= '0';
				count0 <= 0;
				if index = 4 then
					lcd_rs <= '1';
					state <= 2;
				else
					sf_d <= cmd(index,0);
				end if;
			else
				count0 <= count0+1;
			end if;
		end if;
-------------------------------------------------------------------------		
	elsif state = 2 then --waiting
		if (rxd = '0' or rstart = '1') then --receive data start bit	
			if count1 = 0 then
				rstart <= '1';
				state <= 3;
			elsif count1=10 then --transfer finished no specific bit
				sf_d <= hword;
				count1 <= 0;
				rstart <= '0';
				state <= 4;	
			elsif (count1>0 and count1<5) then--low 4bits
				lword(count1-1) <= rxd;
				state <= 3;	
			elsif (count1>4 and count1<9) then --high 4bits
				hword(count1-5) <= rxd;
				state <= 3;	
			else
				state <= 3;	
			end if;	
		end if;
		
		if srst ='1' then 
			sstart <= '1';
		end if;
		
		if (sstart = '1' and srst = '1') then
			if count2 = 0 then
				txd <= '0';
				state <= 3;
			elsif count2 = 10 then
				count2 <= 0;
				sstart <= '0';
			elsif count2 = 9 then
				txd <= '1';
				state <= 3;
			elsif (count2>0 and count2<5) then--low 4bits
				txd <= lword(count2-1);
				state <= 3;	
			elsif (count2>4 and count2<9) then --high 4bits
				txd <= hword(count2-5);
				state <= 3;	
			else
				state <= 3;	
			end if;
		end if;
-------------------------------------------------------------------------	
	elsif state = 3 then --delay 5210 cycles
			if count0 = 5210 then
				count1 <= count1+1;
				state <= 2;
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;
---------------------------------------------------------------------------			
	elsif state = 4 then --send characters
		if flag = 0 then	   --delay 40ns
			if count0 = 2 then
				flag <= 1;
				count0 <= 0;
				lcd_e <= '1';
			else
				count0 <= count0+1;
			end if;
		elsif flag = 1 then  --delay 230ns
			if count0 = 12 then
				flag <= 2;
				lcd_e <= '0';
				count0 <= 0;
			else
				count0 <= count0+1;
				end if;
		elsif flag = 2 then --delay 20ns
			if count0 = 1 then
				if sflag = '0' then --the word is not finished				
					flag <= 3;
				else
					flag <= 4; 
				end if;
				lcd_rw <= '1';
				count0 <= 0;				
			else
				count0 <= count0+1;
			end if;
		elsif flag = 3 then --delay 1us,low 4bits
			if count0 = 50 then
				sflag <= '1';
				flag <= 0;
				lcd_rw <= '0';
				count0 <= 0;
				sf_d <= lword ;
			else
				count0 <= count0+1;
			end if;
		elsif flag = 4 then --delay 40us
			if count0 = 2000 then
				sflag <= '0';
				flag <= 0;
				lcd_rw <= '0';
				state <= 2;
				count0 <= 0;
			else
				count0 <= count0+1;
			end if;
		end if;		
	end if;
	
	if count3 = 50000 then --button filter 
		count3 <= 0;
		fclk <= not fclk;
	else
		count3 <= count3+1;
	end if;

end if;
end process;

process(fclk)
begin
if rising_edge(fclk) then
	a1 <= send;
	a2 <= a1;
	a3 <= a2;
	j <= a1 and a2 and a3;
	k <= not(a1 or a2 or a3);
	srst <= (j and not srst)or(not k and srst);
end if;
end process;

end Behavioral;