lcd_vhdl2.vhdl

用VHDL来实现LCD1602的驱动（实验过）

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity LCD is
port(	clk:in std_logic;
    	rs: out std_logic;
    	rw: out std_logic;
    	en: out std_logic;
    	data: out std_logic_vector(7 downto 0));
end LCD;

architecture Behavioral of LCD is
type datatype is array (0 to 15) of std_logic_vector(7 downto 0);
CONSTANT WELLCOME : datatype :=("01010100","01111000","01111001","00100000",
                                "00100000","00100000","00100000","00100000",
            					"00100000","00100000","00100000","00100000",
           					    "01000011","01010000","01001100","01000100" );
        
type statetype is(s1,s2,s3,s4);
signal state    :statetype;  
signal datacnt  :integer range 0 to 15;
signal b		:integer range 0 to 12499;
signal bc       :std_logic; 
signal ck       :std_logic;

begin
process(clk)
begin
  if rising_edge(clk) then
   		if b=12499 then
   			 b<=0;
   		else
    		 b<=b+1;
   		end if;
  end if;
  if b<6249 then
   		bc<='1';
  else
   		bc<='0';
  end if;
end process;

process(bc)
variable s:integer range 0 to 7;
begin
  if rising_edge(bc) then
   		if s=7 then
    		s:=0;
   		else
    		s:=s+1;
   		end if;
  end if;  
  if s<4 then
   		ck<='0';
  else
   		ck<='1';
  end if;
end process;

process(ck,state)
begin
  	if rising_edge(ck) then
   		case state is
    			when s1=>
     					rs<='0';
					    if(datacnt=0)then
      						data<="00000110";             ///////传送的是命令0x06
      						datacnt<=datacnt+1;
     					elsif(datacnt=1)then
      						data<="00001100";             ///////传送的是命令0X0C
      						datacnt<=datacnt+1;
     					elsif(datacnt=2)then
      						data<="00111000";             /////// 传送的是吗命令0X38
      						datacnt<=datacnt+1;
     					else
      						data<="10000000";            //////// 传送 的是0X80;
      						datacnt<=0;
      						state<=s2;
     					end if;
    			when s2=>
     					rs<='1';
     					if datacnt=15 then
      						state <= s3;    
      						data <= WELLCOME(datacnt);
      						datacnt<=0;
     					else
      						state <= s2;       
      						data <= WELLCOME(datacnt);    /////// 把数组中的数据送入液晶控制模块进行显示
      						datacnt<=datacnt+1;
     					end if;
    			when s3=>
						rs<='0';
     					data<="11000000";                 ///////  传递的是命令0XC0;
     					state<=s4;
    			when s4=>
     					rs<='1';
     					if datacnt=15 then              //////// 回到出示状态进行显示
      						state <= s1;    
      						data <= WELLCOME(datacnt);   
      						datacnt<=0;
     					else
      						state <= s4;       
      						data <= WELLCOME(datacnt);   ////////  于第二行中显示数据
     						 datacnt<=datacnt+1;
     					end if;
    			when others=>state<=s1;
   			end case;
  		end if;
end process;

rw<='0';
en<=ck;
-- ckout<=ck;
end Behavioral;