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LCD（1602）显示字符：需要两个VHD文件：
文件1代码 charlcd1：
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity charlcd1 is
Port ( clk : in std_logic; --24MHZ
Reset : in std_logic;
lcd_rs : out std_logic;
lcd_rw : out std_logic;
lcd_e : buffer std_logic;
data : out std_logic_vector(7 downto 0);
-- stateout: out std_logic_vector(10 downto 0);
clk_out: out std_logic);
end charlcd1;

architecture Behavioral of charlcd1 is

constant IDLE : std_logic_vector(10 downto 0) :="00000000000";
constant CLEAR : std_logic_vector(10 downto 0) :="00000000001";
constant RETURNCURSOR : std_logic_vector(10 downto 0) :="00000000010" ;
constant SETMODE : std_logic_vector(10 downto 0) :="00000000100";
constant SWITCHMODE : std_logic_vector(10 downto 0) :="00000001000";
constant SHIFT : std_logic_vector(10 downto 0) :="00000010000";
constant SETFUNCTION : std_logic_vector(10 downto 0) :="00000100000";
constant SETCGRAM : std_logic_vector(10 downto 0) :="00001000000";
constant SETDDRAM : std_logic_vector(10 downto 0) :="00010000000";
constant READFLAG : std_logic_vector(10 downto 0) :="00100000000";
constant WRITERAM : std_logic_vector(10 downto 0) :="01000000000";
constant READRAM : std_logic_vector(10 downto 0) :="10000000000";

constant cur_inc : std_logic :='1';
constant cur_dec : std_logic :='0';
constant cur_shift : std_logic :='1';
constant cur_noshift : std_logic :='0';
constant open_display : std_logic :='1';
constant open_cur : std_logic :='0';
constant blank_cur : std_logic :='0';
constant shift_display : std_logic :='1';
constant shift_cur : std_logic :='0';
constant right_shift : std_logic :='1';
constant left_shift : std_logic :='0';
constant datawidth8 : std_logic :='1';
constant datawidth4 : std_logic :='0';
constant twoline : std_logic :='1';
constant oneline : std_logic :='0';
constant font5x10 : std_logic :='1';
constant font5x7 : std_logic :='0';

signal state : std_logic_vector(10 downto 0);
signal counter : integer range 0 to 127;
signal div_counter : integer range 0 to 15;
signal flag : std_logic;
constant DIVSS : integer :=15;

signal char_addr : std_logic_vector(5 downto 0);
signal data_in : std_logic_vector(7 downto 0);
component char_ram
port( address : in std_logic_vector(5 downto 0) ;
data : out std_logic_vector(7 downto 0)
);
end component;

signal clk_int: std_logic;

signal clkcnt: std_logic_vector(18 downto 0);
constant divcnt: std_logic_vector(18 downto 0):="1111001110001000000";
signal clkdiv: std_logic;
signal tc_clkcnt: std_logic;
begin

process(clk,reset)
begin
if(reset='0')then
clkcnt<="0000000000000000000";
elsif(clk'event and clk='1')then
if(clkcnt=divcnt)then
clkcnt<="0000000000000000000";
else
clkcnt<=clkcnt+1;
end if;
end if;
end process;
tc_clkcnt<='1' when clkcnt=divcnt else
'0';

process(tc_clkcnt,reset)
begin
if(reset='0')then
clkdiv<='0';
elsif(tc_clkcnt'event and tc_clkcnt='1')then
clkdiv<=not clkdiv;
end if;
end process;

clk_out<=clk_int;

process(clkdiv,reset)
begin
if(reset='0')then
clk_int<='0';
elsif(clkdiv'event and clkdiv='1')then
clk_int<= not clk_int;
end if;
end process;

process(clkdiv,reset)
begin
if(reset='0')then
lcd_e<='0';
elsif(clkdiv'event and clkdiv='0')then
lcd_e<= not lcd_e;
end if;
end process;

aa:char_ram
port map( address=>char_addr,data=>data_in);

lcd_rs <= '1' when state =WRITERAM or state = READRAM else '0';
lcd_rw <= '0' when state =CLEAR or state = RETURNCURSOR or state=SETMODE or state=SWITCHMODE or state=SHIFT or state= SETFUNCTION or state=SETCGRAM or state =SETDDRAM or state =WRITERAM else
'1';
data <="00000001" when state =CLEAR else
"00000010" when state =RETURNCURSOR else
"000001"& cur_inc & cur_noshift when state = SETMODE else
"00001" & open_display &open_cur & blank_cur when state =SWITCHMODE else
"0001" & shift_display &left_shift &"00" when state = SHIFT else
"001" & datawidth8 & twoline &font5x10 & "00" when state=SETFUNCTION else
"01000000" when state =SETCGRAM else
"10000000" when state =SETDDRAM and counter =0 else
"11000000" when state =SETDDRAM and counter /=0 else
data_in when state = WRITERAM else
"ZZZZZZZZ";

char_addr <=conv_std_logic_vector( counter,6) when state =WRITERAM and counter<40 else
conv_std_logic_vector( counter-41+8,6) when state= WRITERAM and counter>40 and counter<81-8 else
conv_std_logic_vector( counter-81+8,6) when state= WRITERAM and counter>81-8 and counter<81 else
"000000";



process(clk_int,Reset)
begin
if(Reset='0')then
state<=IDLE;
counter<=0;
flag<='0';
div_counter<=0;
elsif(clk_int'event and clk_int='1')then
case state is
when IDLE =>
if(flag='0')then
state<=SETFUNCTION;
flag<='1';
counter<=0;
div_counter<=0;
else
if(div_counterdiv_counter<=div_counter +1;
state<=IDLE;
else
div_counter<=0;
state <=SHIFT;
end if;
end if;
when CLEAR =>
state<=SETMODE;
when SETMODE =>
state<=WRITERAM;
when RETURNCURSOR =>
state<=WRITERAM;
when SWITCHMODE =>
state<=CLEAR;
when SHIFT =>
state<=IDLE;
when SETFUNCTION =>
state<=SWITCHMODE;
when SETCGRAM =>
state<=IDLE;
when SETDDRAM =>
state<=WRITERAM;
when READFLAG =>
state<=IDLE;
when WRITERAM =>
if(counter =40)then
state<=SETDDRAM;
counter<=counter+1;
elsif(counter/=40 and counter<81)then
state<=WRITERAM;
counter<=counter+1;
else
state<=SHIFT;
end if;
when READRAM =>
state<=IDLE;
when others =>
state<=IDLE;
end case;
end if;
end process;

end Behavioral;







文件2代码 char_ram：
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;

entity char_ram is
port( address : in std_logic_vector(5 downto 0) ;
data : out std_logic_vector(7 downto 0)
);
end char_ram;

architecture fun of char_ram is

function char_to_integer ( indata :character) return integer is
variable result : integer range 0 to 16#7F#;
begin
case indata is
when ' ' => result := 32;
when '!' => result := 33;
when '"' => result := 34;
when '//m.amcfsurvey.com/forum/thread/221637/#' => result := 35;
when '$' => result := 36;
when '%' => result := 37;
when '&' => result := 38;
when ''' => result := 39;
when '(' => result := 40;
when ')' => result := 41;
when '*' => result := 42;
when '+' => result := 43;
when ',' => result := 44;
when '-' => result := 45;
when '.' => result := 46;
when '/' => result := 47;
when '0' => result := 48;
when '1' => result := 49;
when '2' => result := 50;
when '3' => result := 51;
when '4' => result := 52;
when '5' => result := 53;
when '6' => result := 54;
when '7' => result := 55;
when '8' => result := 56;
when '9' => result := 57;
when ':' => result := 58;
when ';' => result := 59;
when '<' => result := 60;
when '=' => result := 61;
when '>' => result := 62;
when '?' => result := 63;
when'@'=> result := 64;
when 'A' => result := 65;
when 'B' => result := 66;
when 'C' => result := 67;
when 'D' => result := 68;
when 'E' => result := 69;
when 'F' => result := 70;
when 'G' => result := 71;
when 'H' => result := 72;
when 'I' => result := 73;
when 'J' => result := 74;
when 'K' => result := 75;
when 'L' => result := 76;
when 'M' => result := 77;
when 'N' => result := 78;
when 'O' => result := 79;
when 'P' => result := 80;
when 'Q' => result := 81;
when 'R' => result := 82;
when 'S' => result := 83;
when 'T' => result := 84;
when 'U' => result := 85;
when 'V' => result := 86;
when 'W' => result := 87;
when 'X' => result := 88;
when 'Y' => result := 89;
when 'Z' => result := 90;
when '[' => result := 91;
when '\' => result := 92;
when ']' => result := 93;
when '^' => result := 94;
when '_' => result := 95;
when '`' => result := 96;
when 'a' => result := 97;
when 'b' => result := 98;
when 'c' => result := 99;
when 'd' => result := 100;
when 'e' => result := 101;
when 'f' => result := 102;
when 'g' => result := 103;
when 'h' => result := 104;
when 'i' => result := 105;
when 'j' => result := 106;
when 'k' => result := 107;
when 'l' => result := 108;
when 'm' => result := 109;
when 'n' => result := 110;
when 'o' => result := 111;
when 'p' => result := 112;
when 'q' => result := 113;
when 'r' => result := 114;
when 's' => result := 115;
when 't' => result := 116;
when 'u' => result := 117;
when 'v' => result := 118;
when 'w' => result := 119;
when 'x' => result := 120;
when 'y' => result := 121;
when 'z' => result := 122;
when '{' => result := 123;
when '|' => result := 124;
when '}' => result := 125;
when '~' => result := 126;
when others => result :=32;
end case;
return result;
end function;

begin
process (address)
begin
case address is
when "000000" =>data<=conv_std_logic_vector(char_to_integer ('W') ,8);
when "000001" =>data<=conv_std_logic_vector(char_to_integer ('e') ,8);
when "000010" =>data<=conv_std_logic_vector(char_to_integer ('l') ,8);
when "000011" =>data<=conv_std_logic_vector(char_to_integer ('e') ,8);
when "000100" =>data<=conv_std_logic_vector(char_to_integer ('c') ,8);
when "000101" =>data<=conv_std_logic_vector(char_to_integer ('o') ,8);
when "000110" =>data<=conv_std_logic_vector(char_to_integer ('m') ,8);
when "000111" =>data<=conv_std_logic_vector(char_to_integer ('e') ,8);
when "001000" =>data<=conv_std_logic_vector(char_to_integer (' ') ,8);
when "001001" =>data<=conv_std_logic_vector(char_to_integer (' ') ,8);
when "001010" =>data<=conv_std_logic_vector(char_to_integer ('B') ,8);
when "001011" =>data<=conv_std_logic_vector(char_to_integer ('A') ,8);
when "001100" =>data<=conv_std_logic_vector(char_to_integer ('I') ,8);
when "001101" =>data<=conv_std_logic_vector(char_to_integer ('X') ,8);
when "001110" =>data<=conv_std_logic_vector(char_to_integer ('U') ,8);
when "001111" =>data<=conv_std_logic_vector(char_to_integer ('N') ,8);
when "010000" =>data<=conv_std_logic_vector(char_to_integer (' ') ,8);
when "010001" =>data<=conv_std_logic_vector(char_to_integer (' ') ,8);
when "010010" =>data<=conv_std_logic_vector(char_to_integer ('B') ,8);
when "010011" =>data<=conv_std_logic_vector(char_to_integer ('o') ,8);
when "010100" =>data<=conv_std_logic_vector(char_to_integer ('a') ,8);
when "010101" =>data<=conv_std_logic_vector(char_to_integer ('r') ,8);
when "010110" =>data<=conv_std_logic_vector(char_to_integer ('d') ,8);
when "010111" =>data<=conv_std_logic_vector(char_to_integer ('!') ,8);
when others =>data<=conv_std_logic_vector(char_to_integer (' ') ,8);
end case;
end process;
end fun;