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--利用FPGA驱动LCD显示中文字符"年"的VHDL程序。
--文件名 ：lcd1602.vhd。
--功能 ： FGAD驱动LCD显示中文字符"年"。
--最后修改日期 ：2006.08.28。

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity LCD1602 is
Port ( Clk : in std_logic; --状态机时钟信号，同时也是液晶时钟信号，其周期应该满足液晶数据的建立时间
Reset:in std_logic;
LCD_RS : out std_logic; --寄存器选择信号
LCD_RW : out std_logic; --液晶读写信号
LCD_EN : out std_logic; --液晶时钟信号
LED : out std_logic;
LCD_Data : out std_logic_vector(7 downto 0)); --液晶数据信号
end LCD1602;

architecture Behavioral of LCD1602 is
type state is (set_dlnf,set_cursor,set_dcb,set_cgram,write_cgram,set_ddram,write_LCD_Data);
signal Current_State:state;
type ram2 is array(0 to 7) of std_logic_vector(7 downto 0);
constant cgram:ram2:=(
("00001000"),
("00001111"),
("00010010"),
("00001111"),
("00001010"),
("00011111"),
("00000010"),
("00000010"));--年字符数据存储器
signal Clkk : std_logic;
signal Count : std_logic_vector(20 downto 0);
signal Clk_Out : std_logic;
signal LCD_Clk : std_logic;
begin
LCD_EN <= Clk_Out ; --液晶时钟信号
LED <= Clk_Out;
LCD_RW <= '0' ; --写数据
clock :
process(Clk,Reset)
begin
if(Reset = '0')then
Count <= (others => '0');
elsif(rising_edge(clk))then
Count <= Count + 1;
if(Count = 0)then
Clk_Out <= not Clk_Out;
end if;
end if;
LCD_Clk <= Clk_Out;
end process;
control:
process(LCD_Clk,Reset,Current_State) --液晶驱动控制器
variable cnt1: std_logic_vector(2 downto 0);
begin
if Reset='0'then
Current_State<=set_dlnf;
cnt1:=(others => '1');
LCD_RS<='0';
elsif rising_edge(LCD_Clk)then
Current_State <= Current_State ;
LCD_RS <= '0';
case Current_State is
when set_dlnf=>
LCD_Data<="00111100";--3cH
Current_State<=set_cursor;
when set_cursor=>
LCD_Data<="00000110";--06H
Current_State<=set_dcb;
when set_dcb=>
LCD_Data<="00001111";--0fH
Current_State<=set_cgram;
when set_cgram=>
LCD_Data<="01000000";--40H
Current_State<=write_cgram;
when write_cgram=> --向CGRAM中写入"年"
LCD_RS<='1';
cnt1:=cnt1+1;
LCD_Data<=cgram(conv_integer(cnt1));
if cnt1 = "111" then
Current_State<=set_ddram;
end if;
when set_ddram=> --从第一行的起始地址开始显示
LCD_Data<="10000000";--80H
Current_State<=write_LCD_Data;
when write_LCD_Data=>
LCD_RS<='1';
LCD_Data<="00000000"; --写入字符"年"
when others => null;
end case;
end if;
end process;
end Behavioral;