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-- LCD 2 lines controller
--
-- 8 bits interface --
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-- ESIEE
-- Creation : A. Exertier, mars 2008
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library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
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-- INPUTS
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-- clk : system clock
-- resetn : aynchronous active low reset
-- en_250kHz : enable at 250 kHz (lasts 1 clock cycle)
-- char : input ASCII character
-- write_char : write character command
-- ready : set to 1 when device is ready for a writing
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-- OUTPUTS
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-- LCD_DATA : ASCII data to LCD
-- LCD_RS : RS to LCD
-- LCD_RW : Read/write to LCD
-- LCD_EN : Enable to LCD
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Entity LCD_controller is
port(
clk : in std_logic;
resetn : in std_logic;
en_250kHz : in std_logic;
mode : in std_logic_vector(1 downto 0);
char : in std_logic_vector (7 downto 0);
address : in std_logic_vector(6 downto 0);
write_char : in std_logic;
write_address : in std_logic;
ready : out std_logic;
D : in std_logic;
C : in std_logic;
B : in std_logic;
-- LCD signals
LCD_data : inout std_logic_vector(7 downto 0);
LCD_RS : out std_logic;
LCD_RW : out std_logic;
LCD_EN : out std_logic
);
end LCD_Controller;
Architecture RTL of LCD_Controller is
type State_type is (Boot, FunctionSet, DisplayControl, EntryModeSet, Clear,
Address_set, Waiting, Verify, Putchar, Homecursor,
WriteAddress, WriteData);
signal present : State_type;
signal future : State_type;
-- Timing Constants :
constant T_30ms : integer := 30_000/4; -- 7500; -- 30 ms
constant T_2ms : integer := 2_000/4; --500; -- 2 ms
constant T_40us : integer := 12; -- > 39 us after E down
constant En_delay : integer := 1; -- 8 us
constant LastPosition : integer := 16;
-- CLEAR DisplayControl
constant CLR : std_logic_vector(7 downto 0) := "00000001";
-- RETURN HOME
constant RET_HOME : std_logic_vector(7 downto 0) := "00000010"; -- 0000001x
-- DDRAM address to 0 (beginning of first line)
-- ENTRY MODE SET
constant ENTRY_MODE : std_logic_vector(7 downto 0) := "00000110"; -- 0000 01 I/D S
-- I/D : 1 => Increment, 0 => Decrement
-- S : 1 => DisplayControl shift
-- FUNCTION SET
constant FUNC_SET : std_logic_vector(7 downto 0) := "00111100"; -- 001 DL N F xx
-- DL : 1 => 8 bits, 0 => 4 bits
-- N : 1 => 2 lines, 0 => 1 line
-- F : 1 => 5x10 dots, 0 => 5x8 dots
-- DisplayControl ON/OFF CONTROL
constant DON : std_logic_vector(7 downto 0) := "00001110"; -- 0000 1 D C B
-- D : 1 => Display on
-- C : 1 => Cursor on
-- B : 1 => Cursor blink on
constant RET_LINE2 : std_logic_vector(7 downto 0) := "11000000";
-- set DDRAM address to 32 (beginning of second line)
constant RET_LINE1 : std_logic_vector(7 downto 0) := "10000000";
-- set DDRAM address to 0 (beginning of first line)
signal Position : natural range 0 to 2*LastPosition;
signal Count : natural range 0 to T_30ms;
signal inc_C : std_logic;
signal cmd_P : std_logic_vector(1 downto 0);
--signal reset_P : std_logic;
signal test_EN : std_logic;
signal test_T_40us : std_logic;
begin
LCD_RW <= '0';
process (Clk, resetn)
begin
if resetn = '0' then
present <= Boot;
position <= 0;
count <= 0;
elsif rising_edge(clk) then
if en_250kHz = '1' then
present <= future;
if inc_C = '1' then count <= count+1;
else count <= 0;
end if;
case cmd_P is
when "00" => position <= 0;
when "01" => if position >= 31 then position <= 0;
else position <= position+1;
end if;
when "10" => if address(6 downto 4) = "000" then position <= to_integer(unsigned(address(3 downto 0)));
elsif address(6 downto 4) = "100" then position <= to_integer(unsigned(address(3 downto 0)))+16;
else position <= 0;
end if;
when others => null;
end case;
end if;
end if;
end process;
test_EN <= '1' when Count = En_delay else '0';
test_T_40us <= '1' when count >= T_40us else '0';
process(present, Write_char, mode, write_address, count, Position,char,
address,test_EN, test_T_40us , D, C, b) is
begin
future <= present;
inc_C <= '1';
cmd_P <= "11";
ready <= '0';
LCD_RS <= '0';
LCD_EN <= '0';
LCD_data <= X"00";
case present is
when Boot => -- Wait for 30 ms
if Count = T_30ms then
future <= FunctionSet;
inc_C <= '0';
end if;
cmd_P <= "00";
when FunctionSet => -- Function Set
LCD_data <= FUNC_SET;
LCD_EN <= test_EN;
if test_T_40us = '1' then
future <= EntryModeSet;
inc_C <= '0';
end if;
cmd_P <= "00";
when EntryModeSet => -- Entry Mode Set
LCD_data <= ENTRY_MODE;
LCD_EN <= test_EN;
if test_T_40us = '1' then
future <= DisplayControl;
inc_C <= '0';
end if;
cmd_P <= "00";
when DisplayControl =>
-- Display ON/OFF control
LCD_data <= DON(7 downto 3)&D&C&B;
LCD_EN <= test_EN;
if test_T_40us = '1' then
future <= Clear;
inc_C <= '0';
end if;
cmd_P <= "00";
when Clear =>
-- Clear Display
LCD_data <= CLR;
LCD_EN <= test_EN;
if Count >= T_2ms then
inc_C <= '0';
future <= Address_set;
end if;
cmd_P <= "00";
when Address_set =>
-- DDRAM address set
LCD_data <= RET_LINE1;
LCD_EN <= test_EN;
if test_T_40us = '1' then
future <= Waiting;
inc_C <= '0';
end if;
cmd_P <= "00";
when Waiting =>
-- Waits for input
if mode (1) = '1' then
if write_address = '1' then future <= WriteAddress;
elsif write_char = '1' then future <= WriteData;
end if;
elsif write_char = '1' then
if char = x"0C" then future <= Clear;
else future <= Putchar;
end if;
end if;
ready <= '1';
inc_C <= '0';
when WriteAddress =>
-- Set CGRAM/DDRAM Address
if mode(0) = '0' then LCD_data <= '1'&address;
else LCD_data <= "01"&address(5 downto 0);
end if;
LCD_EN <= test_EN;
if test_T_40us = '1' then
future <= Waiting;
inc_C <= '0';
end if;
cmd_P <= "10";
when WriteData =>
-- Write data to CGRAM or DDRAM
LCD_RS <= '1';
LCD_EN <= test_EN;
LCD_DATA <= char;
if test_T_40us = '1' then
future <= Waiting;
inc_C <= '0';
cmd_P <= "01";
end if;
when Verify =>
if char = x"0C" then -- FormFeed => Clear Screen
future <= Clear;
else future <= Putchar;
end if;
inc_C <= '0';
LCD_data <= char;
when Putchar =>
-- Display character on the LCD
LCD_RS <= '1';
LCD_EN <= test_EN;
if test_T_40us = '1' then
if Position = 15 or Position = 31 then
future <= HomeCursor;
else future <= Waiting;
cmd_P <= "01";
end if;
inc_C <= '0';
end if;
LCD_data <= char;
when HomeCursor =>
LCD_EN <= test_EN;
if Position = 31 then LCD_data <= RET_LINE1; --RET_HOME;
else LCD_data <= RET_LINE2;
end if;
if test_T_40us = '1' then
--if Count >= T_2ms then
if Position = 31 then cmd_P <= "00";
else cmd_P <= "01";
end if;
future <= Waiting;
inc_C <= '0';
end if;
end case;
end process;
end RTL;