library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity chardisplay is
Port ( clk : in STD_LOGIC;
reset : in STD_LOGIC;
data : out STD_LOGIC_VECTOR (7 downto 0);
en : out STD_LOGIC;
rs : out STD_LOGIC);
end chardisplay;
architecture Behavioral of chardisplay is
type msg_array is array (0 to 12) of std_logic_vector(7 downto 0); -- Increase
size for 13 characters
constant msg : msg_array := (
"00100000", -- Space (ASCII 32)
"01010111", -- W (ASCII 87)
"01000101", -- E (ASCII 69)
"01001100", -- L (ASCII 76)
"01000011", -- C (ASCII 67)
"01001111", -- O (ASCII 79)
"01001101", -- M (ASCII 77)
"01000101", -- E (ASCII 69)
"00100000", -- Space (ASCII 32)
"01001001", -- I (ASCII 73)
"00110010", -- 2 (ASCII 50)
"01001001", -- I (ASCII 73)
"01010100" -- T (ASCII 84)
);
signal state : integer := 0; -- State machine state
signal index : integer := 0; -- Index for the message
signal counter : integer := 0; -- Counter for timing
constant clk_div : integer := 12000; -- For a 1 ms delay at 12 MHz
begin
process(clk, reset)
begin
if reset = '1' then
state <= 0;
index <= 0;
data <= (others => '0'); -- Default value for data
en <= '0'; -- Default value for enable
rs <= '0'; -- Default value for register select
counter <= 0;
elsif rising_edge(clk) then
case state is
when 0 =>
rs <= '0'; -- Instruction mode
data <= "00111000"; -- Function set: 8-bit mode, 2
lines, 5x8 dots
en <= '1'; -- Enable signal high for
initialization
state <= 1;
when 1 =>
en <= '0'; -- Disable enable after the
command
counter <= counter + 1;
if counter >= clk_div then
counter <= 0;
rs <= '0'; -- Instruction mode
data <= "00001100"; -- Display ON, cursor OFF
en <= '1'; -- Enable signal high for next
command
state <= 2;
end if;
when 2 =>
en <= '0'; -- Disable enable after the
command
counter <= counter + 1;
if counter >= clk_div then
counter <= 0;
rs <= '0'; -- Instruction mode
data <= "00000001"; -- Clear display
en <= '1'; -- Enable signal high for clear
command
state <= 3;
end if;
when 3 =>
en <= '0'; -- Disable enable after the
command
counter <= counter + 1;
if counter >= clk_div then
counter <= 0;
if index < 13 then -- For " WELCOME I2IT" (13
characters with leading space)
rs <= '1'; -- Data mode
data <= msg(index); -- Send character from the
message array
en <= '1'; -- Enable signal high for
character data
index <= index + 1;
else
state <= 4; -- Finished displaying message
end if;
end if;
when 4 =>
en <= '0'; -- Stay in this state to do
nothing
when others =>
state <= 0; -- Default case
end case;
end if;
end process;
end Behavioral;
