VGA controller VHDL code

library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.STD_LOGIC_ARITH.ALL; use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity Vga is

   Port ( clk_i : in  STD_LOGIC;
          sw_i  : in  STD_LOGIC_VECTOR (15 downto 0); -- (11 downto 8) is RED, (7 downto 4) is GREEN, (3 downto 0) is BLUE
                                                      -- Writing directly to RAM and from RAM to VGA interface.
                                                      -- Writing when sw_i(15) is high
          -- VGA Output Signals
          vga_hs_o : out  STD_LOGIC; -- Horizontal sync puls to VGA interface
          vga_vs_o : out  STD_LOGIC; -- Vertical sync puls to VGA interface
          vga_red_o    : out  STD_LOGIC_VECTOR (3 downto 0); -- Red to VGA interface
          vga_green_o  : out  STD_LOGIC_VECTOR (3 downto 0); -- Green to VGA interface
          vga_blue_o   : out  STD_LOGIC_VECTOR (3 downto 0) -- Blue to VGA interface
          );

end Vga;

architecture Behavioral of Vga is

-- Component Declarations

-- 25.2MHz Clock COMPONENT clk_wiz_25_2MHz PORT (

     clk_in_100MHz:  in STD_LOGIC;
     clk_out_25_2: out STD_LOGIC;
     reset         : in STD_LOGIC;
     locked        : out STD_LOGIC 
     );

END COMPONENT;

-- Ram block for pixels COMPONENT PIX_RAM

 PORT (
   clka : IN STD_LOGIC;
   ena : IN STD_LOGIC;
   wea : IN STD_LOGIC_VECTOR(0 DOWNTO 0);
   addra : IN STD_LOGIC_VECTOR(18 DOWNTO 0);
   dina : IN STD_LOGIC_VECTOR(11 DOWNTO 0);
   douta : OUT STD_LOGIC_VECTOR(11 DOWNTO 0)
 );

END COMPONENT;

-- Constants for VGA Resolutions

640x480 60Hz-------

constant WIDTH : natural := 640; constant HEIGHT : natural := 480;

constant H_FP : natural := 16; --H front porch width (pixels) constant H_PW : natural := 96; --H sync pulse width (pixels) constant H_TOT : natural := 800; --H total period (pixels)

constant V_FP : natural := 10; --V front porch width (lines) constant V_PW : natural := 2; --V sync pulse width (lines) constant V_TOT : natural := 525; --V total period (lines)

-- VGA signals: Counters, Sync, Red, Gree, Blue

-- Activates the screen when it is in the frame area signal SCREEN_ON : std_logic;

-- Horizontal and Vertical counters signal h_count : std_logic_vector(11 downto 0) := (others =>'0'); signal v_count : std_logic_vector(11 downto 0) := (others =>'0');

-- signal for the VGA interface signal vga_red : std_logic_vector(3 downto 0); signal vga_blue : std_logic_vector(3 downto 0); signal vga_green : std_logic_vector(3 downto 0);

-- CLOCK signals

signal pxl_clk: std_logic; -- pxl_clk is 25.2MHz signal reset: std_logic := '0';

-- RAM signals

signal data_out : std_logic_vector(11 downto 0) := (others =>'0'); signal data_inn : std_logic_vector(11 downto 0) := (others =>'0'); signal address : std_logic_vector(18 downto 0) := (others =>'0'); signal write : std_logic_vector(0 downto 0) ;

begin

---------------------------
-- PORT MAPS
--------------------------- 

-- PIXELGENERATOR - pxl_clk=25.2MHz
PIXELGENERATOR : clk_wiz_25_2MHz PORT MAP
    (--clock inn
     clk_in_100MHz  => clk_i,
     --clock out
     clk_out_25_2 => pxl_clk,
     --reset active high
     reset          => reset,
     --status and controll signals
     locked         => open
    );
    
-- RAM
     RAM : PIX_RAM PORT MAP
         (
          clka  => clk_i,
          ena  => '1',
          wea  => write,
          addra  => address,
          dina  => data_inn,
          douta  => data_out
         );

-- Generate Horizontal, Vertical counters and the Sync signals

 -- Horizontal counter
 process (pxl_clk)
 begin
   if (rising_edge(pxl_clk)) then
     if (h_count = (H_TOT - 1)) then
       h_count <= (others =>'0');
     else
       h_count <= h_count + 1;
     end if;
   end if;
 end process;
 
 -- Vertical counter
 process (pxl_clk)
 begin
   if (rising_edge(pxl_clk)) then
     if ((h_count = (H_TOT - 1)) and (v_count = (V_TOT - 1))) then
       v_count <= (others =>'0');
     elsif (h_count = (H_TOT - 1)) then
       v_count <= v_count + 1;
     end if;
   end if;
 end process;
   
 -- Horizontal sync
 process (pxl_clk)
 begin
   if (rising_edge(pxl_clk)) then
     if (h_count >= (H_FP + WIDTH - 1)) and (h_count < (H_FP + WIDTH + H_PW - 1)) then
       vga_hs_o <= '1';
     else
       vga_hs_o <= '0';
     end if;
   end if;
 end process;
 
 -- Vertical sync
 process (pxl_clk)
 begin
   if (rising_edge(pxl_clk)) then
     if (v_count >= (V_FP + HEIGHT - 1)) and (v_count < (V_FP + HEIGHT + V_PW - 1)) then
       vga_vs_o <= '1';
     else
       vga_vs_o <= '0';
     end if;
   end if;
 end process;

-- RAM interface

-- Synchronizing reading and writing of adresses with the VGA interface

 process (pxl_clk)
 begin
   if (rising_edge(pxl_clk)) then
     if h_count < WIDTH and v_count < HEIGHT then
       address <= address + 1;
     else
       address <= (others =>'0');
     end if;
   end if;
 end process;

-- SCREEN ON

-- screening signal
SCREEN_ON <= '1' when h_count < WIDTH and v_count < HEIGHT
          else '0';

-- Turn Off VGA RBG Signals if outside of the active screen -- Make a 4-bit AND logic with the R, G and B signals

vga_red_o <= (SCREEN_ON & SCREEN_ON & SCREEN_ON & SCREEN_ON) and vga_red;
vga_green_o <= (SCREEN_ON & SCREEN_ON & SCREEN_ON & SCREEN_ON) and vga_green;
vga_blue_o <= (SCREEN_ON & SCREEN_ON & SCREEN_ON & SCREEN_ON) and vga_blue;


--------------------
-- Rerouting signals
--------------------
vga_red   <= data_out(11 downto 8);
vga_green <= data_out(7 downto 4);
vga_blue  <= data_out(3 downto 0);

data_inn <= sw_i(11 downto 0); -- (11 downto 8) is RED, (7 downto 4) is GREEN, (3 downto 0) is BLUE
write <= sw_i(15 downto 15); -- Activ high when writing to BRAM

end Behavioral;