terminal/vga.vhd

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.numeric_std.all;

entity vga is
    port(
        clk: in std_logic;

        x, y: out std_logic_vector(9 downto 0);
        pixel_rgb: in std_logic_vector(23 downto 0);

        dvi_d: out std_logic_vector(11 downto 0);
        dvi_clk: out std_logic;
        dvi_hsync: out std_logic;
        dvi_vsync: out std_logic;
        dvi_de: out std_logic
    );
end vga;

architecture behavioral of vga is
    signal second_batch: std_logic := '0';
    signal hcount: std_logic_vector(9 downto 0) := (others => '0');
    signal vcount: std_logic_vector(9 downto 0) := (others => '0');
    signal data_enabled: std_logic;
begin
    dvi_clk <= clk;
    --dvi_clk <= second_batch;
    dvi_de <= data_enabled;

    data_enabled <= '1' when hcount < 640 and vcount < 480 else
                    '0';
    
    dvi_hsync <= '0' when 656 <= hcount and hcount <= 720 else
                 '1';
    dvi_vsync <= '0' when 483 <= vcount and vcount <= 487 else
                 '1';
    
    x <= hcount when data_enabled = '1' and hcount < 640 else std_logic_vector(to_unsigned(639, 10));
    y <= vcount when data_enabled = '1' and vcount < 480 else std_logic_vector(to_unsigned(479, 10));
    
    data_output: process(clk)
    begin
        if rising_edge(clk) then
            if data_enabled = '1' then
                if second_batch = '0' then
                    dvi_d <= pixel_rgb(11 downto 0);
                else
                    dvi_d <= pixel_rgb(23 downto 12);
                end if;
            else
                dvi_d <= (others => '0');
            end if;

            second_batch <= not second_batch;
        end if;
    end process data_output;

    hcounter: process(clk)
    begin
        if rising_edge(clk) and second_batch = '1' then
            if hcount < 799 then
                hcount <= hcount + 1;
            else
                hcount <= (others => '0');
            end if;
        end if;
    end process hcounter;

    vcounter: process(clk, hcount)
    begin
        if rising_edge(clk) and second_batch = '1' and hcount = 700 then
            if vcount < 499 then
                vcount <= vcount + 1;
            else
                vcount <= (others => '0');
            end if;
        end if;
    end process vcounter;
end behavioral;