VGA szinkron idők CPLD-ből

[Horváth Vilmos]

VGA kimenetet szeretnék csinálni.
A netten találtam egy forrást, ami ugyan működik de vízszintes 
visszafutások látszanak.
Le tudná valaki írni mikor is kell és mennyi ideig kiadni a szinkron 
jeleket.

Csatoltam a forrást hátha valaki...


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


entity demo is
    Port ( 
	clk : in std_logic;
	hsync, vsync : out std_logic;
	rgb : out std_logic_vector(2 downto 0);
end demo;

architecture Behavioral of demo is

--  VGA

subtype counter is integer range 0 to 1023;
subtype nibble is integer range 0 to 15;
-- constants for the timing of one scan line (# of dot clock cycles)
constant hsync_start : counter := 0;
constant hsync_end : counter := 94;
constant hscan_start : counter := 139;
constant hscan_end : counter := 780;
constant hline_end : counter := 800;

-- constants for the timing of one field (# of scan lines)
constant vsync_start : counter := 0;
constant vsync_end : counter := 1;
constant vscan_start : counter := 34;
constant vscan_end : counter := 514;
constant field_end : counter := 524;

-- global signals
signal dot_count, row_count : counter;

signal	vgaclk: std_logic;

begin



-- VGA
	with dot_count select
        hsync <= '1' when hsync_start to hsync_end,
        '0' when others;

    	with row_count select
        vsync <= '1' when vsync_start to vsync_end,
        '0' when others;


vgascan : process
begin
        wait until rising_edge(clk);

        -- compute waveform counter state
        if dot_count < hline_end then
            dot_count <= dot_count + 1;
        else
            dot_count <= 0;
            if row_count < field_end then
                row_count <= row_count + 1;
            else
                row_count <= 0;
            end if;
        end if;

        -- compute rgb outputs
        if dot_count > hscan_start and dot_count < hscan_end then
             rgb <= "100";
        else
            rgb <= "000";
        end if;

    end process vgascan;

end Behavioral;