VGA problem with timing

Discussion in 'VHDL' started by stepi, May 3, 2011.

  1. stepi

    stepi

    Joined:
    May 3, 2011
    Messages:
    3
    HI
    I found timing in datasheet and use it, there was some mistake so I repaired it. But when I done and run the program. Monitor showed just blank screen and no information (resolution or no connect). I used 640x480 60Hz (horizontal 96+48+640+16=800pix, vertical 2+33+480+10=525l).
    Here is my code. In other part R=G=B=x"3FF" and vga_clk=(clock_50)/2
    Code (Text):

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

    entity generaterow is
        port ( clk: in std_logic;
                blank: out std_logic:='0';
                hs,vs,sync: out std_logic:='1';
                endrow: buffer std_logic );
    end generaterow;

    architecture mujgeneraterow of generaterow is
    signal drawrow:std_logic:='1';
    begin  
        row:process(clk)
        variable arow,brow,crow,drow,ukazatelrow,ukazatelframe,aframe,cframe,dframe:integer:=0;
        variable bframe:integer:=-1;
        variable jakyradek:integer:=0;
        begin
        if rising_edge(clk) and drawrow='1' then
            if ukazatelrow=0 then       --back porch ROW
                brow:=brow+1;
                if brow=44 then
                    brow:=0;
                    ukazatelrow:=1;
                    BLANK<='1';
                end if;
            elsif ukazatelrow=1 then        --displey interval ROW
                crow:=crow+1;
                if crow=640 then
                    crow:=0;
                    ukazatelrow:=2;
                    BLANK<='0';
                end if;
            elsif ukazatelrow=2 then        --front porch ROW
                drow:=drow+1;
                if drow=20 then
                    drow:=0;
                    ukazatelrow:=3;
                    --BLANK<='1';
                    HS<='0';
                    SYNC<='0';
                end if;
            elsif ukazatelrow=3 then    --synchronizace ROW
                arow:=arow+1;
                if arow=96 then
                    arow:=0;
                    ukazatelrow:=0;
                    --BLANK<='0';
                    HS<='1';
                    SYNC<='1';
                    jakyradek:=jakyradek+1;
                end if;
                if jakyradek=480 then
                    endrow<=not endrow;
                    jakyradek:=0;
                    drawrow<='0';
                end if;
            end if;
        elsif rising_edge(clk) and drawrow='0' then    
            if ukazatelframe=0 then              --back porch frame
                bframe:=bframe+1;
                if bframe=26400 then
                    bframe:=0;
                    drawrow<='1';
                    ukazatelframe:=1;
                end if;
            elsif ukazatelframe=1 then            --front porch frame
                dframe:=dframe+1;
                if dframe=8000 hen                 
                    dframe:=0;
                    ukazatelframe:=2;
                    --blank<='1';
                    sync<='0';
                    vs<='0';
                end if;
            elsif ukazatelframe=2 then                  --synchro frame
                aframe:=aframe+1;
                if aframe=800 then
                    aframe:=0;
                    ukazatelframe:=0;
                    --blank<='0';
                    sync<='1';
                    vs<='1';
                end if;
            end if;
        end if;
        end process;
       
    end mujgeneraterow;
     
    Have you got idea why monitor show just blank screen instead of white screen.
    Thank you for help, comment or idea.
    Martin Stepanek
     
    stepi, May 3, 2011
    #1
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