em swioports.vhd

RatioMode       : inout std_logic_vector(  2 downto 0 );            -- Pixel Ratio 1:1 for VGA Output (default is 0) (toggle 0-7) (60Hz only)

 -- in assignment: 'Port $41 ID212 [Smart Commands]' (write only)
                if( req = '1' and wrt = '1' and (adr(3 downto 0) = "0001")  and (io40_n = "00101011") )then
                    io41_id212_n    <=  not dbo;
                    case dbo is
                        -- SMART CODE   #000
--                      when "00000000" =>                                  -- 0x00 Null Command (Reserved)
--                          null;

                        when "01111111" =>                                  -- 0x7f Pixel Ratio Toggle for VGA output
                            RatioMode       <=  RatioMode - 1;

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em vdp_vga.vhd linha 186

 -- PIXEL RATIO 1:1 (NTSC MODE ONLY)
    PROCESS( CLK21M )
    BEGIN
        IF( CLK21M'EVENT AND CLK21M = '1' )THEN
            IF( PALMODE = '1' )THEN
                DISP_START_X <= "00001010111";                  -- 88  = CENTER (PAL MODE)
            ELSIF( PALMODE = '0' AND RATIOMODE = "000" )THEN
                DISP_START_X <= "00001000111";                  -- 71  = CENTER (NTSC MODE)
            ELSIF( VCOUNTERIN < 56 )THEN
              IF( VCOUNTERIN(0) = '0' )THEN
                  CASE RATIOMODE IS
                  WHEN "111" => DISP_START_X <= "00000100011";  -- 35  = LEFT -3
                  WHEN "110" => DISP_START_X <= "00000100100";  -- 36  = LEFT -2
                  WHEN "101" => DISP_START_X <= "00000100101";  -- 37  = LEFT -1
                  WHEN "100" => DISP_START_X <= "00000100110";  -- 38  = LEFT   (NTSC MODE) (CENTER - 33)
                  WHEN "011" => DISP_START_X <= "00000100111";  -- 39  = LEFT +1
                  WHEN "010" => DISP_START_X <= "00000101000";  -- 40  = LEFT +2
                  WHEN "001" => DISP_START_X <= "00000101001";  -- 41  = LEFT +3
                  WHEN OTHERS => NULL;
                  END CASE;
              ELSE
                  DISP_START_X <= "00001101010";                -- 106 = RIGHT  (NTSC MODE) (684 - 576 - 2)
              END IF;
            ELSE
                DISP_START_X <= "00001000111";                  -- 71  = CENTER (NTSC MODE) (RIGHT - 35)
            END IF;
        END IF;
    END PROCESS;