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VGA Port

VGA Port. Discussion D5.2. Raster Scan Displays. Electron beam. CRT. Raster Scan Characters. 14. 9. T. 54. H. 48. Character. 45. E. generator. Character line 1. Row. (40 words or. select. 80 bytes). 1 1 1 1 1 0 0 0. Video. Shift register. signal. Character line 2.

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VGA Port

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  1. VGA Port Discussion D5.2

  2. Raster Scan Displays Electron beam CRT

  3. Raster Scan Characters 14 9

  4. T 54 H 48 Character 45 E generator Character line 1 Row (40 words or select 80 bytes) 1 1 1 1 1 0 0 0 Video Shift register signal Character line 2 (40 words or 80 bytes) even addresses odd addresses

  5. Attribute Byte 7 6 5 4 3 2 1 0 BL R G B I R G B Blinking bit Foreground 0 = not blinking 1 = foreground Intensity bit blinking 0 = normal intensity 1 = high intensity Background

  6. Back porch Back porch Front porch

  7. Horizontal Timing 784 144 Pixel clock = 25 MHz Pixel time = 0.04 ms Horizontal video = 640 pixels x 0.04 ms = 25.60 ms Back porch, BP = 16 pixels x 0.04 ms = 0.64 ms Front porch, FP = 16 pixels x 0.04 ms = 0.64 ms Sync pulse, SP = 128 pixels x 0.04 ms = 5.12.ms Horizontal Scan Lines = SP + BP + HV + FP = 128 + 16 + 640 + 16 = 800 pixels x 0.04 ms = 32 ms 1/60 Hz = 16.67 ms / 32 ms = 521 horizontal scan lines per frame

  8. Vertical Timing 511 31 Pixel clock = 25 MHz Horizontal scan time = 32 ms Vertical video = 480 lines x 32 ms = 15.360 ms Back porch, BP = 29 lines x 32 ms = 0.928 ms Front porch, FP = 10 lines x 32 ms = 0.320 ms Sync pulse, SP = 2 lines x 32 ms = 0.064 ms Vertical Scan Lines = SP + BP + VV + FP = 2 + 29 + 480 + 10 = 521 lines x 32 ms = 16.672 ms 1/60 Hz = 16.67 ms

  9. VGA Controller entity vgaController is Port ( mclk, clr : in std_logic; hs : out std_logic; vs : out std_logic; red : out std_logic; grn : out std_logic; blu : out std_logic); end vgaController;

  10. VGA Controller architecture Behavioral of vgaController is constant hpixels: std_logic_vector(9 downto 0) := "1100100000"; --Value of pixels in a horizontal line = 800 constant vlines: std_logic_vector(9 downto 0) := "1000001001"; --Number of horizontal lines in the display = 521 constant hbp: std_logic_vector(9 downto 0) := "0010010000"; --Horizontal back porch = 144 (128+16) constant hfp: std_logic_vector(9 downto 0) := "1100010000"; --Horizontal front porch = 784 (128+16+640) constant vbp: std_logic_vector(9 downto 0) := "0000011111"; --Vertical back porch = 31 (2+29) constant vfp: std_logic_vector(9 downto 0) := "0111111111"; --Vertical front porch = 511 (2+29+480) signal hc, vc: std_logic_vector(9 downto 0); --These are the Horizontal and Vertical counters

  11. VGA Controller signal clkdiv : std_logic; --Clock divider signal vidon : std_logic; --Tells whether or not its ok to display data signal vsenable: std_logic; --Enable for the Vertical counter begin --This cuts the 50Mhz clock in half process(mclk, clr) begin if clr = '1' then clkdiv <= '0'; elsif(mclk = '1' and mclk'EVENT) then clkdiv <= not clkdiv; end if; end process;

  12. VGA Controller --Runs the horizontal counter process(clkdiv) begin if clr = '1' then hc <= "0000000000"; elsif(clkdiv = '1' and clkdiv'EVENT) then if hc = hpixels then --If the counter has reached the end of pixel count hc <= "0000000000"; --reset the counter vsenable <= '1'; --Enable the vertical counter to increment else hc <= hc + 1; --Increment the horizontal counter vsenable <= '0'; --Leave the vsenable off end if; end if; end process; hs <= '0' when hc(9 downto 7) = "000" else '1'; --Horizontal Sync Pulse is low when hc is 0 - 127

  13. VGA Controller --Runs the vertical counter process(clkdiv) begin if clr = '1' then vc <= "0000000000"; elsif(clkdiv = '1' and clkdiv'EVENT and vsenable = '1') then --Increment when enabled if vc = vlines then --Reset when the number of lines is reached vc <= "0000000000"; else vc <= vc + 1; --Increment the vertical counter end if; end if; end process; vs <= '0' when vc(9 downto 1) = "000000000" else '1'; --Vertical Sync Pulse is low when vc is 0 or 1

  14. VGA Controller red <= '1' when (hc = "1010101100" and vidon ='1') else '0'; --Red pixel on at a horizontal count = 684 = 144 + 540 grn <= '1' when (hc = "0100000100" and vidon ='1') else '0'; --Green pixel on at a horizontal count = 260 = 144 + 116 blu <= '1' when (vc = "0100100001" and vidon ='1') else '0'; --Blue pixel on at a vertical count = 289 = 31 + 258 vidon <= '1' when (((hc < hfp) and (hc > hbp)) and ((vc < vfp) and (vc > vbp))) else '0'; --Enable video out when within the porches end Behavioral;

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