git.zerfleddert.de Git - raggedstone/blob - dhwk_old/source/vga_main.vhd

   1 ---------------------------------------------------------------------
   2 -- vga_main.vhd  Demo VGA configuration module.
   3 ---------------------------------------------------------------------
   4 --      Author: Barron Barnett
   5 --            Copyright 2004 Digilent, Inc.
   6 ---------------------------------------------------------------------
   7 --
   8 -- This project is compatible with Xilinx ISE or Xilinx WebPack tools.
   9 --
  10 -- Inputs:
  11 --              mclk  - System Clock
  12 -- Outputs:
  13 --              hs              - Horizontal Sync
  14 --              vs              - Vertical Sync
  15 --              red     - Red Output
  16 --              grn     - Green Output
  17 --              blu     - Blue Output
  18 --
  19 -- This module creates a three line pattern on a vga display using a
  20 -- a vertical refresh rate of 60Hz.  This is done by dividing the
  21 -- system clock in half and using that for the pixel clock.  This in
  22 -- turn drives the vertical sync when the horizontal sync has reached
  23 -- its reset point.  All data displayed is done by basic value
  24 -- comparisons.
  25 ------------------------------------------------------------------------
  26 -- Revision History:
  27 --       07/01/2004(BarronB): created
  28 ------------------------------------------------------------------------
  29 library IEEE;
  30 use IEEE.STD_LOGIC_1164.ALL;
  31 use IEEE.STD_LOGIC_ARITH.ALL;
  32 use IEEE.STD_LOGIC_UNSIGNED.ALL;
  33
  34
  35 entity vgaController is
  36     Port ( mclk : in std_logic;
  37            hs : out std_logic;
  38            vs : out std_logic;
  39            red : out std_logic;
  40            grn : out std_logic;
  41            blu : out std_logic);
  42 end vgaController;
  43
  44 architecture Behavioral of vgaController is
  45
  46
  47         constant hpixels                : std_logic_vector(9 downto 0) := "1100100000";  --Value of pixels in a horizontal line
  48         constant vlines         : std_logic_vector(9 downto 0) := "1000001001";  --Number of horizontal lines in the display
  49
  50         constant hbp                    : std_logic_vector(9 downto 0) := "0010010000";  --Horizontal back porch
  51         constant hfp                    : std_logic_vector(9 downto 0) := "1100010000";  --Horizontal front porch
  52         constant        vbp                     : std_logic_vector(9 downto 0) := "0000011111";  --Vertical back porch
  53         constant vfp                    : std_logic_vector(9    downto 0) := "0111111111";       --Vertical front porch
  54
  55         signal hc, vc                   : std_logic_vector(9 downto 0);                                          --These are the Horizontal and Vertical counters
  56         signal clkdiv                   : std_logic;                                                                                             --Clock divider
  57         signal vidon                    : std_logic;                                                                                             --Tells whether or not its ok to display data
  58         signal vsenable         : std_logic;                                                                                             --Enable for the Vertical counter
  59
  60 begin
  61         --This cuts the 50Mhz clock in half
  62         process(mclk)
  63                 begin
  64                         if(mclk = '1' and mclk'EVENT) then
  65                                 clkdiv <= not clkdiv;
  66                         end if;
  67                 end process;
  68
  69         --Runs the horizontal counter
  70         process(clkdiv)
  71                 begin
  72                         if(clkdiv = '1' and clkdiv'EVENT) then
  73                                 if hc = hpixels then                                                                                                             --If the counter has reached the end of pixel count
  74                                         hc <= "0000000000";                                                                                                      --reset the counter
  75                                         vsenable <= '1';                                                                                                                 --Enable the vertical counter to increment
  76                                 else
  77                                         hc <= hc + 1;                                                                                                                    --Increment the horizontal counter
  78                                         vsenable <= '0';                                                                                                                 --Leave the vsenable off
  79                                 end if;
  80                 end if;
  81         end process;
  82
  83         hs <= '1' when hc(9 downto 7) = "000" else '0';                                                          --Horizontal Sync Pulse
  84
  85         process(clkdiv)
  86         begin
  87                 if(clkdiv = '1' and clkdiv'EVENT and vsenable = '1') then                        --Increment when enabled
  88                         if vc = vlines then                                                                                                                      --Reset when the number of lines is reached
  89                                 vc <= "0000000000";
  90                         else vc <= vc + 1;                                                                                                                       --Increment the vertical counter
  91                         end if;
  92                 end if;
  93         end process;
  94
  95         vs <= '1' when vc(9 downto 1) = "000000000" else '0';                                            --Vertical Sync Pulse
  96
  97         red <= '1' when (hc = "1010101100" and vidon ='1') else '0';                     --Red pixel on at a specific horizontal count
  98         grn <= '1' when (hc = "0100000100" and vidon ='1') else '0';                     --Green pixel on at a specific horizontal count
  99         blu <= '1' when (vc = "0100100001" and vidon ='1') else '0';                     --Blue pixel on at a specific vertical count
 100
 101         vidon <= '1' when (((hc < hfp) and (hc > hbp)) or ((vc < vfp) and (vc > vbp))) else '0';        --Enable video out when within the porches
 102
 103 end Behavioral;