vga_font_generator.v

   1 /*
   2  * Copyright 2018 Jacob Lifshay
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a copy
   5  * of this software and associated documentation files (the "Software"), to deal
   6  * in the Software without restriction, including without limitation the rights
   7  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   8  * copies of the Software, and to permit persons to whom the Software is
   9  * furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included in all
  12  * copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  17  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  18  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  19  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  20  * SOFTWARE.
  21  *
  22  */
  23 `timescale 1ns / 100ps
  24
  25 module vga_font_generator(
  26         input pixel_clock,
  27     input [15:0] screen_x,
  28     input [15:0] screen_y,
  29     input screen_valid,
  30     input [7:0] screen_char,
  31         output [7:0] vga_r,
  32         output [7:0] vga_g,
  33         output [7:0] vga_b
  34     );
  35
  36     parameter font_x_size = 8;
  37     parameter font_y_size = 8;
  38
  39     // ram_style = "block"
  40     reg [font_x_size - 1 : 0] font8x8[0 : 256 * font_y_size - 1];
  41
  42     initial $readmemh("font8x8.hex", font8x8);
  43
  44     wire [2:0] sub_char_x = screen_x[2:0];
  45     wire [2:0] sub_char_y = screen_y[2:0];
  46     wire [15:0] font_address = {screen_char, sub_char_y};
  47     reg [7:0] font_line;
  48     reg [2:0] output_sub_char_x;
  49
  50     initial font_line = 0;
  51     initial output_sub_char_x = 0;
  52
  53     always @(posedge pixel_clock) begin
  54         font_line <= font8x8[font_address];
  55         output_sub_char_x <= sub_char_x;
  56     end
  57
  58     wire pixel_active = ((font_line >> output_sub_char_x) & 1) == 1;
  59     assign vga_r = pixel_active ? 255 : 0;
  60     assign vga_g = pixel_active ? 255 : 0;
  61     assign vga_b = pixel_active ? 255 : 0;
  62
  63 endmodule