vga.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(
  26     input clk,
  27         output [7:0] vga_r,
  28         output [7:0] vga_g,
  29         output [7:0] vga_b,
  30         output vga_hsync,
  31         output vga_vsync,
  32     output vga_blank,
  33     output vga_pixel_clock,
  34     input tty_write,
  35     input [7:0] tty_data,
  36     output tty_busy
  37     );
  38
  39     wire pixel_clock;
  40
  41     vga_clock_generator clock_generator(clk, pixel_clock);
  42
  43     wire location_generator_hsync;
  44     wire location_generator_vsync;
  45     wire location_generator_blank;
  46     wire [15:0] location_generator_x;
  47     wire [15:0] location_generator_y;
  48     wire location_generator_xy_in_active;
  49
  50     vga_location_generator location_generator(pixel_clock,
  51         location_generator_hsync,
  52         location_generator_vsync,
  53         location_generator_blank,
  54         location_generator_x,
  55         location_generator_y,
  56         location_generator_xy_in_active);
  57
  58     wire [7:0] text_buffer_screen_char;
  59     reg text_buffer_hsync;
  60     reg text_buffer_vsync;
  61     reg text_buffer_blank;
  62     reg [15:0] text_buffer_x;
  63     reg [15:0] text_buffer_y;
  64     reg text_buffer_xy_in_active;
  65
  66     initial text_buffer_hsync = 0;
  67     initial text_buffer_vsync = 0;
  68     initial text_buffer_blank = 0;
  69     initial text_buffer_x = 0;
  70     initial text_buffer_y = 0;
  71     initial text_buffer_xy_in_active = 0;
  72
  73     always @(posedge pixel_clock) text_buffer_hsync <= location_generator_hsync;
  74     always @(posedge pixel_clock) text_buffer_vsync <= location_generator_vsync;
  75     always @(posedge pixel_clock) text_buffer_blank <= location_generator_blank;
  76     always @(posedge pixel_clock) text_buffer_x <= location_generator_x;
  77     always @(posedge pixel_clock) text_buffer_y <= location_generator_y;
  78     always @(posedge pixel_clock) text_buffer_xy_in_active <= location_generator_xy_in_active;
  79
  80     vga_text_buffer text_buffer(pixel_clock,
  81         location_generator_x,
  82         location_generator_y,
  83         location_generator_xy_in_active,
  84         text_buffer_screen_char,
  85         clk,
  86         tty_write,
  87         tty_data,
  88         tty_busy);
  89
  90     wire [7:0] font_generator_r;
  91     wire [7:0] font_generator_g;
  92     wire [7:0] font_generator_b;
  93
  94     vga_font_generator font_generator(
  95         pixel_clock,
  96         text_buffer_x,
  97         text_buffer_y,
  98         text_buffer_xy_in_active,
  99         text_buffer_screen_char,
 100         font_generator_r,
 101         font_generator_g,
 102         font_generator_b);
 103
 104     reg font_generator_hsync;
 105     reg font_generator_vsync;
 106     reg font_generator_blank;
 107
 108     initial font_generator_hsync = 0;
 109     initial font_generator_vsync = 0;
 110     initial font_generator_blank = 0;
 111
 112     always @(posedge pixel_clock) font_generator_hsync <= text_buffer_hsync;
 113     always @(posedge pixel_clock) font_generator_vsync <= text_buffer_vsync;
 114     always @(posedge pixel_clock) font_generator_blank <= text_buffer_blank;
 115
 116     assign vga_pixel_clock = ~pixel_clock;
 117
 118     reg output_hsync;
 119     reg output_vsync;
 120     reg output_blank;
 121     reg [7:0] output_r;
 122     reg [7:0] output_g;
 123     reg [7:0] output_b;
 124
 125     initial output_hsync = 0;
 126     initial output_vsync = 0;
 127     initial output_blank = 0;
 128     initial output_r = 0;
 129     initial output_g = 0;
 130     initial output_b = 0;
 131
 132     always @(posedge pixel_clock) output_hsync = font_generator_hsync;
 133     always @(posedge pixel_clock) output_vsync = font_generator_vsync;
 134     always @(posedge pixel_clock) output_blank = font_generator_blank;
 135     always @(posedge pixel_clock) output_r = font_generator_r;
 136     always @(posedge pixel_clock) output_g = font_generator_g;
 137     always @(posedge pixel_clock) output_b = font_generator_b;
 138
 139         assign vga_r = output_r;
 140         assign vga_g = output_g;
 141         assign vga_b = output_b;
 142
 143         reg final_hsync;
 144         reg final_vsync;
 145     reg final_blank;
 146
 147     initial final_hsync = 0;
 148     initial final_vsync = 0;
 149     initial final_blank = 0;
 150
 151     always @(posedge pixel_clock) final_hsync = output_hsync;
 152     always @(posedge pixel_clock) final_vsync = output_vsync;
 153     always @(posedge pixel_clock) final_blank = font_generator_blank;
 154
 155     assign vga_hsync = final_hsync;
 156     assign vga_vsync = final_vsync;
 157     assign vga_blank = font_generator_blank;
 158 endmodule