-------------------------------------------------------------------------------
-- Title      : vga_control architecture
-- Project    : LU Digital Design
-------------------------------------------------------------------------------
-- File       : vga_control.vhd
-- Author     : Thomas Handl
-- Company    : TU Wien
-- Created    : 2004-12-15
-- Last update: 2006-02-24
-------------------------------------------------------------------------------
-- Description: generation of colors (RGB)
-------------------------------------------------------------------------------
-- Copyright (c) 2004 TU Wien
-------------------------------------------------------------------------------
-- Revisions  :
-- Date        Version  Author  Description
-- 2004-12-15  1.0      handl   Created
-- 2006-02-24  2.0      ST      revised
-------------------------------------------------------------------------------

-------------------------------------------------------------------------------
-- LIBRARIES
-------------------------------------------------------------------------------

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_unsigned.all;
use IEEE.std_logic_arith.all;

use work.vga_pak.all;

-------------------------------------------------------------------------------
-- ARCHITECTURE
-------------------------------------------------------------------------------

architecture behav of vga_control is


  attribute syn_preserve          : boolean;
  attribute syn_preserve of behav : architecture is true;
  signal   r_next, g_next, b_next  : std_logic;

begin
  DRAW_SQUARE_syn: process(clk, reset)
  begin
    if (reset = RES_ACT) then   -- draw black screen upon reset
      r <= COLR_OFF;
      g <= COLR_OFF;
      b <= COLR_OFF;
    elsif (clk'event and clk = '1') then     -- synchronous capture
      r <= r_next;
      g <= g_next;
      b <= b_next;
    end if;
  end process;


  DRAW_SQUARE_next: process (column_counter, v_enable, h_enable)
  begin
	  if v_enable = ENABLE and h_enable = ENABLE then        
		  if (column_counter >= X_MIN and column_counter < X2_MIN) then   -- if pixel within the rectangle borders
			  r_next <= COLR_OFF;
			  g_next <= COLR_OFF;
			  b_next <= COLR_ON;
		  elsif (column_counter >= X2_MIN and column_counter < X3_MIN) then   -- if pixel within the rectangle borders
			  r_next <= COLR_OFF;
			  g_next <= COLR_ON;
			  b_next <= COLR_ON;
		  elsif (column_counter >= X3_MIN and column_counter < X_MAX) then   -- if pixel within the rectangle borders
			  r_next <= COLR_ON;
			  g_next <= COLR_OFF;
			  b_next <= COLR_ON;
		  else                                                           -- if somewhere else on screen...
			  r_next <= COLR_OFF;
			  g_next <= COLR_OFF;                                          -- ... draw background color
			  b_next <= COLR_OFF;
		  end if;
	  else                                                             -- if out of screen...
		  r_next <= COLR_OFF;
		  g_next <= COLR_OFF;                                            -- ... do not activate any color
		  b_next <= COLR_OFF;                                            --     (black screen)
	  end if;
  end process;

end behav;

-------------------------------------------------------------------------------
-- END ARCHITECTURE
-------------------------------------------------------------------------------