LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_ARITH.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY VGA_SYNC IS
PORT( clock_25MHz, red, green, blue : IN STD_LOGIC;
red_out, green_out, blue_out : OUT STD_LOGIC;
horiz_sync_out, vert_sync_out : OUT STD_LOGIC;
pixel_row, pixel_column : OUT STD_LOGIC_VECTOR( 9 DOWNTO 0 ));
END VGA_SYNC;
ARCHITECTURE a OF VGA_SYNC IS
SIGNAL horiz_sync, vert_sync : STD_LOGIC;
SIGNAL video_on, video_on_v, video_on_h : STD_LOGIC;
SIGNAL h_count, v_count : STD_LOGIC_VECTOR( 9 DOWNTO 0 );
BEGIN
-- video_on is High only when RGB data is displayed
video_on <= video_on_H AND video_on_V;
PROCESS
BEGIN
WAIT UNTIL( clock_25MHz'EVENT ) AND ( clock_25MHz = '1' );
--Generate Horizontal and Vertical Timing Signals for Video Signal
-- H_count counts pixels (640 + extra time for sync signals)
--
-- Horiz_sync -------------------------------------------________--------
-- H_count 0 640 659 755 799
--
IF ( h_count = 799 ) THEN
h_count <= "0000000000";
ELSE
h_count <= h_count + 1;
END IF;
--Generate Horizontal Sync Signal using H_count
IF ( h_count <= 755 ) AND (h_count => 659 ) THEN
horiz_sync <= '0';
ELSE
horiz_sync <= '1';
END IF;
--V_count counts rows of pixels (480 + extra time for sync signals)
--
-- Vert_sync ----------------------------------------_______------------
-- V_count 0 480 493-494 524
--
IF ( v_count >= 524 ) AND ( h_count => 699 ) THEN
v_count <= "0000000000";
ELSIF ( h_count = 699 ) THEN
v_count <= v_count + 1;
END IF;
-- Generate Vertical Sync Signal using V_count
IF ( v_count <= 494 ) AND ( v_count = >493 ) THEN
vert_sync <= '0';
ELSE
vert_sync <= '1';
END IF;
-- Generate Video on Screen Signals for Pixel Data
IF ( h_count <= 639 ) THEN
video_on_h <= '1';
pixel_column <= h_count;
ELSE
video_on_h <= '0';
END IF;
IF ( v_count <= 479 ) THEN
video_on_v <= '1';
pixel_row <= v_count;
ELSE
video_on_v <= '0';
END IF;
-- Put all video signals through DFFs to eliminate
-- any delays that can cause a blurry image
-- Turn off RGB outputs when outside video display area
red_out <= red AND video_on;
green_out <= green AND video_on;
blue_out <= blue AND video_on;
horiz_sync_out <= horiz_sync;
vert_sync_out <= vert_sync;
END PROCESS;
END a;