ball.vhd

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.all;
USE  IEEE.STD_LOGIC_ARITH.all;
USE  IEEE.STD_LOGIC_UNSIGNED.all;


ENTITY ball IS
	PORT
		( clk 						: IN std_logic;
		  pixel_row, pixel_column	: IN std_logic_vector(9 DOWNTO 0);
		  red, green, blue 			: OUT std_logic);		
END ball;

architecture behavior of ball is

SIGNAL ball_on					: std_logic;
SIGNAL size 					: std_logic_vector(9 DOWNTO 0);  
SIGNAL ball_y_pos, ball_x_pos	: std_logic_vector(9 DOWNTO 0);

BEGIN           

size <= CONV_STD_LOGIC_VECTOR(15,10);
-- ball_x_pos and ball_y_pos show the (x,y) for the centre of ball
ball_x_pos <= CONV_STD_LOGIC_VECTOR(590,10);
ball_y_pos <= CONV_STD_LOGIC_VECTOR(59,10);


ball_on <= '1' when ( ('0' & ball_x_pos <= pixel_column + size) 
					and ('0' & pixel_column <= ball_x_pos + size) 	-- x_pos - size <= pixel_column <= x_pos + size
					and ('0' & ball_y_pos <= pixel_row + size) 
					and ('0' & pixel_row <= ball_y_pos + size) )  else	-- y_pos - size <= pixel_row <= y_pos + size
			  '0';


-- Colours for pixel data on video signal
-- Keeping background white and square in red
Red <=  '1';
-- Turn off Green and Blue when displaying square
Green <= not ball_on;
Blue <=  not ball_on;

END behavior;