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MouseCursor.vhd
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MouseCursor.vhd
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------------------------------------------------------------------------
-- mouse_displayer.vhd
------------------------------------------------------------------------
-- Author : Ulrich Zoltán
-- Copyright 2006 Digilent, Inc.
------------------------------------------------------------------------
-- Software version : Xilinx ISE 7.1.04i
-- WebPack
-- Device : 3s200ft256-4
------------------------------------------------------------------------
-- This file contains the implementation of a mouse cursor.
------------------------------------------------------------------------
-- Behavioral description
------------------------------------------------------------------------
-- Mouse position is received from the mouse_controller, horizontal and
-- vertical counters are received from vga_module and if the counters
-- are inside the mouse cursor bounds, then the mouse is sent to the
-- screen instead of the received pixels. The mouse cursor is 16x16
-- pixels and used 2 colors: white and black. For the color encoding
-- 2 bits are used to be able to use transparency. The cursor is stored
-- in a distributed ram memory 256x2bits in dimension. If the current
-- pixel of the mouse is "00" then output color is black, if "01" then
-- white and if "10" or "11" then the pixel is perfectly transparent
-- and the input colors are output. This way, the mouse will not be a
-- 16x16 square and will have an arrow shape.
-- Memory address is composed from the difference of the vga counters
-- and mouse position. xdiff is the difference on 4 bits (because cursor
-- is 16 pixels width) between the horizontal vga counter and the xpos
-- of the mouse. ydiff is the difference on 4 bits (because cursor
-- has 16 pixels in height) between the vertical vga counter and the
-- ypos of the mouse. By concatenating ydiff and xidff (in this order)
-- the memory address of the current pixel is obtained.
-- Distributed memory is forced by the attributes, because the block
-- rams are entirely used for storing images.
-- If blank input from the vga_module is active, this means that current
-- pixel is not inside visible screen and color outputs are set to black
------------------------------------------------------------------------
-- Port definitions
------------------------------------------------------------------------
-- clk - global clock signal (100MHz)
-- pixel_clk - input pin, from pixel_clock_switcher, the clock used
-- - by the vga_controller for the currently used
-- - resolution, generated by a dcm. 25MHz for 640x480
-- - and 40MHz for 800x600. This clock is used to read
-- - pixels from memory and output data on color outputs.
-- xpos - input pin, 10 bits, from mouse_controller
-- - the x position of the mouse relative to the upper
-- - left corner
-- ypos - input pin, 10 bits, from mouse_controller
-- - the y position of the mouse relative to the upper
-- - left corner
-- hcount - input pin, 11 bits, from vga_module
-- - the horizontal counter from the vga_controller
-- - tells the horizontal position of the current pixel
-- - on the screen from left to right.
-- vcount - input pin, 11 bits, from vga_module
-- - the vertical counter from the vga_controller
-- - tells the vertical position of the currentl pixel
-- - on the screen from top to bottom.
-- blank - input pin, from vga_module
-- - if active, current pixel is not in visible area,
-- - and color outputs should be set on 0.
-- red_in - input pin, 4 bits, from effects_layer
-- - red channel input of the image to be displayed
-- green_in - input pin, 4 bits, from effects_layer
-- - green channel input of the image to be displayed
-- blue_in - input pin, 4 bits, from effects_layer
-- - blue channel input of the image to be displayed
-- red_out - output pin, 4 bits, to vga hardware module.
-- - red output channel
-- green_out - output pin, 4 bits, to vga hardware module.
-- - green output channel
-- blue_out - output pin, 4 bits, to vga hardware module.
-- - blue output channel
------------------------------------------------------------------------
-- Revision History:
-- 09/18/2006(UlrichZ): created
-- 10/29/2006(MirceaD): modified for Basys:
-- color busses reduced to 3-3-2 bits
------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
-- simulation library
library UNISIM;
use UNISIM.VComponents.all;
-- the mouse_displayer entity declaration
-- read above for behavioral description and port definitions.
entity mouse_displayer is
port (
clk : in std_logic;
pixel_clk: in std_logic;
xpos : in std_logic_vector(9 downto 0);
ypos : in std_logic_vector(9 downto 0);
hcount : in std_logic_vector(10 downto 0);
vcount : in std_logic_vector(10 downto 0);
blank : in std_logic;
red_in : in std_logic_vector(3 downto 0);
green_in : in std_logic_vector(3 downto 0);
blue_in : in std_logic_vector(3 downto 0);
red_out : out std_logic_vector(3 downto 0);
green_out: out std_logic_vector(3 downto 0);
blue_out : out std_logic_vector(3 downto 0)
);
-- force synthesizer to extract distributed ram for the
-- displayrom signal, and not a block ram, because the block ram
-- is entirely used to store the image.
attribute rom_extract : string;
attribute rom_extract of mouse_displayer: entity is "yes";
attribute rom_style : string;
attribute rom_style of mouse_displayer: entity is "distributed";
end mouse_displayer;
architecture Behavioral of mouse_displayer is
------------------------------------------------------------------------
-- CONSTANTS
------------------------------------------------------------------------
type displayrom is array(0 to 255) of std_logic_vector(1 downto 0);
-- the memory that holds the cursor.
-- 00 - black
-- 01 - white
-- 1x - transparent
constant mouserom: displayrom := (
"00","00","11","11","11","11","11","11","11","11","11","11","11","11","11","11",
"00","01","00","11","11","11","11","11","11","11","11","11","11","11","11","11",
"00","01","01","00","11","11","11","11","11","11","11","11","11","11","11","11",
"00","01","01","01","00","11","11","11","11","11","11","11","11","11","11","11",
"00","01","01","01","01","00","11","11","11","11","11","11","11","11","11","11",
"00","01","01","01","01","01","00","11","11","11","11","11","11","11","11","11",
"00","01","01","01","01","01","01","00","11","11","11","11","11","11","11","11",
"00","01","01","01","01","01","01","01","00","11","11","11","11","11","11","11",
"00","01","01","01","01","01","00","00","00","00","11","11","11","11","11","11",
"00","01","01","01","01","01","00","11","11","11","11","11","11","11","11","11",
"00","01","00","00","01","01","00","11","11","11","11","11","11","11","11","11",
"00","00","11","11","00","01","01","00","11","11","11","11","11","11","11","11",
"00","11","11","11","00","01","01","00","11","11","11","11","11","11","11","11",
"11","11","11","11","11","00","01","01","00","11","11","11","11","11","11","11",
"11","11","11","11","11","00","01","01","00","11","11","11","11","11","11","11",
"11","11","11","11","11","11","00","00","11","11","11","11","11","11","11","11"
);
-- width and height of cursor.
constant OFFSET: std_logic_vector(4 downto 0) := "10000"; -- 16
------------------------------------------------------------------------
-- SIGNALS
------------------------------------------------------------------------
--signal rompos: std_logic_vector(7 downto 0) := (others => '0');
-- pixel from the display memory, representing currently displayed
-- pixel of the cursor, if the cursor is being display at this point
signal mousepixel: std_logic_vector(1 downto 0) := (others => '0');
-- when high, enables displaying of the cursor, and reading the
-- cursor memory.
signal enable_mouse_display: std_logic := '0';
-- difference in range 0-15 between the vga counters and mouse position
signal xdiff: std_logic_vector(3 downto 0) := (others => '0');
signal ydiff: std_logic_vector(3 downto 0) := (others => '0');
begin
-- compute xdiff
x_diff: process(clk)
variable temp_diff: std_logic_vector(10 downto 0) := (others => '0');
begin
if(rising_edge(clk)) then
temp_diff := hcount - ('0' & xpos);
xdiff <= temp_diff(3 downto 0);
end if;
end process x_diff;
-- compute ydiff
y_diff: process(clk)
variable temp_diff: std_logic_vector(10 downto 0) := (others => '0');
begin
if(rising_edge(clk)) then
temp_diff := vcount - ('0' & ypos);
ydiff <= temp_diff(3 downto 0);
end if;
end process y_diff;
-- read pixel from memory at address obtained by concatenation of
-- ydiff and xdiff
mousepixel <= mouserom(conv_integer(ydiff & xdiff))
when rising_edge(pixel_clk);
-- set enable_mouse_display high if vga counters inside cursor block
enable_mouse: process(pixel_clk)
begin
if(rising_edge(pixel_clk)) then
if(hcount >= xpos and hcount < (xpos + OFFSET) and
vcount >= ypos and vcount < (ypos + OFFSET))
then
enable_mouse_display <= '1';
else
enable_mouse_display <= '0';
end if;
end if;
end process enable_mouse;
-- if cursor display is enabled, then, according to pixel
-- value, set the output color channels.
process(pixel_clk)
begin
if(rising_edge(pixel_clk)) then
-- if in visible screen
if(blank = '0') then
-- in display is enabled
if(enable_mouse_display = '1') then
-- white pixel of cursor
if(mousepixel = "01") then
red_out <= (others => '1');
green_out <= (others => '1');
blue_out <= (others => '1');
-- black pixel of cursor
elsif(mousepixel = "00") then
red_out <= (others => '0');
green_out <= (others => '0');
blue_out <= (others => '0');
-- transparent pixel of cursor
-- let input pass to output
else
red_out <= red_in;
green_out <= green_in;
blue_out <= blue_in;
end if;
-- cursor display is not enabled
-- let input pass to output.
else
red_out <= red_in;
green_out <= green_in;
blue_out <= blue_in;
end if;
-- not in visible screen, black outputs.
else
red_out <= (others => '0');
green_out <= (others => '0');
blue_out <= (others => '0');
end if;
end if;
end process;
end Behavioral;