-------------------------------------------------------------------------------
--
-- Williams game board implementation (including VGA scan doubler)
-- for Digilent BASYS3 boards (implemented with Vivado 2017.4 lite).
--
-- The used 6809 CPU is from a different author, released under
-- BSD licence. See readme.txt in te "cpu" folder.
--
-- Delivered WITHOUT ROM content. See readme.txt in the "rom" folder. 
--
-- All other files (main game, basys3 wrapper, blitter, PIA) are 
-- released under the license mentioned here.
--
-- (c) 2016-2021 Wolfgang Scherr, woz <at> pin4.at
-- all rights reserved, use at your own risk
-- http://www.pin4.at/ or https://blog.fh-kaernten.at/retrofusion/
--
-------------------------------------------------------------------------------
--
-- State of implementation:  EARLY ALPHA RELEASE
--
-- Still missing: proper I/O handling (from ROM board and INTERFACE board)
--                implementation of SOUND board
--                better handling of different MAIN board variants
--
-------------------------------------------------------------------------------
-- Redistribution and use in source and synthesized forms, with or without
-- modification, are permitted provided that the following conditions are met:
--
-- Redistributions of source code must retain the above copyright notice,
-- this list of conditions and the following disclaimer.
--
-- Redistributions in synthesized form must reproduce the above copyright
-- notice, this list of conditions and the following disclaimer in the
-- documentation and/or other materials provided with the distribution.
--
-- Neither the name of the author nor the names of other contributors may
-- be used to endorse or promote products derived from this software without
-- specific prior written permission.
--
-- The code and any derivatives must not be used for commercial purposes 
-- without specific prior written permission by the author.
--
-- THIS CODE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE
-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
-- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
-- ARISING IN ANY WAY OUT OF THE USE OF THIS CODE, EVEN IF ADVISED OF THE
-- POSSIBILITY OF SUCH DAMAGE.
----------------------------------------------------------------------------------
