demistify_config_pkg.vhd

-- DeMiSTifyConfig_pkg.vhd
-- Copyright 2021 by Alastair M. Robinson

library ieee;
use ieee.std_logic_1164.all;

package demistify_config_pkg is
constant demistify_romspace : integer := 14; -- 16k address space to accommodate 12K of ROM
constant demistify_romsize1 : integer := 13; -- 8k fot the first chunk
constant demistify_romsize2 : integer := 12; -- 4k for the second chunk, mirrored across the last 4k

-- Core-specific button mapping.
-- Joysticks are (currently) 8 bits width, with the directions in the lower four bits.
-- Button 1 is the main fire button, Button 2 is the secondary fire button to the right of button 1
-- Button 3 is a third (possibly less conveniently placed) button 
-- Button 4 is mapped as a "start" or "run" button.

-- By adjusting the following constants you can assign each button a place in the joystick bitmap.
-- The Megadrive core, for instance, expects the following bitmap:
-- start(7) C(6) B(5) A(4) directions(3:0)
-- Since Megadrive button B is the most important, we map button 1 -> B, button 2 -> C, button 3 -> A
-- and button 4 -> Start, hence button1 = 5, button2 = 6, button3 = 4 and button4 = 7,

constant demistify_button1 : integer := 4;
constant demistify_button2 : integer := 5;
constant demistify_button3 : integer := 6;
constant demistify_button4 : integer := 7;

constant demistify_serialdebug : std_logic := '0';


end package;