library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;


--  Uncomment the following lines to use the declarations that are
--  provided for instantiating Xilinx primitive components.
--library UNISIM;
--use UNISIM.VComponents.all;

entity SATURN is

		Port (
				--SATURN
				Address : in std_logic_vector(25 downto 1);
				Data : inout std_logic_vector(15 downto 0);
				WE : in std_logic;
				OE : in std_logic;
				CE : in std_logic;

				--FX2
				PB : inout std_logic_vector(7 downto 0);
				FX2_CLK : in std_logic;
				CTL0 : in std_logic;
				CTL1 : in std_logic;
				CTL2 : in std_logic;
				RDY0 :	out std_logic;

				--FLASH
				fOE : out std_logic;
				fCE : out std_logic;

				--DEBUG2 : in std_logic;
				LED : out std_logic;
				DEBUG : out std_logic_vector(2 downto 0) 
				);      

end SATURN;


architecture Behavioral of SATURN is

signal	data1 : std_logic_vector(7 downto 0);
signal	flag  : std_logic:='0';


begin

PB<=data1 when CTL0='1' else
		(others=>'Z');

RDY0<=flag;

process(FX2_CLK,Data,Address)
begin

	fCE<='1';
	fOE<='1';
	Data(7 downto 0)<=(others=>'Z');
	flag<='1';

	if(Address(25 downto 19)="1000000")then	--FLASH mem
		if(WE='1')then
		fOE<='0';
		else
		fOE<='1';
		end if;
		fCE<='0';
--EMS rip of datel firmware with hacked register locations
	elsif(Address(25 downto 19)="1000001")then --Data output to Comms Link	 $02080001 
		if(WE='0')then
			data1<=Data(7 downto 0);
			flag<='0';
		end if;

	elsif(Address(25 downto 19)="1000010")then --status flag in bit 0	$02100001
		if(WE='1')then
		Data(0)<=not CTL1;
		else
		Data(0)<='Z';
		end if;

	elsif(Address(25 downto 19)="1000011")then --Data input from Comms Link	 $02180001
		if(WE='1')then
		Data(7 downto 0)<=PB;
		else
		Data(7 downto 0)<=(others=>'Z');
		end if;
--Datel locations of comms registers
	elsif(Address(25 downto 19)="1001000")then --Data output to Comms Link	 $02400001 
		if(WE='0')then
			data1<=Data(7 downto 0);
			flag<='0';
		end if;

	elsif(Address(25 downto 19)="1001010")then --status flag in bit 0	$02500001
		if(WE='1')then
		Data(0)<=not CTL1;
		else
		Data(0)<='Z';
		end if;

	elsif(Address(25 downto 19)="1001100")then --Data input from Comms Link	$02600001
		if(WE='1')then
		Data(7 downto 0)<=PB;
		else
		Data(7 downto 0)<=(others=>'Z');
		end if;
--Drive 0xFD on the databus to 0x03000000 and beyond , the cart uses this as a sort of signature, firmware requires it unless you wanna patch it
	elsif(Address(25 downto 24)="11")then
		if(WE='1')then
		Data(1)<='0';
		else
		Data(1)<='Z';
		end if;

	else
	fCE<='1';
	fOE<='1';
	Data(7 downto 0)<=(others=>'Z');
	end if;		




end process;

--FX2 process:
--when CTL0=1 then read data 
--when CTL0=0 then write data
-- CTL1 is status flag to tell saturn data was written

end Behavioral;