---------------------------------------------------------------------------
-- (c) 2013 mark watson
-- I am happy for anyone to use this for non-commercial use.
-- If my vhdl files are used commercially or otherwise sold,
-- please contact me for explicit permission at scrameta (gmail).
-- This applies for source and binary form and derived works.
---------------------------------------------------------------------------
LIBRARY ieee;
USE ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use IEEE.STD_LOGIC_MISC.all;

ENTITY pokey_mixer IS
PORT 
( 
	SUM : IN unsigned(5 downto 0);
	
	SATURATE : IN std_logic; -- pokey style curve or linear
	
	VOLUME_OUT_NEXT : OUT std_logic_vector(15 downto 0)
);
END pokey_mixer;

ARCHITECTURE vhdl OF pokey_mixer IS

	function pokeyvolume(x: unsigned(5 downto 0)) return unsigned is
	begin
		case x is
when "000000" => return x"0022";
when "000001" => return x"0993";
when "000010" => return x"135E";
when "000011" => return x"1D9A";
when "000100" => return x"2842";
when "000101" => return x"3345";
when "000110" => return x"3E84";
when "000111" => return x"49E0";
when "001000" => return x"5538";
when "001001" => return x"606E";
when "001010" => return x"6B69";
when "001011" => return x"7612";
when "001100" => return x"805A";
when "001101" => return x"8A34";
when "001110" => return x"9399";
when "001111" => return x"9C84";
when "010000" => return x"A4F4";
when "010001" => return x"ACEA";
when "010010" => return x"B468";
when "010011" => return x"BB70";
when "010100" => return x"C207";
when "010101" => return x"C830";
when "010110" => return x"CDEE";
when "010111" => return x"D343";
when "011000" => return x"D833";
when "011001" => return x"DCC0";
when "011010" => return x"E0EB";
when "011011" => return x"E4B6";
when "011100" => return x"E824";
when "011101" => return x"EB36";
when "011110" => return x"EDEF";
when "011111" => return x"F053";
when "100000" => return x"F265";
when "100001" => return x"F42B";
when "100010" => return x"F5AB";
when "100011" => return x"F6E9";
when "100100" => return x"F7EF";
when "100101" => return x"F8C3";
when "100110" => return x"F96D";
when "100111" => return x"F9F4";
when "101000" => return x"FA61";
when "101001" => return x"FABB";
when "101010" => return x"FB07";
when "101011" => return x"FB4C";
when "101100" => return x"FB8D";
when "101101" => return x"FBCE";
when "101110" => return x"FC11";
when "101111" => return x"FC56";
when "110000" => return x"FC9F";
when "110001" => return x"FCEA";
when "110010" => return x"FD37";
when "110011" => return x"FD85";
when "110100" => return x"FDD5";
when "110101" => return x"FE28";
when "110110" => return x"FE82";
when "110111" => return x"FEE7";
when "111000" => return x"FF5D";
when "111001" => return x"FFEB";
when "111010" => return x"FFFF";
when "111011" => return x"FFFF";
when "111100" => return x"FFFF";		
when others =>
	return x"ffff";
		end case;
	end pokeyvolume;	
BEGIN
	-- next state
 	process (sum,saturate)
	begin
-- saturation on
		if (saturate='1') then
			volume_out_next <= std_logic_vector(pokeyvolume(sum));
		else
-- saturation off
			volume_out_next <= (others=>'0');
			volume_out_next(15 downto 6) <= std_logic_vector(unsigned(SUM&"0000")+unsigned("0000"&SUM));
		end if;
        end process;

END vhdl;