--
-- EnvelopeGenerator.vhd
-- The envelope generator module of VM2413
--
-- Copyright (c) 2006 Mitsutaka Okazaki (brezza@pokipoki.org)
-- All rights reserved.
--
-- Redistribution and use of this source code or any derivative works, are
-- permitted provided that the following conditions are met:
--
-- 1. Redistributions of source code must retain the above copyright notice,
--    this list of conditions and the following disclaimer.
-- 2. Redistributions in binary 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.
-- 3. Redistributions may not be sold, nor may they be used in a commercial
--    product or activity without specific prior written permission.
--
-- THIS SOFTWARE 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 COPYRIGHT OWNER 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 SOFTWARE, EVEN IF
-- ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
--
--
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
use WORK.VM2413.ALL;

entity EnvelopeGenerator is
port (clk    : in std_logic;
      reset  : in std_logic;
      clkena : in std_logic;

      slot   : in SLOT_TYPE;
      stage  : in STAGE_TYPE;
      rhythm : in std_logic;

      am     : in AM_TYPE;
      tl     : in DB_TYPE;
      ar     : in AR_TYPE;
      dr     : in DR_TYPE;
      sl     : in SL_TYPE;
      rr     : in RR_TYPE;
      rks    : in RKS_TYPE;
      key    : in std_logic;

      egout  : out DB_TYPE);
end EnvelopeGenerator;

architecture RTL of EnvelopeGenerator is

  component EnvelopeMemory port (
    clk     : in std_logic;
    reset   : in std_logic;

    waddr   : in SLOT_TYPE;
    wr      : in std_logic;
    wdata   : in EGDATA_TYPE;
    raddr   : in SLOT_TYPE;
    rdata   : out EGDATA_TYPE
    );
  end component;

  component AttackTable port (
    clk     : in std_logic;
    addr    : in integer range 0 to 2 ** (DB_TYPE'high+1) - 1;
    data    : out DB_TYPE
    );
  end component;

  signal rslot : SLOT_TYPE;
  signal memin, memout : EGDATA_TYPE;
  signal memwr : std_logic;

  signal aridx : integer range 0 to 2 ** (DB_TYPE'high+1) - 1;
  signal ardata : DB_TYPE;

begin

  ARTBL : AttackTable port map ( clk, aridx, ardata );
  EGMEM : EnvelopeMemory port map ( clk, reset, slot, memwr, memin, rslot, memout );

  process(clk, reset)

    variable lastkey : std_logic_vector(MAXSLOT-1 downto 0);
    variable rm : std_logic_vector(4 downto 0);
    variable egtmp : std_logic_vector(DB_TYPE'high + 2 downto 0);
    variable ntable : std_logic_vector(17 downto 0);
    variable amphase : std_logic_vector(19 downto 0);
    variable rslot_buf : SLOT_TYPE;
    variable egphase : EGPHASE_TYPE;
    variable egstate : EGSTATE_TYPE;
    variable dphase : EGPHASE_TYPE;

  begin

    if(reset = '1') then

      rm := (others=>'0');
      lastkey := (others=>'0');
      ntable  := (others=>'1');
      amphase(amphase'high downto amphase'high-4) := "00001";
      amphase(amphase'high-5 downto 0) := (others=>'0');
      memwr <= '0';
      egstate := Finish;
      egphase := (others=>'0');
      rslot_buf := 0;

    elsif(clk'event and clk='1') then if clkena ='1' then

      -- White noise generator
      for I in 17 downto 1 loop
        ntable(I) := ntable(I-1);
      end loop;
      ntable(0) := ntable(17) xor ntable(14);

      -- Amplitude oscillator ( -4.8dB to 0dB , 3.7Hz )
      amphase := amphase + '1';
      if amphase(amphase'high downto amphase'high-4) = "11111" then
        amphase(amphase'high downto amphase'high-4) := "00001";
      end if;

      if stage = 0 then

        egstate := memout.state;
        egphase := memout.phase;
        aridx <= CONV_INTEGER( egphase( egphase'high-1 downto egphase'high-7 ) );

      elsif stage = 1 then

        -- Wait for AttackTable

      elsif stage = 2 then

        case egstate is
          when Attack =>
            rm := '0'&ar;
            egtmp := ("00"&tl) + ("00"&ardata);
          when Decay  =>
            rm := '0'&dr;
            egtmp := ("00"&tl) + ("00"&egphase(egphase'high-1 downto egphase'high-7));
          when Release=>
            rm := '0'&rr;
            egtmp := ("00"&tl) + ("00"&egphase(egphase'high-1 downto egphase'high-7));
          when Finish =>
            egtmp(egtmp'high downto egtmp'high -1) := "00";
            egtmp(egtmp'high-2 downto 0) := (others=>'1');
        end case;

        -- SD and HH
        if ntable(0)='1' and slot/2 = 7 and rhythm = '1' then
          egtmp := egtmp + "010000000";
        end if;

        -- Amplitude LFO
        if am ='1' then
          if (amphase(amphase'high) = '0') then
            egtmp := egtmp + ("00000"&(amphase(amphase'high-1 downto amphase'high-4)-'1'));
          else
            egtmp := egtmp + ("00000"&("1111"-amphase(amphase'high-1 downto amphase'high-4)));
          end if;
        end if;

        -- Generate output
        if egtmp(egtmp'high downto egtmp'high-1) = "00" then
          egout <= egtmp(egout'range);
        else
          egout <= (others=>'1');
        end if;

        if rm /= "00000" then

          rm := rm + rks(3 downto 2);
          if rm(rm'high)='1' then
            rm(3 downto 0):="1111";
          end if;

          case egstate is
            when Attack =>
              dphase(dphase'high downto 5) := (others=>'0');
              dphase(5 downto 0) := "110" * ('1'&rks(1 downto 0));
              dphase := SHL( dphase, rm(3 downto 0) );
              egphase := egphase - dphase(egphase'range);
            when Decay | Release =>
              dphase(dphase'high downto 3) := (others=>'0');
              dphase(2 downto 0) := '1'&rks(1 downto 0);
              dphase  := SHL(dphase, rm(3 downto 0) - '1');
              egphase := egphase + dphase(egphase'range);
            when Finish =>
              null;
          end case;

        end if;

        case egstate is
          when Attack =>
            if egphase(egphase'high) = '1' then
              egphase := (others=>'0');
              egstate := Decay;
            end if;
          when Decay =>
            if egphase(egphase'high downto egphase'high-4) >= '0'&sl then
              egstate := Release;
            end if;
          when Release =>
            if( egphase(egphase'high downto egphase'high-4) >= "01111" ) then
              egstate:= Finish;
            end if;
          when Finish =>
            egphase := (others => '1');
        end case;

        if lastkey(slot) = '0' and key = '1' then
          egphase(egphase'high):= '0';
          egphase(egphase'high-1 downto 0) := (others =>'1');
          egstate:= Attack;
        elsif lastkey(slot) = '1' and key = '0' and egstate /= Finish then
          egstate:= Release;
        end if;
        lastkey(slot) := key;

        -- update phase and state memory
        memin <= ( state => egstate, phase => egphase );
        memwr <='1';

        -- read phase of next slot (prefetch)
        if slot = 17 then
          rslot_buf := 0;
        else
          rslot_buf := slot + 1;
        end if;
        rslot <= rslot_buf;

      elsif stage = 3 then

        -- wait for phase memory
        memwr <='0';

      end if;

    end if; end if;

  end process;

end RTL;

