Subversion Repositories spdif_interface

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----                                                              ----

---- WISHBONE SPDIF IP Core                                       ----

----                                                              ----

---- This file is part of the SPDIF project                       ----

---- http://www.opencores.org/cores/spdif_interface/              ----

----                                                              ----

---- Description                                                  ----

---- Sample decoder. Extract sample words and write to sample     ----

---- buffer.                                                      ----

----                                                              ----

----                                                              ----

---- To Do:                                                       ----

---- -                                                            ----

----                                                              ----

---- Author(s):                                                   ----

---- - Geir Drange, gedra@opencores.org                           ----

----                                                              ----

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---- Copyright (C) 2004 Authors and OPENCORES.ORG                 ----

----                                                              ----

---- This source file may be used and distributed without         ----

---- restriction provided that this copyright statement is not    ----

---- removed from the file and that any derivative work contains  ----

---- the original copyright notice and the associated disclaimer. ----

----                                                              ----

---- This source file is free software; you can redistribute it   ----

---- and/or modify it under the terms of the GNU Lesser General   ----

---- Public License as published by the Free Software Foundation; ----

---- either version 2.1 of the License, or (at your option) any   ----

---- later version.                                               ----

----                                                              ----

---- This source is distributed in the hope that it will be       ----

---- useful, but WITHOUT ANY WARRANTY; without even the implied   ----

---- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ----

---- PURPOSE. See the GNU Lesser General Public License for more  ----

---- details.                                                     ----

----                                                              ----

---- You should have received a copy of the GNU Lesser General    ----

---- Public License along with this source; if not, download it   ----

---- from http://www.opencores.org/lgpl.shtml                     ----

----                                                              ----

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--

-- CVS Revision History

--

-- $Log: not supported by cvs2svn $                        

--

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

entity rx_decode is

  generic (DATA_WIDTH: integer range 16 to 32;

           ADDR_WIDTH: integer range 8 to 64);

  port (

    wb_clk_i: in std_logic;

    conf_rxen: in std_logic;

    conf_sample: in std_logic;

    conf_valid: in std_logic;

    conf_mode: in std_logic_vector(3 downto 0);

    conf_blken: in std_logic;

    conf_valen: in std_logic;

    conf_useren: in std_logic;

    conf_staten: in std_logic;

    conf_paren: in std_logic;

    lock: in std_logic;

    rx_data: in std_logic;

    rx_data_en: in std_logic;

    rx_block_start: in std_logic;

    rx_frame_start: in std_logic;

    rx_channel_a: in std_logic;

    wr_en: out std_logic;

    wr_addr: out std_logic_vector(ADDR_WIDTH - 2 downto 0);

    wr_data: out std_logic_vector(DATA_WIDTH downto 0);

    stat_paritya: out std_logic;

    stat_parityb: out std_logic;

    stat_lsbf: out std_logic;

    stat_hsbf: out std_logic);

end rx_decode;

architecture rtl of rx_decode is

  signal adr_cnt : integer range 0 to 2**(ADDR_WIDTH - 1) - 1;

  type samp_states is (IDLE, CHA_SYNC, GET_SAMP, PAR_CHK);

  signal sampst : samp_states;

  signal bit_cnt, par_cnt : integer range 0 to 31;

  signal samp_start : integer range 0 to 15;

  signal tmp_data : std_logic_vector(DATA_WIDTH - 6 downto 0);

  signal tmp_stat : std_logic_vector(4 downto 0);

  signal valid, next_is_a, blk_start : std_logic;

begin

-- sample buffer address

  wr_addr <= CONV_STD_LOGIC_VECTOR(adr_cnt, ADDR_WIDTH - 1);

-- output data

  OD32: if DATA_WIDTH = 32 generate

    wr_data(31 downto 27) <= tmp_stat;

    wr_data(26 downto 0) <= tmp_data(26 downto 0);

  end generate OD32;

  OD16: if DATA_WIDTH = 16 generate

    wr_data(15 downto 0) <= tmp_data(15 downto 0);

  end generate OD16;

-- State machine extracting audio samples

  SAEX: process (wb_clk_i, conf_rxen)

  begin  -- process SAEX

    if conf_rxen = '0' then

      adr_cnt <= 0;

      next_is_a <= '1';

      wr_en <= '0';

      par_cnt <= 0;

      blk_start <= '0';

      stat_paritya <= '0';

      stat_parityb <= '0';

      stat_lsbf <= '0';

      stat_hsbf <= '0';

    elsif rising_edge(wb_clk_i) then

      --extract and store samples

      case sampst is

        when IDLE =>

          next_is_a <= '1';

          if lock = '1' and conf_sample = '1' then

            sampst <= CHA_SYNC;

          end if;

        when CHA_SYNC =>

          wr_en <= '0';

          bit_cnt <= 0;

          valid <= '0';

          par_cnt <= 0;

          stat_paritya <= '0';

          stat_parityb <= '0';

          stat_lsbf <= '0';

          stat_hsbf <= '0';

          tmp_data(DATA_WIDTH - 6 downto 0) <= (others => '0');

          if rx_block_start = '1' and conf_blken = '1' then

            blk_start <= '1';

          end if;

          if rx_frame_start = '1' and rx_channel_a = next_is_a then

            next_is_a <= not next_is_a;

            sampst <= GET_SAMP;

          end if;

        when GET_SAMP =>

          tmp_stat(0) <= blk_start;

          if rx_data_en = '1' then

            -- audio part

            if bit_cnt >= samp_start and bit_cnt <= 23 then

              tmp_data(bit_cnt - samp_start) <= rx_data;

            end if;

            -- status bits

            case bit_cnt is

              when 24 =>                -- validity bit

                valid <= rx_data;

                if conf_valen = '1' then

                  tmp_stat(1) <= rx_data;

                else

                  tmp_stat(1) <= '0';

                end if;

              when 25 =>                -- user data

                if conf_useren = '1' then

                  tmp_stat(2) <= rx_data;

                else

                  tmp_stat(2) <= '0';

                end if;

              when 26 =>                -- channel status

                if conf_staten = '1' then

                  tmp_stat(3) <= rx_data;

                else

                  tmp_stat(3) <= '0';

                end if;

              when 27 =>                -- parity bit

                if conf_paren = '1' then

                  tmp_stat(4) <= rx_data;

                else

                  tmp_stat(4) <= '0';

                end if;

              when others =>

                null;

            end case;

            -- parity: count number of 1's

            par_cnt <= par_cnt + 1;

          end if;

          bit_cnt <= bit_cnt + 1;

          if bit_cnt = 27 then

            sampst <= PAR_CHK;

          end if;

        when PAR_CHK =>

          blk_start <= '0';

          if (valid = '0' and conf_valen = '1') or conf_valen = '0' then

            wr_en <= '1';

          end if;

          -- parity check

          if par_cnt mod 2 /= 0 then

            if rx_channel_a = '1' then

              stat_paritya <= '1';

            else

              stat_parityb <= '1';

            end if;

          end if;

          -- address counter

          if adr_cnt < 2**(ADDR_WIDTH - 1) - 1 then

            adr_cnt <= adr_cnt + 1;

          else

            adr_cnt <= 0;

            stat_hsbf <= '1';           -- signal high buffer full

          end if;

          if adr_cnt = 2**(ADDR_WIDTH - 2) - 1 then

            stat_lsbf <= '1';           -- signal low buffer full

          end if;

          sampst <= CHA_SYNC;

        when others =>

          sampst <= IDLE;

      end case;

    end if;

  end process SAEX;

-- determine sample resolution from mode bits in 32bit mode

  M32: if DATA_WIDTH = 32 generate

    samp_start <= 8 when conf_mode = "0000" else

                  7 when conf_mode = "0001" else

                  6 when conf_mode = "0010" else

                  5 when conf_mode = "0011" else

                  4 when conf_mode = "0100" else

                  3 when conf_mode = "0101" else

                  2 when conf_mode = "0110" else

                  1 when conf_mode = "0111" else

                  8;

  end generate M32;

-- in 16bit mode onyl 16bit of audio is supported 

  M16: if DATA_WIDTH = 16 generate

    samp_start <= 8;

  end generate M16;

end rtl;