----------------------------------------------------------------------
----                                                              ----
---- WISHBONE I2S Interface IP Core                               ----
----                                                              ----
---- This file is part of the I2S Interface project               ----
---- http://www.opencores.org/cores/i2s_interface/                ----
----                                                              ----
---- Description                                                  ----
---- I2S receiver Wishbone bus cycle decoder.                     ----
----                                                              ----
---- To Do:                                                       ----
---- -                                                            ----
----                                                              ----
---- Author(s):                                                   ----
---- - Geir Drange, gedra@opencores.org                           ----
----                                                              ----
----------------------------------------------------------------------
----                                                              ----
---- 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 General          ----
---- Public License as published by the Free Software Foundation; ----
---- either version 2.0 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 General Public License for more details.----
----                                                              ----
---- You should have received a copy of the GNU General           ----
---- Public License along with this source; if not, download it   ----
---- from http://www.gnu.org/licenses/gpl.txt                     ----
----                                                              ----
----------------------------------------------------------------------
--
-- CVS Revision History
--
-- $Log: rx_i2s_wbd.vhd,v $
-- Revision 1.3  2005/01/17 17:26:47  gedra
-- Bugfix of register read/write strobes
--
-- Revision 1.2  2004/08/06 18:55:43  gedra
-- De-linting.
--
-- Revision 1.1  2004/08/03 18:50:29  gedra
-- Receiver Wishbone cycle decoder.
--
--
--

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity rx_i2s_wbd is	 
  generic (DATA_WIDTH: integer;
           ADDR_WIDTH: integer);
  port (
    wb_clk_i: in std_logic;             -- wishbone clock
    wb_rst_i: in std_logic;             -- reset signal
    wb_sel_i: in std_logic;             -- select input
    wb_stb_i: in std_logic;             -- strobe input
    wb_we_i: in std_logic;              -- write enable
    wb_cyc_i: in std_logic;             -- cycle input
    wb_bte_i: in std_logic_vector(1 downto 0);  -- burts type extension
    wb_cti_i: in std_logic_vector(2 downto 0);  -- cycle type identifier
    wb_adr_i: in std_logic_vector(ADDR_WIDTH - 1 downto 0);  -- address
    data_out: in std_logic_vector(DATA_WIDTH - 1 downto 0); -- internal bus
    wb_ack_o: out std_logic;            -- acknowledge
    wb_dat_o: out std_logic_vector(DATA_WIDTH - 1 downto 0);  -- data out
    version_rd: out std_logic;          -- Version register read 
    config_rd: out std_logic;           -- Config register read
    config_wr: out std_logic;           -- Config register write
    intmask_rd: out std_logic;          -- Interrupt mask register read
    intmask_wr: out std_logic;          -- Interrupt mask register write
    intstat_rd: out std_logic;          -- Interrupt status register read
    intstat_wr: out std_logic;          -- Interrupt status register read
    mem_rd: out std_logic;              -- Sample memory read
    mem_addr: out std_logic_vector(ADDR_WIDTH - 2 downto 0));  -- memory addr.
end rx_i2s_wbd;

architecture rtl of rx_i2s_wbd is
 
  constant REG_RXVERSION : std_logic_vector(3 downto 0) := "0000";
  constant REG_RXCONFIG  : std_logic_vector(3 downto 0) := "0001";
  constant REG_RXINTMASK : std_logic_vector(3 downto 0) := "0010";
  constant REG_RXINTSTAT : std_logic_vector(3 downto 0) := "0011";
  signal iack, iwr, ird : std_logic;
  signal acnt: integer range 0 to 2**(ADDR_WIDTH - 1) - 1;
  signal all_ones : std_logic_vector(ADDR_WIDTH - 1 downto 0);
  signal rdout : std_logic_vector(DATA_WIDTH - 1 downto 0);
  
begin 

  wb_ack_o <= iack;

-- acknowledge generation
  ACK: process (wb_clk_i, wb_rst_i)
  begin
    if wb_rst_i = '1' then
      iack <= '0';           
    elsif rising_edge(wb_clk_i) then
      if wb_cyc_i = '1' and wb_sel_i = '1' and wb_stb_i = '1' then
        case wb_cti_i is
          when "010" => -- incrementing burst
            case wb_bte_i is -- burst extension
              when "00" => -- linear burst
                iack <= '1';
              when others => -- all other treated assert classic cycle
                iack <= not iack;
            end case;    
          when "111" => -- end of burst
            iack <= not iack;
          when others => -- all other treated assert classic cycle 
            iack <= not iack;
        end case;              
      else
        iack <= '0';
      end if;    
    end if;
  end process ACK;

-- write generation      
  WR: process (wb_clk_i, wb_rst_i)
  begin
    if wb_rst_i = '1' then
      iwr <= '0';     
    elsif rising_edge(wb_clk_i) then
      if wb_cyc_i = '1' and wb_sel_i = '1' and wb_stb_i = '1' and
        wb_we_i = '1' then
        case wb_cti_i is
          when "010" => -- incrementing burst
            case wb_bte_i is -- burst extension
              when "00" => -- linear burst
                iwr <= '1';
              when others => -- all other treated assert classic cycle
                iwr <= not iwr;
            end case;    
          when "111" => -- end of burst
            iwr <= not iwr;
          when others => -- all other treated assert classic cycle   
            iwr <= not iwr;
        end case;
      else
        iwr <= '0';
      end if;        
    end if;   
  end process WR;      

-- read generation
  ird <= '1' when wb_cyc_i = '1' and wb_sel_i = '1' and wb_stb_i = '1' and
         wb_we_i = '0' else '0';

  wb_dat_o <= data_out when wb_adr_i(ADDR_WIDTH - 1) = '1' else rdout;

  DREG: process (wb_clk_i)              -- clock data from registers
  begin 
    if rising_edge(wb_clk_i) then
      rdout <= data_out;
    end if;
  end process DREG;
  
-- sample memory read address. This needs special attention due to read latency
  mem_addr <= std_logic_vector(to_unsigned(acnt, ADDR_WIDTH - 1)) when
              wb_cti_i = "010" and wb_we_i = '0' and iack = '1' and
              wb_bte_i = "00" else wb_adr_i(ADDR_WIDTH - 2 downto 0);
  
  all_ones(ADDR_WIDTH - 1 downto 0) <= (others => '1');
  
  SMA: process (wb_clk_i, wb_rst_i)
  begin               
    if wb_rst_i = '1' then
      acnt <= 0;
    elsif rising_edge(wb_clk_i) then
      if wb_cti_i = "010" and wb_we_i = '0' and wb_bte_i = "00" then      
        if iack = '0' then
          if wb_adr_i = all_ones then
            acnt <= 0;
          else
            acnt <= to_integer(unsigned(wb_adr_i)) + 1;
          end if;
        else
          if acnt < 2**(ADDR_WIDTH - 1) - 1 then
            acnt <= acnt + 1;
          else
            acnt <= 0;
          end if;
        end if;
      end if;
    end if;
  end process SMA;
  
-- read and write strobe generation
  
  version_rd <= '1' when wb_adr_i(3 downto 0) = REG_RXVERSION and ird = '1'
                and wb_adr_i(ADDR_WIDTH - 1) = '0' else '0';
  config_rd <= '1' when wb_adr_i(3 downto 0) = REG_RXCONFIG and ird = '1'
               and wb_adr_i(ADDR_WIDTH - 1) = '0' else '0';
  config_wr <= '1' when wb_adr_i(3 downto 0) = REG_RXCONFIG and iwr = '1'
               and wb_adr_i(ADDR_WIDTH - 1) = '0' else '0';
  intmask_rd <= '1' when wb_adr_i(3 downto 0) = REG_RXINTMASK and ird = '1'
                and wb_adr_i(ADDR_WIDTH - 1) = '0' else '0';
  intmask_wr <= '1' when wb_adr_i(3 downto 0) = REG_RXINTMASK and iwr = '1'
                and wb_adr_i(ADDR_WIDTH - 1) = '0' else '0';
  intstat_rd <= '1' when wb_adr_i(3 downto 0) = REG_RXINTSTAT and ird = '1'
                and wb_adr_i(ADDR_WIDTH - 1) = '0' else '0';
  intstat_wr <= '1' when wb_adr_i(3 downto 0) = REG_RXINTSTAT and iwr = '1'
                and wb_adr_i(ADDR_WIDTH - 1) = '0' else '0';
  mem_rd <= '1' when wb_adr_i(ADDR_WIDTH - 1) = '1' and ird = '1' else '0';
  
end rtl;