wb_clk_i => wb_clk_o,
      wb_rst_i => wb_rst_o,
      wb_sel_i => wb_sel_o,
      wb_stb_i => wb_stb_32bit_tx2,
      wb_we_i => wb_we_o,
      wb_cyc_i => wb_cyc_o,
      wb_bte_i => wb_bte_o,
      wb_cti_i => wb_cti_o,
      wb_adr_i => wb_adr_o(5 downto 0),
      wb_dat_i => wb_dat_o(31 downto 0),
      wb_ack_o => tx2_ack,
      wb_dat_o => tx2_dat_i,
      tx_int_o => tx2_int_o,
      i2s_sd_o => i2s_sd2,
      i2s_sck_o => i2s_sck2,
      i2s_ws_o => i2s_ws2);

-- I2S receiver 1, master mode
  IRX32M: rx_i2s_topm 
    generic map (DATA_WIDTH => 32,
                 ADDR_WIDTH => 6)
    port map (
      -- Wishbone interface
      wb_clk_i => wb_clk_o,
      wb_rst_i => wb_rst_o,
      wb_sel_i => wb_sel_o,
      wb_stb_i => wb_stb_32bit_rx1,
      wb_we_i => wb_we_o,
      wb_cyc_i => wb_cyc_o,
      wb_bte_i => wb_bte_o,
      wb_cti_i => wb_cti_o,
      wb_adr_i => wb_adr_o(5 downto 0),
      wb_dat_i => wb_dat_o(31 downto 0),
      i2s_sd_i => i2s_sd1,
      wb_ack_o => rx1_ack,
      wb_dat_o => rx1_dat_i,
      rx_int_o => rx1_int_o,
      i2s_sck_o => i2s_sck1,
      i2s_ws_o => i2s_ws1);

-- I2S receiver 2, slave mode
  IRX32S: rx_i2s_tops 
    generic map (DATA_WIDTH => 32,
                 ADDR_WIDTH => 6)
    port map (
      -- Wishbone interface
      wb_clk_i => wb_clk_o,
      wb_rst_i => wb_rst_o,
      wb_sel_i => wb_sel_o,
      wb_stb_i => wb_stb_32bit_rx2,
      wb_we_i => wb_we_o,
      wb_cyc_i => wb_cyc_o,
      wb_bte_i => wb_bte_o,
      wb_cti_i => wb_cti_o,
      wb_adr_i => wb_adr_o(5 downto 0),
      wb_dat_i => wb_dat_o(31 downto 0),
      i2s_sd_i => i2s_sd2,
      i2s_sck_i => i2s_sck2,
      i2s_ws_i => i2s_ws2,
      wb_ack_o => rx2_ack,
      wb_dat_o => rx2_dat_i,
      rx_int_o => rx2_int_o);
  
-- Main test process
  MAIN: process
    variable read_32bit : std_logic_vector(31 downto 0);
    variable idx : integer;

    -- Make simplified versions of procedures in wb_tb_pack
    procedure wb_write_32 (
      constant ADDRESS: in natural; 
      constant DATA: in natural) is 
    begin
      wb_write(ADDRESS, DATA, wb_adr_o, wb_dat_o(31 downto 0), wb_cyc_o,
               wb_sel_o, wb_we_o, wb_clk_o, wb_ack_i);
    end;
    
    procedure wb_check_32 (
      constant ADDRESS: in natural;
      constant EXP_DATA : in natural) is
    begin
      wb_check(ADDRESS, EXP_DATA, wb_adr_o, wb_dat_i(31 downto 0), wb_cyc_o,
               wb_sel_o, wb_we_o, wb_clk_o, wb_ack_i);
    end;
    
    procedure wb_read_32 (
      constant ADDRESS: in natural) is
    begin 
      wb_read(ADDRESS, read_32bit, wb_adr_o, wb_dat_i(31 downto 0), wb_cyc_o,
              wb_sel_o, wb_we_o, wb_clk_o, wb_ack_i);
    end;
    
  begin
    message("Simulation start with system reset.");
    wb_rst_o <= '1'; -- system reset
    wb_sel_o <= '0';
    wb_stb_o <= '0';
    wb_sel_o <= '0';
    wb_we_o <= '0';
    wb_cyc_o <= '0';
    wb_bte_o <= "00";
    wb_cti_o <= "000";
    wb_adr_o <= (others => '0');
    wb_dat_o <= (others => '0');
    wait for 200 ns;
    wb_rst_o <= '0';    
    message("Check receiver version registers:");
    wb_check_32(RX1_VERSION, 16#000001b1#);
    wb_check_32(RX2_VERSION, 16#00000191#);
    message("Check transmitter version registers:");
    wb_check_32(TX1_VERSION, 16#00000191#);
    wb_check_32(TX2_VERSION, 16#000001b1#);
    message("Fill up sample buffers with test signal, ");
    message("ramp up in left, ramp down in right:");
    SGEN: for i in 0 to 15 loop
      wb_write_32(TX1_BUF_BASE + 2*i, (32768 + i*497)*256);  -- left
      wb_write_32(TX1_BUF_BASE + 2*i + 1, (32767 - i*497)*256);  -- right
      wb_write_32(TX2_BUF_BASE + 2*i, (32767 - i*497)*16);  -- left
      wb_write_32(TX2_BUF_BASE + 2*i + 1, (32768 + i*497)*16);  --right
    end loop;
     message("*** Test of master TX and slave RX ***");
    message("Enable transmitter 2:");
    wb_write_32(TX2_INTMASK, 16#00000003#);  -- enable interrupts
    wb_write_32(TX2_CONFIG, 16#00140703#);  -- 20bit resolution
    message("Enable recevier 2:");
    wb_write_32(RX2_INTMASK, 16#00000003#);  -- enable interrupts
    wb_write_32(RX2_CONFIG, 16#00180003#);  -- 24bit resolution
    wait_for_event("Wait for transmitter 2 LSBF interrupt", 150 us, tx2_int_o);
    wait_for_event("Wait for recevier 2 LSBF interrupt", 150 us, rx2_int_o);
    message("Clear transmitter LSBF interrupt:");
    wb_write_32(TX2_INTSTAT, 16#00000001#);
    wb_check_32(TX2_INTSTAT, 16#00000000#);
    signal_check("tx2_int_o", '0', tx2_int_o);
    message("Clear receiver LSBF interrupt:");
    wb_write_32(RX2_INTSTAT, 16#00000001#);
    wb_check_32(RX2_INTSTAT, 16#00000000#);
    signal_check("rx2_int_o", '0', rx2_int_o);
    message("Check received data, lower sample buffer:");
    wb_read_32(RX2_BUF_BASE);
    -- calculate which index this word was generated with
    idx := (32767 - to_integer(unsigned(read_32bit(31 downto 8)))) / 497;
    -- then check for correct values
    CHKL: for i in 0 to 7 - idx loop
      wb_check_32(RX2_BUF_BASE + 2*i, (32767 - (i+idx)*497)*256);
      wb_check_32(RX2_BUF_BASE + 2*i + 1, (32768 + (i+idx)*497)*256);
    end loop;
    wait_for_event("Wait for transmitter 2 HSBF interrupt", 150 us, tx2_int_o);
    wait_for_event("Wait for recevier 2 HSBF interrupt", 150 us, rx2_int_o);
    message("Clear transmitter HSBF interrupt:");
    wb_write_32(TX2_INTSTAT, 16#00000002#);
    wb_check_32(TX2_INTSTAT, 16#00000000#);
    signal_check("tx2_int_o", '0', tx2_int_o);
    message("Clear receiver HSBF interrupt:");
    wb_write_32(RX2_INTSTAT, 16#00000002#);
    wb_check_32(RX2_INTSTAT, 16#00000000#);
    signal_check("rx2_int_o", '0', rx2_int_o);
    message("Check received data, upper sample buffer:");
    CHKH: for i in 8 - idx to 15 - idx loop
      wb_check_32(RX2_BUF_BASE + 2*i, (32767 - (i+idx)*497)*256);
      wb_check_32(RX2_BUF_BASE + 2*i + 1, (32768 + (i+idx)*497)*256);
    end loop;

    message("*** Test of slave TX and master RX ***");
    message("Enable transmitter 1:");
    wb_write_32(TX1_INTMASK, 16#00000003#);  -- enable interrupts
    wb_write_32(TX1_CONFIG, 16#00180007#);  -- 24bit resolution
    message("Enable recevier 1:");
    wb_write_32(RX1_INTMASK, 16#00000003#);  -- enable interrupts
    wb_write_32(RX1_CONFIG, 16#00100707#);  -- 16bit resolution          
    wait_for_event("Wait for transmitter 1 LSBF interrupt", 150 us, tx1_int_o);
    message("Clear LSBF interrupt:");
    wb_write_32(TX1_INTSTAT, 16#00000001#);
    wb_check_32(TX1_INTSTAT, 16#00000000#);
    signal_check("tx1_int_o", '0', tx1_int_o);
    wait_for_event("Wait for recevier 1 LSBF interrupt", 150 us, rx1_int_o);
    message("Clear LSBF interrupt:");
    wb_write_32(RX1_INTSTAT, 16#00000001#);
    wb_check_32(RX1_INTSTAT, 16#00000000#);
    signal_check("rx1_int_o", '0', rx1_int_o);
    message("Check received data (#1), lower sample buffer:");
    wb_read_32(RX1_BUF_BASE);
    -- calculate which index this word was generated with
    idx := (32767 - to_integer(unsigned(read_32bit(15 downto 0)))) / 497;
    -- then check for correct values
    CHKL1: for i in 0 to 7 - idx loop
      wb_check_32(RX1_BUF_BASE + 2*i, 32768 + (i+idx)*497);
      wb_check_32(RX1_BUF_BASE + 2*i + 1, 32767 - (i+idx)*497);
    end loop;
    wait_for_event("Wait for transmitter 1 HSBF interrupt", 150 us, tx1_int_o);
    message("Clear HSBF interrupt:");
    wb_write_32(TX1_INTSTAT, 16#00000002#);
    wb_check_32(TX1_INTSTAT, 16#00000000#);
    signal_check("tx1_int_o", '0', tx1_int_o);
    wait_for_event("Wait for recevier 1 HSBF interrupt", 150 us, rx1_int_o);
    message("Clear HSBF interrupt:");
    wb_write_32(RX1_INTSTAT, 16#00000002#);
    wb_check_32(RX1_INTSTAT, 16#00000000#);
    signal_check("rx1_int_o", '0', rx1_int_o);
    message("Check received data (#1), higher sample buffer:");
    CHKH1: for i in 8 - idx to 15 - idx loop
      wb_check_32(RX1_BUF_BASE + 2*i, 32768 + (i+idx)*497);
      wb_check_32(RX1_BUF_BASE + 2*i + 1, 32767 - (i+idx)*497);
    end loop;
    
    sim_report("");
    report "End of simulation! (ignore this failure)"
      severity failure;
    wait;
  end process MAIN;
  
-- Bus strobe generator based on address. 32bit recevier mapped to addr. 0x1000
-- 32bit transmitter mapped to address 0x2000
  wb_stb_32bit_rx1 <= '1' when wb_adr_o(15 downto 12) = "0001" else '0';
  wb_stb_32bit_tx1 <= '1' when wb_adr_o(15 downto 12) = "0010" else '0';
  wb_stb_32bit_rx2 <= '1' when wb_adr_o(15 downto 12) = "0011" else '0';
  wb_stb_32bit_tx2 <= '1' when wb_adr_o(15 downto 12) = "0100" else '0';
  
-- Clock process, 50Mhz Wishbone master freq.
  CLKGEN: process
  begin
    wb_clk_o <= '0';
    wait for 10 ns;
    wb_clk_o <= '1';
    wait for 10 ns;
  end process CLKGEN;
  
end behav;