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--------------------------------------------------------------------------------
-- Description:
-- This is an example testbench for the Fast Fourier Transform IP core.
-- The testbench has been generated by Vivado to accompany the IP core
-- instance you have generated.
--
-- This testbench is for demonstration purposes only.  See note below for
-- instructions on how to use it with your core.
--
-- See the Fast Fourier Transform product guide for further information
-- about this core.
--
--------------------------------------------------------------------------------
-- Using this testbench
--
-- This testbench instantiates your generated Fast Fourier Transform core
-- instance named "xfft_0".
--
-- Use Vivado's Run Simulation flow to run this testbench.  See the Vivado
-- documentation for details.
--------------------------------------------------------------------------------

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

entity tb_xfft_0 is
end tb_xfft_0;

architecture tb of tb_xfft_0 is

  -----------------------------------------------------------------------
  -- Timing constants
  -----------------------------------------------------------------------
  constant CLOCK_PERIOD : time := 100 ns;
  constant T_HOLD       : time := 10 ns;
  constant T_STROBE     : time := CLOCK_PERIOD - (1 ns);

  -----------------------------------------------------------------------
  -- DUT signals
  -----------------------------------------------------------------------

  -- General signals
  signal aclk                        : std_logic := '0';  -- the master clock

  -- Config slave channel signals
  signal s_axis_config_tvalid        : std_logic := '0';  -- payload is valid
  signal s_axis_config_tready        : std_logic := '1';  -- slave is ready
  signal s_axis_config_tdata         : std_logic_vector(15 downto 0) := (others => '0');  -- data payload

  -- Data slave channel signals
  signal s_axis_data_tvalid          : std_logic := '0';  -- payload is valid
  signal s_axis_data_tready          : std_logic := '1';  -- slave is ready
  signal s_axis_data_tdata           : std_logic_vector(31 downto 0) := (others => '0');  -- data payload
  signal s_axis_data_tlast           : std_logic := '0';  -- indicates end of packet

  -- Data master channel signals
  signal m_axis_data_tvalid          : std_logic := '0';  -- payload is valid
  signal m_axis_data_tready          : std_logic := '1';  -- slave is ready
  signal m_axis_data_tdata           : std_logic_vector(31 downto 0) := (others => '0');  -- data payload
  signal m_axis_data_tlast           : std_logic := '0';  -- indicates end of packet

  -- Event signals
  signal event_frame_started         : std_logic := '0';
  signal event_tlast_unexpected      : std_logic := '0';
  signal event_tlast_missing         : std_logic := '0';
  signal event_status_channel_halt   : std_logic := '0';
  signal event_data_in_channel_halt  : std_logic := '0';
  signal event_data_out_channel_halt : std_logic := '0';

  -----------------------------------------------------------------------
  -- Aliases for AXI channel TDATA and TUSER fields
  -- These are a convenience for viewing data in a simulator waveform viewer.
  -- If using ModelSim or Questa, add "-voptargs=+acc=n" to the vsim command
  -- to prevent the simulator optimizing away these signals.
  -----------------------------------------------------------------------

  -- Config slave channel alias signals
  signal s_axis_config_tdata_fwd_inv      : std_logic                    := '0';              -- forward or inverse
  signal s_axis_config_tdata_scale_sch    : std_logic_vector(9 downto 0) := (others => '0');  -- scaling schedule

  -- Data slave channel alias signals
  signal s_axis_data_tdata_re             : std_logic_vector(15 downto 0) := (others => '0');  -- real data
  signal s_axis_data_tdata_im             : std_logic_vector(15 downto 0) := (others => '0');  -- imaginary data

  -- Data master channel alias signals
  signal m_axis_data_tdata_re             : std_logic_vector(15 downto 0) := (others => '0');  -- real data
  signal m_axis_data_tdata_im             : std_logic_vector(15 downto 0) := (others => '0');  -- imaginary data

  -----------------------------------------------------------------------
  -- Constants, types and functions to create input data
  -----------------------------------------------------------------------

  constant IP_WIDTH    : integer := 16;
  constant MAX_SAMPLES : integer := 2**10;  -- maximum number of samples in a frame
  type T_IP_SAMPLE is record
    re : std_logic_vector(IP_WIDTH-1 downto 0);
    im : std_logic_vector(IP_WIDTH-1 downto 0);
  end record;
  type T_IP_TABLE is array (0 to MAX_SAMPLES-1) of T_IP_SAMPLE;

  -- Zeroed input data table, for reset and initialization
  constant IP_TABLE_CLEAR : T_IP_TABLE := (others => (re => (others => '0'),
                                                      im => (others => '0')));

  -- Function to generate input data table
  -- Data is a complex sinusoid exp(-jwt) with a frequency 2.6 times the frame size
  -- added to another with a lower magnitude and a higher frequency
  function create_ip_table return T_IP_TABLE is
    variable result : T_IP_TABLE;
    variable theta  : real;
    variable theta2 : real;
    variable re_real : real;
    variable im_real : real;
    variable re_int : integer;
    variable im_int : integer;
    constant DATA_WIDTH : integer := 14;
  begin
    for i in 0 to MAX_SAMPLES-1 loop
      theta   := real(i) / real(MAX_SAMPLES) * 2.6 * 2.0 * MATH_PI;
      re_real := cos(-theta);
      im_real := sin(-theta);
      theta2  := real(i) / real(MAX_SAMPLES) * 23.2 * 2.0 * MATH_PI;
      re_real := re_real + (cos(-theta2) / 4.0);
      im_real := im_real + (sin(-theta2) / 4.0);
      re_int  := integer(round(re_real * real(2**(DATA_WIDTH))));
      im_int  := integer(round(im_real * real(2**(DATA_WIDTH))));
      result(i).re := std_logic_vector(to_signed(re_int, IP_WIDTH));
      result(i).im := std_logic_vector(to_signed(im_int, IP_WIDTH));
    end loop;
    return result;
  end function create_ip_table;

  -- Call the function to create the input data
  constant IP_DATA : T_IP_TABLE := create_ip_table;

  -----------------------------------------------------------------------
  -- Testbench signals
  -----------------------------------------------------------------------

  -- Communication between processes regarding DUT configuration
  type T_DO_CONFIG is (NONE, IMMEDIATE, AFTER_START, DONE);
  shared variable do_config : T_DO_CONFIG := NONE;  -- instruction for driving config slave channel
  type T_CFG_FWD_INV is (FWD, INV);
  signal cfg_fwd_inv : T_CFG_FWD_INV := FWD;
  type T_CFG_SCALE_SCH is (ZERO, DEFAULT);
  signal cfg_scale_sch : T_CFG_SCALE_SCH := DEFAULT;

  -- Recording output data, for reuse as input data
  signal op_sample       : integer    := 0;    -- output sample number
  signal op_sample_first : std_logic  := '1';  -- indicates first output sample of a frame
  signal ip_frame        : integer    := 0;    -- input / configuration frame number
  signal op_data         : T_IP_TABLE := IP_TABLE_CLEAR;  -- recorded output data
  signal op_frame        : integer    := 0;    -- output frame number (incremented at end of frame output)


begin

  -----------------------------------------------------------------------
  -- Instantiate the DUT
  -----------------------------------------------------------------------

  dut : entity work.xfft_0
    port map (
      aclk                        => aclk,
      s_axis_config_tvalid        => s_axis_config_tvalid,
      s_axis_config_tready        => s_axis_config_tready,
      s_axis_config_tdata         => s_axis_config_tdata,
      s_axis_data_tvalid          => s_axis_data_tvalid,
      s_axis_data_tready          => s_axis_data_tready,
      s_axis_data_tdata           => s_axis_data_tdata,
      s_axis_data_tlast           => s_axis_data_tlast,
      m_axis_data_tvalid          => m_axis_data_tvalid,
      m_axis_data_tready          => m_axis_data_tready,
      m_axis_data_tdata           => m_axis_data_tdata,
      m_axis_data_tlast           => m_axis_data_tlast,
      event_frame_started         => event_frame_started,
      event_tlast_unexpected      => event_tlast_unexpected,
      event_tlast_missing         => event_tlast_missing,
      event_status_channel_halt   => event_status_channel_halt,
      event_data_in_channel_halt  => event_data_in_channel_halt,
      event_data_out_channel_halt => event_data_out_channel_halt
      );

  -----------------------------------------------------------------------
  -- Generate clock
  -----------------------------------------------------------------------

  clock_gen : process
  begin
    aclk <= '0';
    wait for CLOCK_PERIOD;
    loop
      aclk <= '0';
      wait for CLOCK_PERIOD/2;
      aclk <= '1';
      wait for CLOCK_PERIOD/2;
    end loop;
  end process clock_gen;

  -----------------------------------------------------------------------
  -- Generate data slave channel inputs
  -----------------------------------------------------------------------

  data_stimuli : process

    -- Variables for random number generation
    variable seed1, seed2 : positive;
    variable rand         : real;

    -- Procedure to drive an input sample with specific data
    -- data is the data value to drive on the tdata signal
    -- last is the bit value to drive on the tlast signal
    -- valid_mode defines how to drive TVALID: 0 = TVALID always high, 1 = TVALID low occasionally
    procedure drive_sample ( data       : std_logic_vector(31 downto 0);
                             last       : std_logic;
                             valid_mode : integer := 0 ) is
    begin
      s_axis_data_tdata  <= data;
      s_axis_data_tlast  <= last;

      if valid_mode = 1 then
        uniform(seed1, seed2, rand);  -- generate random number
        if rand < 0.25 then
          s_axis_data_tvalid <= '0';
          uniform(seed1, seed2, rand);  -- generate another random number
          wait for CLOCK_PERIOD * integer(round(rand * 4.0));  -- hold TVALID low for up to 4 cycles
          s_axis_data_tvalid <= '1';  -- now assert TVALID
        else
          s_axis_data_tvalid <= '1';
        end if;
      else
        s_axis_data_tvalid <= '1';
      end if;
      loop
        wait until rising_edge(aclk);
        exit when s_axis_data_tready = '1';
      end loop;
      wait for T_HOLD;
      s_axis_data_tvalid <= '0';
    end procedure drive_sample;

    -- Procedure to drive an input frame with a table of data
    -- data is the data table containing input data
    -- valid_mode defines how to drive TVALID: 0 = TVALID always high, 1 = TVALID low occasionally
    procedure drive_frame ( data         : T_IP_TABLE;
                            valid_mode   : integer := 0 ) is
      variable samples : integer;
      variable index   : integer;
      variable sample_data : std_logic_vector(31 downto 0);
      variable sample_last : std_logic;
    begin
      samples := data'length;
      index  := 0;
      while index < data'length loop
        -- Look up sample data in data table, construct TDATA value
        sample_data(15 downto 0)  := data(index).re;                  -- real data
        sample_data(31 downto 16) := data(index).im;                  -- imaginary data
        -- Construct TLAST's value
        index := index + 1;
        if index >= data'length then
          sample_last := '1';
        else
          sample_last := '0';
        end if;
        -- Drive the sample
        drive_sample(sample_data, sample_last, valid_mode);
      end loop;
    end procedure drive_frame;

    variable op_data_saved : T_IP_TABLE;  -- to save a copy of recorded output data


  begin

    -- Drive inputs T_HOLD time after rising edge of clock
    wait until rising_edge(aclk);
    wait for T_HOLD;

    -- Drive a frame of input data
    ip_frame <= 1;
    drive_frame(IP_DATA);

    -- Allow the result to emerge
    wait until m_axis_data_tlast = '1';
    wait until rising_edge(aclk);
    wait for T_HOLD;

    -- Take a copy of the result, to use later as input
    op_data_saved := op_data;

    -- Now perform an inverse transform on the result to get back to the original input
    -- Set up the configuration (config_stimuli process handles the config slave channel)
    ip_frame <= 2;
    cfg_fwd_inv <= INV;
    do_config := IMMEDIATE;
    while do_config /= DONE loop
      wait until rising_edge(aclk);
    end loop;
    wait for T_HOLD;

    -- Configuration is done.  Set up another configuration to return to forward transforms,
    -- and make the configuration occur as soon as the next frame has begun
    ip_frame <= 3;
    cfg_fwd_inv <= FWD;
    do_config := AFTER_START;

    -- Now drive the input data, using the output data of the last frame
    drive_frame(op_data);
    wait until m_axis_data_tlast = '1';
    wait until rising_edge(aclk);
    wait for T_HOLD;

    -- The frame is complete, and the configuration to forward transforms has already been done,
    -- so drive the input data, using the output data of the last frame,
    -- which is the same as the original input (excepting scaling and finite precision effects).
    -- This time, deassert the data slave channel TVALID occasionally to illustrate AXI handshaking effects:
    -- as the core is configured to use Non Real Time throttle scheme, it will pause when TVALID is low.
    drive_frame(op_data, 1);

    -- During the output of this frame, deassert the data master channel TREADY occasionally:
    -- as the core is configured to use Non Real Time throttle scheme, it will pause when TREADY is low.
    wait until m_axis_data_tvalid = '1';
    wait until rising_edge(aclk);
    while m_axis_data_tlast /= '1' loop
      wait for T_HOLD;
      uniform(seed1, seed2, rand);  -- generate random number
      if rand < 0.25 then
        m_axis_data_tready <= '0';
      else
        m_axis_data_tready <= '1';
      end if;
      wait until rising_edge(aclk);
    end loop;
    wait for T_HOLD;
    m_axis_data_tready <= '1';
    wait for CLOCK_PERIOD;

    -- Now run 4 back-to-back transforms, as quickly as possible.
    -- First queue up 2 configurations: these will be applied successively over the next 2 transforms.
    -- 1st configuration
    ip_frame <= 4;
    cfg_fwd_inv <= FWD;  -- forward transform
    cfg_scale_sch <= DEFAULT;  -- default scaling schedule
    do_config := IMMEDIATE;
    while do_config /= DONE loop
      wait until rising_edge(aclk);
    end loop;
    wait for T_HOLD;

    -- 2nd configuration: same as 1st, except:
    ip_frame <= 5;
    cfg_fwd_inv <= INV;  -- inverse transform
    cfg_scale_sch <= ZERO;  -- no scaling
    do_config := IMMEDIATE;
    while do_config /= DONE loop
      wait until rising_edge(aclk);
    end loop;
    wait for T_HOLD;

    -- Drive the 1st data frame
    drive_frame(IP_DATA);

    -- Request a 3rd configuration, to be sent after 2nd data frame starts
    ip_frame <= 6;
    cfg_fwd_inv <= FWD;  -- forward transform
    cfg_scale_sch <= ZERO;  -- no scaling
    do_config := AFTER_START;

    -- Drive the 2nd data frame
    drive_frame(op_data_saved);

    -- Request a 4th configuration, to be sent after 3rd data frame starts: same as 3rd, except:
    ip_frame <= 7;
    cfg_fwd_inv <= INV;  -- inverse transform
    cfg_scale_sch <= DEFAULT;  -- default scaling schedule
    do_config := AFTER_START;

    -- Drive the 3rd data frame
    drive_frame(IP_DATA);

    -- Drive the 4th data frame
    drive_frame(op_data_saved);

    -- Wait until all the output data from all frames has been produced
    wait until op_frame = 7;
    wait for CLOCK_PERIOD * 10;

    -- End of test
    report "Not a real failure. Simulation finished successfully. Test completed successfully" severity failure;
    wait;

  end process data_stimuli;

  -----------------------------------------------------------------------
  -- Generate config slave channel inputs
  -----------------------------------------------------------------------

  config_stimuli : process
    variable scale_sch : std_logic_vector(9 downto 0);
  begin

    -- Drive a configuration when requested by data_stimuli process
    wait until rising_edge(aclk);
    while do_config = NONE or do_config = DONE loop
      wait until rising_edge(aclk);
    end loop;

    -- If the configuration is requested to occur after the next frame starts, wait for that event
    if do_config = AFTER_START then
      wait until event_frame_started = '1';
      wait until rising_edge(aclk);
    end if;

    -- Drive inputs T_HOLD time after rising edge of clock
    wait for T_HOLD;

    -- Construct the config slave channel TDATA signal
    s_axis_config_tdata <= (others => '0');  -- clear unused bits
    -- Format the transform direction
    if cfg_fwd_inv = FWD then
      s_axis_config_tdata(0) <= '1';  -- forward
    elsif cfg_fwd_inv = INV then
      s_axis_config_tdata(0) <= '0';  -- inverse
    end if;
    -- Format the scaling schedule
    if cfg_scale_sch = ZERO then  -- no scaling
      scale_sch := (others => '0');
    elsif cfg_scale_sch = DEFAULT then  -- default scaling, for largest magnitude output with no overflow guaranteed
      scale_sch(1 downto 0) := "11";  -- largest scaling at first stage
      for s in 2 to 5 loop
        scale_sch(s*2-1 downto s*2-2) := "10";  -- less scaling at later stages
      end loop;
    end if;
    s_axis_config_tdata(10 downto 1) <= scale_sch;

    -- Drive the transaction on the config slave channel
    s_axis_config_tvalid <= '1';
    loop
      wait until rising_edge(aclk);
      exit when s_axis_config_tready = '1';
    end loop;
    wait for T_HOLD;
    s_axis_config_tvalid <= '0';

    -- Tell the data_stimuli process that the configuration has been done
    do_config := DONE;

  end process config_stimuli;

  -----------------------------------------------------------------------
  -- Record outputs, to use later as inputs for another frame
  -----------------------------------------------------------------------

  record_outputs : process (aclk)
    -- Function to digit-reverse an integer, to convert output to input ordering
    function digit_reverse_int ( fwd, width : integer ) return integer is
      variable rev     : integer;
      variable fwd_slv : std_logic_vector(width-1 downto 0);
      variable rev_slv : std_logic_vector(width-1 downto 0);
    begin
      fwd_slv := std_logic_vector(to_unsigned(fwd, width));
      for i in 0 to width/2-1 loop  -- reverse in digit groups (2 bits at a time)
        rev_slv(i*2+1 downto i*2) := fwd_slv(width-i*2-1 downto width-i*2-2);
      end loop;
      if width mod 2 = 1 then  -- width is odd: LSB moves to MSB
        rev_slv(width-1) := fwd_slv(0);
      end if;
      rev := to_integer(unsigned(rev_slv));
      return rev;
    end function digit_reverse_int;

    variable index : integer := 0;

  begin
    if rising_edge(aclk) then
      if m_axis_data_tvalid = '1' and m_axis_data_tready = '1' then
        -- Record output data such that it can be used as input data
        index := op_sample;
        -- Digit-reverse output sample number, to get actual sample index as outputs are in digit-reversed order
        index := digit_reverse_int(index, 10);
        op_data(index).re <= m_axis_data_tdata(15 downto 0);
        op_data(index).im <= m_axis_data_tdata(31 downto 16);
        -- Increment output sample counter
        if m_axis_data_tlast = '1' then  -- end of output frame: reset sample counter and increment frame counter
          op_sample <= 0;
          op_frame <= op_frame + 1;
          op_sample_first <= '1';  -- for next output frame
        else
          op_sample_first <= '0';
          op_sample <= op_sample + 1;
        end if;
      end if;
    end if;
  end process record_outputs;

  -----------------------------------------------------------------------
  -- Check outputs
  -----------------------------------------------------------------------

  check_outputs : process
    variable check_ok : boolean := true;
    -- Previous values of data master channel signals
    variable m_data_tvalid_prev : std_logic := '0';
    variable m_data_tready_prev : std_logic := '0';
    variable m_data_tdata_prev  : std_logic_vector(31 downto 0) := (others => '0');
  begin

    -- Check outputs T_STROBE time after rising edge of clock
    wait until rising_edge(aclk);
    wait for T_STROBE;

    -- Do not check the output payload values, as this requires a numerical model
    -- which would make this demonstration testbench unwieldy.
    -- Instead, check the protocol of the data master channel:
    -- check that the payload is valid (not X) when TVALID is high
    -- and check that the payload does not change while TVALID is high until TREADY goes high

    if m_axis_data_tvalid = '1' then
      if is_x(m_axis_data_tdata) then
        report "ERROR: m_axis_data_tdata is invalid when m_axis_data_tvalid is high" severity error;
        check_ok := false;
      end if;

      if m_data_tvalid_prev = '1' and m_data_tready_prev = '0' then  -- payload must be the same as last cycle
        if m_axis_data_tdata /= m_data_tdata_prev then
          report "ERROR: m_axis_data_tdata changed while m_axis_data_tvalid was high and m_axis_data_tready was low" severity error;
          check_ok := false;
        end if;
      end if;

    end if;

    assert check_ok
      report "ERROR: terminating test with failures." severity failure;

    -- Record payload values for checking next clock cycle
    if check_ok then
      m_data_tvalid_prev  := m_axis_data_tvalid;
      m_data_tready_prev  := m_axis_data_tready;
      m_data_tdata_prev   := m_axis_data_tdata;
    end if;

  end process check_outputs;

  -----------------------------------------------------------------------
  -- Assign TDATA / TUSER fields to aliases, for easy simulator waveform viewing
  -----------------------------------------------------------------------

  -- Config slave channel alias signals
  s_axis_config_tdata_fwd_inv    <= s_axis_config_tdata(0);
  s_axis_config_tdata_scale_sch  <= s_axis_config_tdata(10 downto 1);

  -- Data slave channel alias signals
  s_axis_data_tdata_re           <= s_axis_data_tdata(15 downto 0);
  s_axis_data_tdata_im           <= s_axis_data_tdata(31 downto 16);

  -- Data master channel alias signals
  m_axis_data_tdata_re           <= m_axis_data_tdata(15 downto 0);
  m_axis_data_tdata_im           <= m_axis_data_tdata(31 downto 16);

end tb;