--======================================================================
-- A small back-end emulator for testing purposes.
--======================================================================

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

use work.ipbus.all;
use work.ipbus_reg_types.all;

use work.constants_tcds2.all;
use work.ipbus_decode_backend_emulator.all;
use work.tcds2_streams_pkg.all;

--==================================================

entity backend_emulator is
  generic (
    G_NUM_TTS2_CHANNELS : positive := 1
  );
  port (
    clk_ipb : in std_logic;
    rst_ipb : in std_logic;
    ipb_in  : in ipb_wbus;
    ipb_out : out ipb_rbus;

    clk_40 : in std_logic;

    ttc2_i : in tcds2_ttc2;
    tts2_o : out tcds2_tts2_value_array(G_NUM_TTS2_CHANNELS - 1 downto 0)
  );
end backend_emulator;

--==================================================

architecture arch of backend_emulator is

  -- IPBus read/write buses.
  signal ipbw : ipb_wbus_array(N_SLAVES - 1 downto 0);
  signal ipbr : ipb_rbus_array(N_SLAVES - 1 downto 0);

  -- CSR signals.
  signal ctrl : ipb_reg_v(1 downto 0);
  signal stat : ipb_reg_v(0 downto 0);

  -- TCDS2 TTC2/TTS2 signals.
  signal ttc2 : tcds2_ttc2;
  signal tts2 : tcds2_tts2_value_array(G_NUM_TTS2_CHANNELS - 1 downto 0);

  -- Misc.
  signal is_tts2_forced_tmp : std_logic;
  signal is_tts2_forced     : boolean;

  signal tts2_value       : tcds2_tts2_value;
  signal tts2_force_value : tcds2_tts2_value;

begin

  ------------------------------------------
  -- IPBus address decoder.
  ------------------------------------------

  fabric : entity work.ipbus_fabric_sel
    generic map (
      NSLV      => N_SLAVES,
      SEL_WIDTH => IPBUS_SEL_WIDTH
    )
    port map (
      ipb_in          => ipb_in,
      ipb_out         => ipb_out,
      sel             => ipbus_sel_backend_emulator(ipb_in.ipb_addr),
      ipb_to_slaves   => ipbw,
      ipb_from_slaves => ipbr
    );

  ------------------------------------------
  -- Control and status register.
  ------------------------------------------

  csr : entity work.ipbus_ctrlreg_v
    generic map (
      N_CTRL => ctrl'length,
      N_STAT => stat'length
    )
    port map (
      clk       => clk_ipb,
      reset     => rst_ipb,
      ipbus_in  => ipbw(N_SLV_CSR),
      ipbus_out => ipbr(N_SLV_CSR),
      q         => ctrl,
      d         => stat
    );

  is_tts2_forced_tmp <= ctrl(0)(0);
  tts2_force_value   <= to_integer(unsigned(ctrl(1)(C_TCDS2_TTS2_VALUE_WIDTH - 1 downto 0)));

  -- DEBUG DEBUG DEBUG
  -- Test counter for now.
  stat(0) <= std_logic_vector(resize(unsigned(ttc2.reserved), C_IPBUS_WORD_WIDTH));
  -- DEBUG DEBUG DEBUG end

  is_tts2_forced <= true when is_tts2_forced_tmp = '1'
                    else false;

  ------------------------------------------

  tts2_value <= tts2_force_value when is_tts2_forced
                else C_TCDS2_TTS2_VALUE_READY;
  tts2       <= (0 => tts2_value, others => C_TCDS2_TTS2_VALUE_IGNORED);

  ttc2   <= ttc2_i;
  tts2_o <= tts2;

end arch;

--======================================================================