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

--

-- (C) Copyright 2017 DFC Design, s.r.o., Brno, Czech Republic

-- Author: Marek Kvas (m.kvas@dfcdesign.cz)

--

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

-- This file is part of UDP/IPv4 for 10 G Ethernet core.

-- 

-- UDP/IPv4 for 10 G Ethernet core 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 3 of the License, or

-- (at your option) any later version.

-- 

-- UDP/IPv4 for 10 G Ethernet core 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 UDP/IPv4 for 10 G Ethernet core.  If not, 

-- see <http://www.gnu.org/licenses/>.

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

--

-- This module adapts TX interface of frame_gen module to be closer to

-- the one used by RX path. It adds FIFO to TX data path so users don't

-- have to provide data in each cycle and length doesn't have to be known

-- in advance.

--

--

-- Two FIFOs are used. One to store data from user, the other one to store

-- tags currently consisting of length of frame to be sent only.

-- FIFOs are placed outside this module. They must be FWFT.

--

-- It is aimed to be used together with frame_gen_fifo_if that sits on the 

-- other side of FIFOs and interfaces them to the frame_gen module.

--

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

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

library work;

use work.frame_pkg.all;

Library UNISIM;

use UNISIM.vcomponents.all;

entity frame_tx_if is

   port (

      CLK            : in  std_logic;

      RST            : in  std_logic;

      DST_MAC        : in  mac_addr_type;

      DST_IP         : in  ip_addr_type;

      SRC_UDP        : in  udp_port_type;

      DST_UDP        : in  udp_port_type;

      FRAME_VALID    : in  std_logic;

      FRAME_RDY      : out std_logic;

      FRAME_LAST     : in  std_logic;

      FRAME_BE       : in  std_logic_vector(7 downto 0);

      FRAME_DATA     : in  data64_port_type;

      -- Tag and data fifos

      DFIFO_DATA     : out txi_dfifo_data_type;

      DFIFO_WR_EN    : out std_logic;

      DFIFO_FULL     : in  std_logic;

      TFIFO_DATA     : out txi_tfifo_data_type;

      TFIFO_WR_EN    : out std_logic;

      TFIFO_FULL     : in  std_logic

        );

end entity;

architecture synthesis of frame_tx_if is

   type in_fsm_type is (I_IDLE_DI0, I_DI1, I_DATA, I_TAG);

   signal in_fsm_cur    : in_fsm_type;

   signal in_fsm_next   : in_fsm_type;

   signal frame_rdy_i   : std_logic;

   signal dfifo_wr_en_i : std_logic;

   signal tfifo_wr_en_i : std_logic;

   signal length_cnt_en : std_logic;

   signal length_cnt    : unsigned(txi_tfifo_data_type'length - 1 downto 0);

begin

   -- FSM controlling insertion of data into FIFOs

   in_fsm_adv_proc : process(CLK)

   begin

      if rising_edge(CLK) then

         if RST = '1' then

            in_fsm_cur <= I_IDLE_DI0;

         else

            in_fsm_cur <= in_fsm_next;

         end if;

      end if;

   end process;

   in_fsm_trans_out_proc : process(in_fsm_cur, DFIFO_FULL, TFIFO_FULL,

                              DST_MAC, DST_UDP, DST_IP, SRC_UDP,

                              FRAME_VALID, FRAME_LAST, FRAME_BE, FRAME_DATA)

   begin

      in_fsm_next <= in_fsm_cur;

      frame_rdy_i <= not DFIFO_FULL;

      dfifo_wr_en_i <= '0';

      tfifo_wr_en_i <= '0';

      DFIFO_DATA <= FRAME_BE & FRAME_DATA;

      length_cnt_en <= '0';

      case in_fsm_cur is

         when I_IDLE_DI0 =>

            frame_rdy_i <= '0';

            DFIFO_DATA <= x"000000" & DST_IP & SRC_UDP;

            if FRAME_VALID = '1' and DFIFO_FULL = '0' then

               in_fsm_next <= I_DI1;

               dfifo_wr_en_i <= '1';

            end if;

         when I_DI1 =>

            frame_rdy_i <= '0';

            DFIFO_DATA <= x"00" & DST_MAC & DST_UDP;

            if DFIFO_FULL = '0' then

               in_fsm_next <= I_DATA;

               dfifo_wr_en_i <= '1';

            end if;

         when I_DATA =>

            length_cnt_en <= '1';

            -- In case of empty packet this inserts empty word into the fifo

            -- frame_gen_fifo_if is responsible for discarding it

            dfifo_wr_en_i <= not DFIFO_FULL and FRAME_VALID;

            if FRAME_LAST = '1' and FRAME_VALID = '1' and DFIFO_FULL = '0' then

               in_fsm_next <= I_TAG;

            end if;

         when I_TAG =>

            frame_rdy_i <= '0';

            if TFIFO_FULL = '0' then

               tfifo_wr_en_i <= '1';

               in_fsm_next <= I_IDLE_DI0;

            end if;

         when others =>

            in_fsm_next <= I_TAG;

      end case;

   end process;

   -- Count written bytes to determine length;

   length_proc : process(CLK)

   begin

      if rising_edge(CLK) then

         if length_cnt_en  = '1' then

            if dfifo_wr_en_i = '1' then

               if FRAME_LAST = '0' then

                  length_cnt <= length_cnt + 8;

               else

                  case (FRAME_BE) is

                     when "11111111" => length_cnt <= length_cnt + 8;

                     when "01111111" => length_cnt <= length_cnt + 7;

                     when "00111111" => length_cnt <= length_cnt + 6;

                     when "00011111" => length_cnt <= length_cnt + 5;

                     when "00001111" => length_cnt <= length_cnt + 4;

                     when "00000111" => length_cnt <= length_cnt + 3;

                     when "00000011" => length_cnt <= length_cnt + 2;

                     when "00000001" => length_cnt <= length_cnt + 1;

                     when "00000000" => length_cnt <= length_cnt + 0;

                     when others => length_cnt <= length_cnt + 8;

                  end case;

               end if;

            end if;

         else

            length_cnt <= (others => '0');

         end if;

      end if;

   end process;

   FRAME_RDY <= frame_rdy_i;

   DFIFO_WR_EN <= dfifo_wr_en_i;

   TFIFO_WR_EN <= tfifo_wr_en_i;

   TFIFO_DATA <= std_logic_vector(length_cnt);

end architecture;