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-------------------------------------------------------------------------------
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-- arp3.vhd
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--
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-- Author(s): Jussi Nieminen after Ashley Partis and Jorgen Peddersen
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-- Created: Feb 2001
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-- Last Modified: 2009-09-03
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--
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-- Manages an ARP table for the network stack project. This protocol listens
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-- to incoming data and when an ARP request or reply arrives, the data of the
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-- source is added to the ARP table. The ARP table contains two entries.
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-- When a request arrives a signal is also asserted telling the arp sender to
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-- send an ARP reply when possible. The incoming data from the ethernet layer
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-- is a byte stream.
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-- Licenced under LGPL.
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-------------------------------------------------------------------------------
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library IEEE;
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use IEEE.std_logic_1164.all;
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use IEEE.numeric_std.all;
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use work.udp_ip_pkg.all;
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entity ARP is
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port (
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clk : in std_logic; -- clock signal
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rstn : in std_logic; -- asynchronous active low reset
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new_frame_in : in std_logic; -- from ethernet layer indicates data arrival
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new_word_valid_in : in std_logic; -- indicates a new word in the stream
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frame_re_out : out std_logic;
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frame_data_in : in std_logic_vector (15 downto 0); -- the stream data
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frame_valid_in : in std_logic; -- indicates validity
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frame_len_in : in std_logic_vector( tx_len_w_c-1 downto 0 );
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sending_reply_in : in std_logic; -- ARP sender asserts this when the reply is been transmitted
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req_IP_in : in std_logic_vector (31 downto 0); -- ARP sender can request MACs for this address
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gen_ARP_rep_out : out std_logic; -- tell ARP sender to generate a reply
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gen_ARP_IP_out : out std_logic_vector (31 downto 0); -- destination IP for generated reply
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lookup_MAC_out : out std_logic_vector (47 downto 0); -- if valid, MAC for requested IP
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valid_entry_out : out std_logic; -- indicates if req_IP_in is in table
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done_out : out std_logic
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);
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end ARP;
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architecture ARP_arch of ARP is
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-- State signals and types
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type STATETYPE is (stIdle, stHandleARP, stOperate, stCheckValid);
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signal presState : STATETYPE;
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signal nextState : STATETYPE;
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-- range of 0 to 25 should be enough, but just to be sure..
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signal cnt : integer range 0 to 2**tx_len_w_c-1;
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signal incCnt : std_logic; -- signal to increment cnt
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signal rstCnt : std_logic; -- signal to clear cnt
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signal latchFrameData : std_logic; -- signal to latch stream data
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signal frameData_r : std_logic_vector (15 downto 0); -- register for latched data
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signal shiftSourceIPIn : std_logic; -- signal to shift in source IP
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signal source_IP_r : std_logic_vector (31 downto 0); -- stores source IP
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signal shiftSourceMACIn : std_logic; -- signal to shift in source MAC
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signal source_MAC_r : std_logic_vector (47 downto 0); -- stores source MAC
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signal ARP_operation_r : std_logic; -- '0' for reply, '1' for request
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signal determineOperation : std_logic; -- signal to latch ARP_operation_r from stream
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signal updateARPTable : std_logic; -- this signal updates the ARP table
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signal ARP_entry_IP_r : std_logic_vector (31 downto 0); -- most recent ARP entry IP
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signal ARP_entry_MAC_r : std_logic_vector (47 downto 0); -- most recent ARP entry MAC
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signal ARP_entry_IP_old_r : std_logic_vector (31 downto 0); -- 2nd ARP entry IP
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signal ARP_entry_MAC_old_r : std_logic_vector (47 downto 0); -- 2nd ARP entry MAC
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signal doGenARPRep : std_logic; -- asserted when an ARP reply must be generated
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signal frame_len_r : integer range 0 to 2**tx_len_w_c-1;
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signal frame_invalid_r : std_logic;
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signal frame_invalid : std_logic;
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signal clear_invalid : std_logic;
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-------------------------------------------------------------------------------
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begin
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-------------------------------------------------------------------------------
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process (clk, rstn)
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begin
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if rstn = '0' then -- reset state and ARP entries
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presState <= stIdle;
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ARP_entry_IP_r <= (others => '0');
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ARP_entry_MAC_r <= (others => '0');
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ARP_entry_IP_old_r <= (others => '0');
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ARP_entry_MAC_old_r <= (others => '0');
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frame_re_out <= '0';
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cnt <= 0;
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ARP_operation_r <= '0';
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frameData_r <= (others => '0');
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source_IP_r <= (others => '0');
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source_MAC_r <= (others => '0');
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frame_invalid_r <= '0';
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gen_ARP_rep_out <= '0';
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gen_ARP_IP_out <= (others => '0');
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elsif clk'event and clk = '1' then
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presState <= nextState; -- go to next state
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frame_re_out <= '0';
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if incCnt = '1' then -- handle counter
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cnt <= cnt + 1;
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elsif rstCnt = '1' then
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cnt <= 0;
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end if;
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if latchFrameData = '1' then -- latch stream data
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frameData_r <= frame_data_in;
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frame_re_out <= '1';
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end if;
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if determineOperation = '1' then -- determine ARP Operation value
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ARP_operation_r <= frameData_r(8);
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end if;
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if shiftSourceIPIn = '1' then -- shift in IP
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source_IP_r <= source_IP_r (15 downto 0) &
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frameData_r( 7 downto 0 ) & frameData_r( 15 downto 8 );
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end if;
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if shiftSourceMACIn = '1' then -- shift in MAC
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source_MAC_r <= source_MAC_r (31 downto 0) &
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frameData_r( 7 downto 0 ) & frameData_r( 15 downto 8 );
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end if;
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if updateARPTable = '1' then -- update ARP table
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if ARP_entry_IP_r = source_IP_r then -- We already have this ARP, so update
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ARP_entry_MAC_r <= source_MAC_r;
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else -- Lose one old ARP entry and add new one.
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ARP_entry_IP_old_r <= ARP_entry_IP_r;
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ARP_entry_MAC_old_r <= ARP_entry_MAC_r;
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ARP_entry_IP_r <= source_IP_r;
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ARP_entry_MAC_r <= source_MAC_r;
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end if;
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end if;
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if frame_invalid = '1' then
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frame_invalid_r <= '1';
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elsif clear_invalid = '1' then
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frame_invalid_r <= '0';
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end if;
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if new_frame_in = '1' then
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frame_len_r <= to_integer( unsigned( frame_len_in ));
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end if;
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-- gen_ARP_rep_out is asserted by doGenARPRep and will stay high until cleared
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-- by sending_reply_in
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if doGenARPRep = '1' then
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gen_ARP_rep_out <= '1'; -- when a request is needed assert gen_ARP_rep_out
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gen_ARP_IP_out <= source_IP_r; -- and latch the outgoing address
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elsif sending_reply_in = '1' then
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gen_ARP_rep_out <= '0'; -- when the request is been generated, stop requesting
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end if;
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end if;
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end process;
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process (presState, ARP_operation_r, cnt, new_frame_in, frame_invalid_r,
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new_word_valid_in, frameData_r, frame_valid_in, frame_len_r)
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begin
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-- defaulting of signals
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rstCnt <= '0';
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incCnt <= '0';
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shiftSourceIPIn <= '0';
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determineOperation <= '0';
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updateARPTable <= '0';
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shiftSourceIPIn <= '0';
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shiftSourceMACIn <= '0';
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latchFrameData <= '0';
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doGenARPRep <= '0';
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frame_invalid <= '0';
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clear_invalid <= '0';
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done_out <= '0';
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case presState is
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when stIdle =>
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-- wait for an ARP frame to arrive (udp_ip makes sure that it really is
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-- an ARP frame)
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if new_frame_in = '1' then
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nextState <= stHandleARP;
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rstCnt <= '1';
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else
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-- if there is data still coming to ARP, just pretend to be reading it
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if new_word_valid_in = '1' then
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latchFrameData <= '1';
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end if;
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nextState <= stIdle;
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end if;
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when stHandleARP =>
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-- receive a byte from the stream
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if new_word_valid_in = '0' then
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nextState <= stHandleARP;
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else
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nextState <= stOperate;
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latchFrameData <= '1';
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end if;
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when stOperate =>
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-- increment counter
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incCnt <= '1';
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-- choose state based on values in the header
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-- The following will make us ignore the frame (all values hexadecimal):
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-- Hardware Type /= 1
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-- Protocol Type /= 800
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-- Hardware Length /= 6
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-- Protocol Length /= 4
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-- Operation /= 1 or 2
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-- Target IP /= our IP (i.e. message is not meant for us)
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if (cnt = 0 and frameData_r /= x"0100") or
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(cnt = 1 and frameData_r /= x"0008") or -- MSByte = 0 to 7, LSByte = 8 to 15
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(cnt = 2 and frameData_r /= x"0406") or
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(cnt = 3 and frameData_r /= x"0100" and frameData_r /= x"0200") or
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(cnt = 12 and frameData_r /= own_ip_c( 23 downto 16 ) & own_ip_c( 31 downto 24 )) or
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(cnt = 13 and frameData_r /= own_ip_c( 7 downto 0 ) & own_ip_c( 15 downto 8 )) then
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--if ((cnt = "00000" or cnt = "00011" or cnt = "00110") and frameData_r /= 0 )or
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-- (cnt = "00001" and frameData_r /= 1) or
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-- (cnt = "00010" and frameData_r /= 8) or
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-- (cnt = "00100" and frameData_r /= 6) or
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-- (cnt = "00101" and frameData_r /= 4) or
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-- (cnt = "00111" and frameData_r /= 1 and frameData_r /= 2 )or
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-- (cnt = "11000" and frameData_r /= DEVICE_IP (31 downto 24)) or
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-- (cnt = "11001" and frameData_r /= DEVICE_IP (23 downto 16)) or
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-- (cnt = "11010" and frameData_r /= DEVICE_IP (15 downto 8)) or
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-- (cnt = "11011" and frameData_r /= DEVICE_IP (7 downto 0)) then
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frame_invalid <= '1';
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end if;
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-- frame len is in bytes, so divide by two
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if cnt = frame_len_r/2-1 then
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nextState <= stCheckValid; -- exit when data is totally received
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else
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nextState <= stHandleARP; -- otherwise loop until complete
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end if;
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-- latch and shift in signals from stream when needed
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if cnt = 3 then
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determineOperation <= '1';
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end if;
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if cnt = 4 or cnt = 5 or cnt = 6 then
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shiftSourceMACIn <= '1';
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end if;
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if cnt = 7 or cnt = 8 then
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shiftSourceIPIn <= '1';
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end if;
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when stCheckValid =>
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clear_invalid <= '1';
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done_out <= '1';
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nextState <= stIdle;
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if frame_valid_in = '1' and frame_invalid_r = '0' then
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-- frame didn't fail CRC and it's not invalid in any other way either
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-- generate a reply if required and wait for more messages
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if ARP_operation_r = '1' then
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doGenARPRep <= '1';
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end if;
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updateARPTable <= '1'; -- update the ARP table with the new data
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end if;
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when others => null;
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end case;
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end process;
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-- handle requests for entries in the ARP table.
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process (req_IP_in, ARP_entry_IP_r, ARP_entry_MAC_r, ARP_entry_IP_old_r, ARP_entry_MAC_old_r)
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begin
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if req_IP_in = ARP_entry_IP_r then -- check most recent entry
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valid_entry_out <= '1';
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lookup_MAC_out <= ARP_entry_MAC_r;
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elsif req_IP_in = ARP_entry_IP_old_r then -- check 2nd entry
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valid_entry_out <= '1';
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lookup_MAC_out <= ARP_entry_MAC_old_r;
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else -- if neither entry matches, valid = 0
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valid_entry_out <= '0';
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lookup_MAC_out <= (others => '1');
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end if;
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end process;
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end ARP_arch;
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