------------------------------------------------------------------------------- -- Title : frame alignment ------------------------------------------------------------------------------- -- File : frame_alignment.vhd ------------------------------------------------------------------------------- -- Description: Retrieves alignment of octet in a frame. -- Aligns using /A/ and /F/ characters. If these characters are on wrong spot, -- returns an error. May realign if requested. -- IF lane alignment is in use (more lanes are there), do not realign using -- frame alignment. Realign using lane alignment. ci_realign of frame alignment -- should remain low at all times. ------------------------------------------------------------------------------- library ieee; use ieee.std_logic_1164.all; use work.data_link_pkg.all; use work.transport_pkg.all; entity frame_alignment is generic ( SCRAMBLING : std_logic; -- Whether data are scrambled F : integer range 0 to 256 := 8; -- Number of octets in a frame K : integer range 0 to 32 := 1; -- Number of frames in a multiframe sync_char : std_logic_vector(7 downto 0) := "10111100"; -- K -- character -- for syncing A_char : std_logic_vector(7 downto 0) := "01111100"; -- Last -- character -- in multiframe F_char : std_logic_vector(7 downto 0) := "11111100"; -- Last -- character -- in frame F_replace_data : std_logic_vector(7 downto 0) := "11111100"; -- The character to replace with upon receiving /F/ with scrambled data A_replace_data : std_logic_vector(7 downto 0) := "01111100"); -- The character to replace with upon receiving /A/ with scrambled data port ( ci_char_clk : in std_logic; -- Character clock ci_frame_clk : in std_logic; -- Frame clock ci_reset : in std_logic; -- Reset (asynchronous, active low) ci_request_sync : in std_logic; -- Whether sync is requested ci_realign : in std_logic; -- Whether to realign to last -- alignment character di_char : in character_vector; -- The received character co_aligned : out std_logic; -- Whether the alignment is right co_error : out std_logic; -- Whether there was an error with -- the alignment co_correct_sync_chars : out integer; -- Number of alignment characters on -- same position in a row do_aligned_chars : out std_logic_vector(8*F - 1 downto 0); co_frame_state : out frame_state); -- Errors for current or next frame -- a characters in a frame end entity frame_alignment; architecture a1 of frame_alignment is type alignment_state is (INIT, ALIGNED, MISALIGNED); signal reg_state : alignment_state := INIT; signal next_frame_state : frame_state; signal buffer_character : std_logic_vector(7 downto 0) := "00000000"; signal buffer_raw_adjust_position : integer := 0; signal buffer_adjust_position : integer := 0; signal buffer_align_to : integer := 0; signal buffer_read_position : integer := 0; signal buffer_write_position : integer := 0; signal buffer_filled : std_logic := '0'; signal reg_last_frame_data : std_logic_vector(7 downto 0) := "00000000"; signal next_is_last_octet : std_logic := '0'; signal next_is_last_frame : std_logic := '0'; signal is_f : std_logic := '0'; signal is_a : std_logic := '0'; signal is_wrong_char : std_logic := '0'; signal reg_correct_sync_chars : integer := 0; signal reg_known_sync_char_position : integer range 0 to 256; signal next_octet_index : integer range 0 to F := 0; signal next_adjusted_octet_index : integer range 0 to F := 0; begin -- architecture a1 data_buffer: entity work.ring_buffer generic map ( BUFFER_SIZE => F*2, READ_SIZE => F, CHARACTER_SIZE => 8) port map ( ci_clk => ci_char_clk, ci_reset => ci_reset, ci_adjust_position => buffer_adjust_position, ci_read => ci_frame_clk, di_character => buffer_character, co_read => do_aligned_chars, co_read_position => buffer_read_position, co_write_position => buffer_write_position, co_filled => buffer_filled); next_frame: process (ci_frame_clk) is begin -- process next_frame if ci_reset = '0' then co_frame_state <= ('0', '0', '0', '0', '0', '0', '0', '0'); elsif ci_frame_clk'event and ci_frame_clk = '1' then -- rising clock edge co_frame_state <= next_frame_state; end if; end process next_frame; set_next: process (ci_char_clk, ci_frame_clk, ci_reset) is begin -- process set_next if ci_reset = '1' and ci_frame_clk'event and ci_frame_clk = '1' then if reg_state /= INIT then next_frame_state <= ('1', '0', '0', '0', '0', '0', '0', '0'); end if; end if; if ci_reset = '0' then -- asynchronous reset (active reg_state <= INIT; reg_last_frame_data <= (others => '0'); next_frame_state <= ('0', '0', '0', '0', '0', '0', '0', '0'); buffer_align_to <= -1; elsif ci_char_clk'event and ci_char_clk = '1' then -- rising clock edge -- set last_frame_data if this is the last frame and not /F/ or /A/ if next_is_last_octet = '1' and not (is_f = '1' or is_a = '1') then reg_last_frame_data <= di_char.d8b; end if; if ci_request_sync = '1' then reg_state <= INIT; next_frame_state <= ('0', '0', '0', '0', '0', '0', '0', '0'); elsif reg_state = INIT then next_frame_state <= ('0', '0', '0', '0', '0', '0', '0', '0'); -- if a or f, align to it and move to aligned if is_a = '1' or is_f = '1' then -- align to current character. buffer_align_to <= next_octet_index; next_frame_state <= ('1', '0', '0', '0', '0', '0', '0', '0'); reg_state <= ALIGNED; end if; else if di_char.kout = '1' and not (is_a = '1' or is_f = '1') then next_frame_state.invalid_characters <= '1'; end if; if di_char.disparity_error = '1' then next_frame_state.disparity_error <= '1'; end if; if di_char.missing_error then next_frame_state.not_in_table_error <= '1'; end if; if di_char.user_data = '0' then next_frame_state.user_data <= '0'; end if; if reg_state = ALIGNED then if is_wrong_char = '1' then next_frame_state.wrong_alignment <= '1'; reg_state <= MISALIGNED; reg_correct_sync_chars <= 1; reg_known_sync_char_position <= next_octet_index; end if; elsif reg_state = MISALIGNED then next_frame_state.wrong_alignment <= '1'; if is_wrong_char = '1' then if reg_known_sync_char_position = next_octet_index then reg_correct_sync_chars <= reg_correct_sync_chars + 1; else reg_known_sync_char_position <= next_octet_index; reg_correct_sync_chars <= 1; end if; elsif is_wrong_char = '0' and (is_f = '1' or is_a = '1') then reg_correct_sync_chars <= 0; reg_state <= ALIGNED; elsif ci_realign = '1' then -- align to last known sync char position buffer_align_to <= reg_known_sync_char_position + buffer_read_position; reg_state <= ALIGNED; end if; end if; end if; end if; -- clk, reset end process set_next; co_correct_sync_chars <= reg_correct_sync_chars; buffer_raw_adjust_position <= (buffer_align_to + 1 - buffer_read_position) mod F; buffer_adjust_position <= buffer_raw_adjust_position when buffer_raw_adjust_position <= F/2 + 1 else buffer_raw_adjust_position - F; is_wrong_char <= (is_f and not next_is_last_octet) or (is_a and not next_is_last_octet); buffer_character <= di_char.d8b when is_f = '0' and is_a = '0' else reg_last_frame_data when SCRAMBLING = '0' else F_replace_data when is_f = '1' else A_replace_data; next_adjusted_octet_index <= (buffer_write_position - buffer_read_position - buffer_adjust_position) mod F; next_octet_index <= (buffer_write_position - buffer_read_position) mod F; next_is_last_octet <= '1' when next_adjusted_octet_index = F - 1 else '0'; is_f <= '1' when di_char.d8b = F_char and di_char.kout = '1' else '0'; is_a <= '1' when di_char.d8b = A_char and di_char.kout = '1' else '0'; co_error <= '1' when reg_state = MISALIGNED else '0'; co_aligned <= '1' when reg_state = ALIGNED else '0'; end architecture a1;