------------------------------------------------------------------------------- -- 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; entity frame_alignment is generic ( 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_reset : in std_logic; -- Reset (asynchronous, active low) ci_F : in integer range 0 to 256; -- The number of octets in a frame ci_K : in integer range 0 to 32; -- The number of frames in a multiframe ci_request_sync : in std_logic; -- Whether sync is requested ci_scrambled : in std_logic; -- Whether the data is scrambled 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_char : out frame_character); -- The output character -- (going to transport layer) end entity frame_alignment; architecture a1 of frame_alignment is type alignment_state is (INIT, RECEIVED_K, ALIGNED, MISALIGNED); signal reg_state : alignment_state := INIT; 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_octet_index : integer range 0 to 256 := 0; signal reg_frame_index : integer range 0 to 32 := 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 256 := 0; signal next_frame_index : integer range 0 to 32 := 0; signal next_char : character_vector := ('0', '0', '0', "00000000", '0'); begin -- architecture a1 set_next: process (ci_char_clk, ci_reset) is begin -- process set_next if ci_reset = '0' then -- asynchronous reset (active low) reg_frame_index <= 0; reg_octet_index <= 0; do_char <= ('0', '0', '0', "00000000", 0, 0, '0'); reg_state <= INIT; reg_correct_sync_chars <= 0; elsif ci_char_clk'event and ci_char_clk = '1' then -- rising clock edge do_char.kout <= next_char.kout; do_char.d8b <= next_char.d8b; do_char.disparity_error <= next_char.disparity_error; do_char.missing_error <= next_char.missing_error; do_char.user_data <= next_char.user_data; do_char.frame_index <= reg_frame_index; -- 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; reg_frame_index <= 0; reg_octet_index <= 0; do_char.octet_index <= 0; do_char.frame_index <= 0; elsif di_char.kout = '1' and di_char.d8b = sync_char then reg_state <= RECEIVED_K; reg_frame_index <= 0; reg_octet_index <= 0; do_char.octet_index <= 0; do_char.frame_index <= 0; elsif reg_state = INIT then reg_frame_index <= 0; reg_octet_index <= 0; do_char.octet_index <= 0; do_char.frame_index <= 0; elsif reg_state = RECEIVED_K then reg_frame_index <= 0; reg_octet_index <= 0; do_char.octet_index <= 0; do_char.frame_index <= 0; if di_char.d8b /= sync_char or di_char.kout = '0' then reg_state <= ALIGNED; end if; -- switch to aligned else reg_frame_index <= next_frame_index; reg_octet_index <= next_octet_index; do_char.octet_index <= next_octet_index; do_char.frame_index <= next_frame_index; if reg_state = ALIGNED then if is_wrong_char = '1' then reg_state <= MISALIGNED; reg_correct_sync_chars <= 1; reg_known_sync_char_position <= reg_octet_index; end if; elsif reg_state = MISALIGNED then if is_wrong_char = '1' then if reg_known_sync_char_position = reg_octet_index then reg_correct_sync_chars <= reg_correct_sync_chars + 1; else reg_known_sync_char_position <= reg_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 reg_correct_sync_chars <= 0; reg_octet_index <= (reg_octet_index + ((ci_F - 1) - reg_known_sync_char_position)) mod ci_F; do_char.octet_index <= (reg_octet_index + ((ci_F - 1) - reg_known_sync_char_position)) mod ci_F; reg_frame_index <= reg_frame_index + 1; do_char.frame_index <= reg_frame_index + 1; reg_state <= ALIGNED; end if; end if; end if; -- in RECEIVED_K end if; -- clk, reset end process set_next; is_wrong_char <= (is_f and not next_is_last_octet) or (is_a and not (next_is_last_octet and next_is_last_frame)); next_char.kout <= di_char.kout when is_f = '0' and is_a = '0' else '0'; next_char.d8b <= di_char.d8b when is_f = '0' and is_a = '0' else reg_last_frame_data when ci_scrambled = '0' else F_replace_data when is_f = '1' else A_replace_data; next_char.disparity_error <= di_char.disparity_error; next_char.missing_error <= di_char.missing_error; next_char.user_data <= di_char.user_data; next_is_last_octet <= '1' when next_octet_index = ci_F - 1 else '0'; next_is_last_frame <= '1' when next_frame_index = ci_K - 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'; next_frame_index <= reg_frame_index when reg_octet_index < (ci_F - 1) else (reg_frame_index + 1) mod ci_K; next_octet_index <= (reg_octet_index + 1) mod ci_F; co_correct_sync_chars <= reg_correct_sync_chars; co_error <= '1' when reg_state = MISALIGNED else '0'; co_aligned <= '1' when reg_state = ALIGNED else '0'; end architecture a1;