-------------------------------------------------------------------------------
-- Title : controller of data link layer
-------------------------------------------------------------------------------
-- File : link_controller.vhd
-------------------------------------------------------------------------------
-- Description: Controller for link layer, handling CGS and ILAS.
--
-------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use work.data_link_pkg.all;
-- What does it do?
-- Well, it manages the states (init, cgs, ilas, data)
-- It sends sync if needed (irecoverrable error detected). It holds? ILAS data.
-- It should get all the control outputs from lane_alignment,
-- frame_alignment, an8b10bdecoder, char_alignment.
-- It should get the current data from an8b10bdecoder
entity link_controller is
generic (
CHANNEL_WIDTH : integer := 1; -- Number of characters going in at once
F : integer range 1 to 256; -- Number of octets in a frame
K : integer range 1 to 32; -- Number of frames in a multiframe
K_character : std_logic_vector(7 downto 0) := "10111100"); -- Sync character
port (
ci_frame_clk : in std_logic; -- Frame clock
ci_link_clk : in std_logic; -- Link clock
ci_reset : in std_logic; -- Reset (asynchronous, active low)
di_chars : in character_array(0 to CHANNEL_WIDTH-1); -- Output character from 8b10b decoder
do_config : out link_config; -- Config found in ILAS
ci_lane_alignment_error : in std_logic; -- Signals a problem with lane
-- alignment in this data link
-- (see lane alighnment component)
ci_lane_alignment_aligned : in std_logic; -- Signals that lane is
-- correctly aligned (see
-- lane_alignment component)
ci_lane_alignment_ready : in std_logic; -- Signals that the lane received
-- /A/ and is waiting to start
-- sending data (see
-- lane_alignment component)
ci_frame_alignment_error : in std_logic; -- Signals that the frame was misaligned.
ci_frame_alignment_aligned : in std_logic; -- Signals that the frame end
-- was found and did not change.
ci_resync : in std_logic; -- Whether to start syncing again.
co_synced : out std_logic; -- Whether the lane is synced (received
-- 4 /K/ characters and proceeds correctly)
co_state : out link_state; -- The state of the lane.
co_uncorrectable_error : out std_logic; -- Detected an uncorrectable
-- error, has to resync (ilas
-- parsing error)
co_error : out std_logic); -- Detected any error, processing may
-- differ
end entity link_controller;
architecture a1 of link_controller is
constant SYNC_COUNT : integer range 0 to 4 := 4;
constant FULL_SYNCHRONIZATION_AFTER : integer range 0 to 4 := 4;
signal synced : std_logic := '0';
signal full_synchronization : std_logic := '0'; -- Assumed after 4 /K/
-- characters + 4 more 8b10b
-- correct characters
signal correct_8b10b_characters : integer range 0 to FULL_SYNCHRONIZATION_AFTER;
signal reg_state : link_state := INIT;
signal reg_k_counter : integer range 0 to 15 := 0;
signal ilas_finished : std_logic := '0';
signal ilas_error : std_logic := '0';
signal ilas_wrong_chksum : std_logic := '0';
signal ilas_unexpected_char : std_logic := '0';
signal any_missing_error : std_logic;
signal any_disparity_error : std_logic;
begin -- architecture a1
ilas : entity work.ilas_parser
generic map (
CHANNEL_WIDTH => CHANNEL_WIDTH,
F => F,
K => K)
port map (
ci_char_clk => ci_char_clk,
ci_reset => ci_reset,
ci_state => reg_state,
di_chars => di_chars,
do_config => do_config,
co_finished => ilas_finished,
co_error => ilas_error,
co_wrong_chksum => ilas_wrong_chksum,
co_unexpected_char => ilas_unexpected_char);
set_state: process (ci_link_clk, ci_reset) is
variable chars_error : std_logic := '0';
variable chars_missing_error : std_logic := '0';
variable chars_disparity_error : std_logic := '0';
variable k_count : integer := 0;
begin -- process set_state
if ci_reset = '0' then -- asynchronous reset (active low)
reg_state <= INIT;
reg_k_counter <= '0';
correct_8b10b_characters <= 0;
elsif ci_link_clk'event and ci_link_clk = '1' then -- rising clock edge
k_count := reg_k_counter;
for i in 0 to CHANNEL_WIDTH - 1 loop
if di_chars(i).disparity_error = '1' then
chars_disparity_error := '1';
end if;
if di_chars(i).missing_error = '1' then
chars_missing_error := '1';
end if;
if di_chars(i).d8b = K_character and di_chars(i).kout = '1' then
k_count := k_count + 1;
else
k_count := 0;
end if;
end loop; -- i
chars_error := chars_missing_error or chars_disparity_error;
if correct_8b10b_characters < FULL_SYNCHRONIZATION_AFTER and char_error = '0' then
if correct_8b10b_characters + CHANNEL_WIDTH > FULL_SYNCHRONIZATION_AFTER then
correct_8b10b_characters <= FULL_SYNCHRONIZATION_AFTER;
else
correct_8b10b_characters <= correct_8b10b_characters + CHANNEL_WIDTH;
end if;
end if;
if ci_resync = '1' or (full_synchronization = '0' and char_error = '1') then
reg_state <= INIT;
reg_k_counter <= 0;
elsif reg_state = CGS then
if reg_k_counter < SYNC_COUNT then
correct_8b10b_characters <= 1;
reg_k_counter <= k_count;
elsif k_count = 0 then
reg_state <= ILS;
end if;
elsif k_count > 0 then
reg_state <= CGS;
reg_k_counter <= 0;
elsif reg_state = ILS then
if ilas_finished = '1' then
reg_state <= DATA;
elsif ilas_error = '1' then
reg_state <= INIT;
end if;
elsif reg_state = DATA then
-- uncorrectable error? resync.
end if;
end if;
end process set_state;
synced <= '0' when reg_state = INIT or (reg_state = CGS and reg_k_counter < SYNC_COUNT) else '1';
full_synchronization <= '0' when synced = '0' or correct_8b10b_characters < FULL_SYNCHRONIZATION_AFTER else '1';
co_synced <= synced;
co_state <= reg_state;
-- TODO: add ILAS errors, add CGS error in case sync does not happen for long
-- time
co_error <= ci_lane_alignment_error or ci_frame_alignment_error or any_missing_error or any_disparity_error;
co_uncorrectable_error <= ilas_error;
end architecture a1;