// ***************************************************************************
// ***************************************************************************
// Copyright (C) 2020, 2022 Analog Devices, Inc. All rights reserved.
// SPDX short identifier: ADIJESD204
// ***************************************************************************
// ***************************************************************************

`timescale 1ns/100ps

module jesd204_rx_header (
  input clk,
  input reset,

  input sh_lock,
  input [1:0] header,

  input [1:0] cfg_header_mode,  // 0 - CRC12 ; 1 - CRC3; 2 - FEC; 3 - CMD
  input [4:0] cfg_rx_thresh_emb_err,
  input [7:0] cfg_beats_per_multiframe,

  output emb_lock,

  output valid_eomb,
  output valid_eoemb,
  // Received header data qualified by valid_eomb
  output [11:0] crc12,
  output [2:0] crc3,
  output [25:0] fec,
  output [18:0] cmd,
  output reg [7:0] sh_count = 'h0,

  output [2:0] status_lane_emb_state,
  output reg event_invalid_header,
  output reg event_unexpected_eomb,
  output reg event_unexpected_eoemb
);

  localparam STATE_EMB_INIT = 3'b001;
  localparam STATE_EMB_HUNT = 3'b010;
  localparam STATE_EMB_LOCK = 3'b100;

  localparam BIT_EMB_INIT = 0;
  localparam BIT_EMB_HUNT = 1;
  localparam BIT_EMB_LOCK = 2;

  reg [2:0] state = STATE_EMB_INIT;
  reg [2:0] next_state;

  reg [31:0] sync_word = 'h0;

  wire header_bit;
  wire invalid_sequence;
  wire invalid_eoemb;
  wire invalid_eomb;
  wire [6:0] cmd0;
  wire [6:0] cmd1;
  wire [18:0] cmd3;
  wire eoemb;
  wire eomb;

  assign header_bit = header == 2'b01;

  always @(posedge clk) begin
    sync_word <= {sync_word[30:0],header_bit};
  end

  assign crc12 = {sync_word[31:29],sync_word[27:25],
                  sync_word[23:21],sync_word[19:17]};
  assign crc3 = {sync_word[31:29]};
  assign cmd0 = {sync_word[15:13],sync_word[11],
                 sync_word[7:5]};
  assign cmd1 = {sync_word[27:25],
                 sync_word[19:17],
                 sync_word[11]};
  assign cmd3 = {sync_word[31:29],sync_word[27:25],
                 sync_word[23:21],sync_word[19:17],
                 sync_word[15:13],sync_word[11],
                 sync_word[7:5]};

  assign cmd = cfg_header_mode == 0 ? {12'b0,cmd0} :
               cfg_header_mode == 1 ? {12'b0,cmd1} :
               cfg_header_mode == 3 ? cmd3 : 'b0;

  assign fec = {sync_word[31:10],sync_word[8:5]};

  assign eomb  = sync_word[4:0] == 5'b00001;
  assign eoemb = sync_word[9] & eomb;

  always @(posedge clk) begin
    if (next_state[BIT_EMB_INIT] || sh_count == cfg_beats_per_multiframe) begin
      sh_count <= 'h0;
    end else begin
      sh_count <= sh_count + 8'b1;
    end
  end

  reg [1:0] emb_vcount = 'b0;
  always @(posedge clk) begin
    if (state[BIT_EMB_INIT]) begin
      emb_vcount <= 'b0;
    end else if (state[BIT_EMB_HUNT] && (sh_count == 0 && eoemb)) begin
      emb_vcount <= emb_vcount + 'b1;
    end
  end

  reg [4:0] emb_icount = 'b0;
  always @(posedge clk) begin
    if (state[BIT_EMB_INIT]) begin
      emb_icount <= 'b0;
    end else if (state[BIT_EMB_LOCK]) begin
      if (sh_count == 0 && eoemb) begin
        emb_icount <= 'b0;
      end else if (invalid_eoemb || invalid_eomb) begin
        emb_icount <= emb_icount + 5'b1;
      end
    end
  end

  always @(*) begin
    next_state = state;
    case (state)
      STATE_EMB_INIT:
        if (eoemb) begin
          next_state = STATE_EMB_HUNT;
        end
      STATE_EMB_HUNT:
        if (invalid_sequence) begin
          next_state = STATE_EMB_INIT;
        end else if (eoemb && emb_vcount == 2'd3) begin
          next_state = STATE_EMB_LOCK;
        end
      STATE_EMB_LOCK:
        if (emb_icount == cfg_rx_thresh_emb_err) begin
          next_state = STATE_EMB_INIT;
        end
    endcase
    if (sh_lock == 1'b0) next_state = STATE_EMB_INIT;
  end

  assign invalid_eoemb = (sh_count == 0 && ~eoemb);
  assign invalid_eomb = (sh_count[4:0] == 0 && ~eomb);
  assign valid_eomb = next_state[BIT_EMB_LOCK] && eomb;
  assign valid_eoemb = next_state[BIT_EMB_LOCK] && eoemb;

  assign invalid_sequence = (invalid_eoemb || invalid_eomb);

  always @(posedge clk) begin
    if (reset == 1'b1) begin
      state <= STATE_EMB_INIT;
    end else begin
      state <= next_state;
    end
  end

  assign emb_lock = next_state[BIT_EMB_LOCK];

  // Status & error events
  assign status_lane_emb_state = state;

  always @(posedge clk) begin
    event_invalid_header <= (~state[BIT_EMB_INIT]) && (header[0] == header[1]);
    event_unexpected_eomb <= (~state[BIT_EMB_INIT]) && (sh_count[4:0] != 0 && eomb);
    event_unexpected_eoemb <= (~state[BIT_EMB_INIT]) && invalid_eoemb;
  end

endmodule