// ***************************************************************************
// ***************************************************************************
// Copyright 2014 - 2017 (c) Analog Devices, Inc. All rights reserved.
//
// This core  is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE.
//
// Redistribution and use of source or resulting binaries, with or without modification
// of this file, are permitted under one of the following two license terms:
//
//   1. The GNU General Public License version 2 as published by the
//      Free Software Foundation, which can be found in the top level directory of
//      the repository (LICENSE_GPL2), and at: <https://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
//
// OR
//
//   2. An ADI specific BSD license as noted in the top level directory, or on-line at:
//      https://github.com/analogdevicesinc/hdl/blob/master/LICENSE_ADIBSD
//      This will allow to generate bit files and not release the source code,
//      as long as it attaches to an ADI device.
//
// ***************************************************************************
// ***************************************************************************

module cic_comb #(
  parameter DATA_WIDTH = 32,
  parameter SEQ = 1,
  parameter STAGE_WIDTH = 1,
  parameter NUM_STAGES = 1
) (
  input clk,
  input ce,
  input [NUM_STAGES-1:0] enable,
  input [DATA_WIDTH-1:0] data_in,
  output [DATA_WIDTH-1:0] data_out
);

reg [SEQ-1:0] storage[0:DATA_WIDTH-1];
reg [DATA_WIDTH-1:0] state = 'h00;

reg [2:0] counter = 'h00;
reg active = 1'b0;

integer x;

initial begin
  for (x = 0; x < DATA_WIDTH; x = x + 1) begin
    storage[x] = 'h00;
  end
end

generate if (SEQ != 1) begin

always @(posedge clk) begin
  if (ce == 1'b1) begin
    counter <= SEQ-1;
    active <= 1'b1;
  end else if (active == 1'b1) begin
    counter <= counter - 1'b1;
    if (counter == 'h1) begin
      active <= 1'b0;
    end
  end
end

end
endgenerate

wire [DATA_WIDTH-1:0] mask;
reg [DATA_WIDTH-1:0] data_in_seq;
wire [DATA_WIDTH-1:0] storage_out;
wire [DATA_WIDTH-1:0] diff = (data_in_seq | ~mask) - (storage_out & mask);

always @(*) begin
  if (ce == 1'b1) begin
    data_in_seq <= data_in;
  end else begin
    data_in_seq <= SEQ != 1 ? state : 'h00;
  end
end

generate
genvar i, j;

for (j = 0; j < NUM_STAGES; j = j + 1) begin
  localparam k = NUM_STAGES - j - 1;
  localparam H = DATA_WIDTH - STAGE_WIDTH * j - 1;
  localparam L = k == 0 ? 0 : DATA_WIDTH - STAGE_WIDTH * (j+1);

  assign mask[H:L] = {{H-L{1'b1}},k != 0 ? enable[k] : 1'b1};

  for (i = L; i <= H; i = i + 1) begin: shift_r
    always @(posedge clk) begin
      if (enable[k] == 1'b1 && (ce == 1'b1 || active == 1'b1)) begin
        if (SEQ > 1) begin
          storage[i] <= {storage[i][SEQ-2:0],data_in_seq[i]};
        end else begin
          storage[i] <= data_in_seq[i];
        end
      end
    end

    assign storage_out[i] = storage[i][SEQ-1];

  end

  always @(posedge clk) begin
    if (enable[k] == 1'b1 && (ce == 1'b1 || active == 1'b1)) begin
      state[H:L] <= diff[H:L];
    end
  end
end

endgenerate

assign data_out = state;

endmodule