//======================================================================
//
// alpha_top.v
// ------------
// Top module for the Cryptech Alpha FPGA framework. This design
// allow us to run the FMC interface at one clock and cores including
// core selector with the always present global clock.
//
//
// Author: Pavel Shatov
// Copyright (c) 2016, NORDUnet A/S All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// - Redistributions of source code must retain the above copyright
//   notice, this list of conditions and the following disclaimer.
//
// - Redistributions in binary form must reproduce the above copyright
//   notice, this list of conditions and the following disclaimer in the
//   documentation and/or other materials provided with the distribution.
//
// - Neither the name of the NORDUnet nor the names of its contributors may
//   be used to endorse or promote products derived from this software
//   without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
//======================================================================

`timescale 1ns / 1ps

module alpha_fmc_top
  (
   input wire 	      gclk_pin, // 50 MHz

   input wire 	      ct_noise, // cryptech avalanche noise circuit

   input wire 	      fmc_clk, // clock
   input wire [23: 0] fmc_a, // address
   inout wire [31: 0] fmc_d, // data
   input wire 	      fmc_ne1, // chip select
   input wire 	      fmc_noe, // output enable
   input wire 	      fmc_nwe, // write enable
   input wire 	      fmc_nl, // latch enable
   output wire 	      fmc_nwait,// wait

   output wire 	      mkm_sclk,
   output wire 	      mkm_cs_n,
   input wire 	      mkm_do,
   output wire 	      mkm_di,

   output wire [7: 0] gpio_a,
   output wire [7: 0] gpio_b,
   output wire [3: 0] led_pins  // {red, yellow, green, blue}
   );


   //----------------------------------------------------------------
   // Dummy assignments to bypass unconnected outpins pins check in BitGen
   //----------------------------------------------------------------
   assign led_pins[3:1] = 3'b000;


   //----------------------------------------------------------------
   // Clock Manager
   //
   // Clock manager is used to generate SYS_CLK from GCLK
   // and implement the reset logic.
   // ----------------------------------------------------------------
   wire               sys_clk;
   wire               sys_rst_n;

   alpha_clkmgr #
     (
      .CLK_OUT_MUL      (20.0),    // 2..64
      .CLK_OUT_DIV      (20.0)     // 1..128
      )
   clkmgr
     (
      .gclk      (gclk_pin),

      .sys_clk   (sys_clk),
      .sys_rst_n (sys_rst_n)
      );


   //----------------------------------------------------------------
   // BUFG
   //
   // FMC clock must be routed through the global clocking backbone.
   // ----------------------------------------------------------------
   wire               fmc_clk_bug;

   BUFG BUFG_fmc_clk
     (
      .I                (fmc_clk),
      .O                (fmc_clk_bufg)
      );



   //----------------------------------------------------------------
   // FMC Arbiter
   //
   // FMC arbiter handles FMC access and transfers it into
   // `sys_clk' clock domain.
   //----------------------------------------------------------------

   wire [23: 0]       sys_fmc_addr;     // address
   wire               sys_fmc_wren;     // write enable
   wire               sys_fmc_rden;     // read enable
   wire [31: 0]       sys_fmc_dout;     // data output (from STM32 to FPGA)
   wire [31: 0]       sys_fmc_din;      // data input (from FPGA to STM32)

   fmc_arbiter #
     (
      .NUM_ADDR_BITS(24)        // change to 26 when Alpha is alive!
      )
   fmc
     (
      .fmc_clk(fmc_clk_bufg),
      .fmc_a(fmc_a),
      .fmc_d(fmc_d),
      .fmc_ne1(fmc_ne1),
      .fmc_nl(fmc_nl),
      .fmc_nwe(fmc_nwe),
      .fmc_noe(fmc_noe),
      .fmc_nwait(fmc_nwait),

      .sys_clk(sys_clk),

      .sys_addr(sys_fmc_addr),
      .sys_wr_en(sys_fmc_wren),
      .sys_rd_en(sys_fmc_rden),
      .sys_data_out(sys_fmc_dout),
      .sys_data_in(sys_fmc_din)
      );


   //----------------------------------------------------------------
   // LED Driver
   //
   // A simple utility LED driver that turns on the Alpha
   // board LED when the FMC interface is active.
   //----------------------------------------------------------------
   fmc_indicator led
     (
      .sys_clk(sys_clk),
      .sys_rst_n(sys_rst_n),
      .fmc_active(sys_fmc_wren | sys_fmc_rden),
      .led_out(led_pins[0])
      );


   //----------------------------------------------------------------
   // Core Selector
   //
   // This multiplexer is used to map different types of cores, such as
   // hashes, RNGs and ciphers to different regions (segments) of memory.
   //----------------------------------------------------------------

   core_selector cores
     (
      .sys_clk(sys_clk),
      .sys_rst_n(sys_rst_n),

      .sys_fmc_addr(sys_fmc_addr),
      .sys_fmc_wr(sys_fmc_wren),
      .sys_fmc_rd(sys_fmc_rden),
      .sys_write_data(sys_fmc_dout),
      .sys_read_data(sys_fmc_din),

      .noise(ct_noise),

      .mkm_sclk(mkm_sclk),
      .mkm_cs_n(mkm_cs_n),
      .mkm_do(mkm_do),
      .mkm_di(mkm_di)
      );


  //----------------------------------------------------------------
  // sys_clk_toggle
  //
  // Simple circuit that allows observation of the sys_clk on
  // an output pin. The sys_clk is divided down to allow
  // measurement with simple equipment.
  //
  // One toggle cycle will be 2 * TOGGLE_DELAY_CYCLES. The
  // number of cycles are selected to generate a 500 kHz period
  // when sys_clk is running at 50 MHz.
  //
  // The toggle signal is presented at pin 0 of both GPIO banks
  // available to the FPGA on the Alpha board.
  //----------------------------------------------------------------
  localparam TOGGLE_DELAY_CYCLES = 50;

  reg [15 : 0] toggle_ctr_reg;
  reg [15 : 0] toggle_ctr_new;

  reg toggle_reg;
  reg toggle_new;
  reg toggle_we;

  assign gpio_a = {7'b0101010, toggle_reg};
  assign gpio_b = {7'b1010101, toggle_reg};

  always @(posedge sys_clk)
    begin: sys_clk_toggle_reg_update
      if (!sys_rst_n)
        begin
          toggle_ctr_reg <= 32'h0;
          toggle_reg     <= 1'b0;
        end
      else
        begin
          toggle_ctr_reg <= toggle_ctr_new;

          if (toggle_we)
            toggle_reg <= toggle_new;
        end
    end

  always @*
    begin : sys_clk_toggle
      toggle_new = ~toggle_reg;
      toggle_we  = 1'b0;

      if (toggle_ctr_reg == TOGGLE_DELAY_CYCLES)
        begin
          toggle_ctr_new = 32'h0;
          toggle_we      = 1'b1;
        end
      else
        toggle_ctr_new = toggle_ctr_reg + 1'b1;
    end

endmodule // alpha_fmc_top