//======================================================================
//
// math_selector.v
// ---------------
// Selector of math cores. Currently there is only one core in math -
// the modexp core. That core uses 12 bits and we simply ignore the
// top two bits of the address. If we add more math cores we will
// use these bits to select cores here.
//
//
//
// Authors: Joachim Strombergson, Paul Selkirk, Pavel Shatov
// Copyright (c) 2014-2015, 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.
//
//======================================================================

module math_selector
  (
   input wire           sys_clk,
   input wire           sys_rst_n,
   input wire           sys_ena,

   input wire [13: 0]   sys_eim_addr,
   input wire           sys_eim_wr,
   input wire           sys_eim_rd,
   output wire [31 : 0] sys_read_data,
   input wire [31 : 0]  sys_write_data
   );


   //----------------------------------------------------------------
   // List of Available Cores
   //----------------------------------------------------------------
   // Comment following lines to exclude cores from implementation.
   `define  USE_CORE_MODEXPS6


   //----------------------------------------------------------------
   // Address Decoder
   //----------------------------------------------------------------
`ifdef USE_CORE_MODEXPS6
   // upper  4 bits specify core being addressed
   wire [ 3: 0]         addr_core_num   = sys_eim_addr[13:10];
   // lower 10 bits specify register offset in core
   wire [ 9: 0]         addr_core_reg   = sys_eim_addr[ 9: 0];
`endif


   //----------------------------------------------------------------
   // Core Address Table
   //----------------------------------------------------------------
   `ifdef USE_CORE_MODEXPS6
   localparam   CORE_ADDR_MODEXPS6	= 4'd0;
   `endif


   //----------------------------------------------------------------
   // ModExpS6
   //----------------------------------------------------------------
   `ifdef USE_CORE_MODEXPS6
   wire [31: 0]         read_data_modexps6;
   wire                 enable_modexps6 = sys_ena && (addr_core_num == CORE_ADDR_MODEXPS6);
   modexps6_wrapper modexps6_inst
     (
      .clk(sys_clk),
      .reset_n(sys_rst_n),

      .cs(enable_modexps6 & (sys_eim_rd | sys_eim_wr)),
      .we(sys_eim_wr),

      .address(addr_core_reg),
      .write_data(sys_write_data),
      .read_data(read_data_modexps6)
      );
   `endif
   
   
   //----------------------------------------------------------------
   // Output (Read Data) Multiplexor
   //----------------------------------------------------------------
   reg [31: 0]          sys_read_data_mux;
   assign               sys_read_data = sys_read_data_mux;

   always @*
     //
   `ifdef USE_CORE_MODEXPS6
     if (addr_core_num == CORE_ADDR_MODEXPS6)
       begin
	  sys_read_data_mux = read_data_modexps6;
       end
     else
   `endif
       //
       begin
          sys_read_data_mux = {32{1'b0}};
       end


endmodule

//======================================================================
// EOF math_selector.v
//======================================================================