//////////////////////////////////////////////////////////////////////////                                                              ////////  8051 external address select                                ////////                                                              ////////  This file is part of the 8051 cores project                 ////////  http://www.opencores.org/cores/8051/                        ////////                                                              ////////  Description                                                 ////////   Multiplexer wiht whitch we define external address         ////////   (dptr or Ri)                                               ////////                                                              ////////  To Do:                                                      ////////   nothing                                                    ////////                                                              ////////  Author(s):                                                  ////////      - Simon Teran, simont@opencores.org                     ////////                                                              //////////////////////////////////////////////////////////////////////////////                                                              //////// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////////                                                              //////// This source file may be used and distributed without         //////// restriction provided that this copyright statement is not    //////// removed from the file and that any derivative work contains  //////// the original copyright notice and the associated disclaimer. ////////                                                              //////// This source file is free software; you can redistribute it   //////// and/or modify it under the terms of the GNU Lesser General   //////// Public License as published by the Free Software Foundation; //////// either version 2.1 of the License, or (at your option) any   //////// later version.                                               ////////                                                              //////// This source 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.  See the GNU Lesser General Public License for more //////// details.                                                     ////////                                                              //////// You should have received a copy of the GNU Lesser General    //////// Public License along with this source; if not, download it   //////// from http://www.opencores.org/lgpl.shtml                     ////////                                                              ////////////////////////////////////////////////////////////////////////////// ver: 1//module ext_addr_sel (clk, select, write, dptr_hi, dptr_lo, ri, addr_out);input select, write, clk;input [7:0] dptr_hi, dptr_lo, ri;output [15:0] addr_out;reg state;reg [15:0] buff;wire [15:0] tmp;assign tmp = select ? {8'h00, ri} : {dptr_hi, dptr_lo};assign addr_out = state ? buff : tmp;always @(posedge clk)  if (select)    buff <= #1 {8'h00, ri};  else buff <= #1 {dptr_hi, dptr_lo};always @(posedge clk)  if (write)    state <= #1 1'b1;  else state <= #1 1'b0;endmodule