//////////////////////////////////////////////////////////////////////////                                                              ////////  8051 stack pointer                                          ////////                                                              ////////  This file is part of the 8051 cores project                 ////////  http://www.opencores.org/cores/8051/                        ////////                                                              ////////  Description                                                 ////////   8051 special function register: stack pointer.             ////////                                                              ////////  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 sp (clk, rst, ram_rd_sel, ram_wr_sel, wr_addr, wr, wr_bit, data_in, data_out);// clk          clock// rst          reset// ram_rd_sel   ram read select, used tu calculate next value// ram_wr_sel   ram write select, used tu calculate next value// wr           write// wr_bit       write bit addresable// data_in      data input (from alu destiantion 1)// wr_addr      write address (if is addres of sp and white high must be written to sp)// data_out     data outputinput clk, rst, wr, wr_bit;input [1:0] ram_rd_sel;input [2:0] ram_wr_sel;input [7:0] data_in, wr_addr;output data_out;reg [7:0] data_out;////case of writing to stack pointeralways @(posedge clk)begin  if (rst)    data_out <= #1 `RST_SP;  else if ((wr_addr==`SFR_SP) & (wr) & !(wr_bit))    data_out <= #1 data_in;end//// popalways @(posedge clk)begin  if (ram_rd_sel==`RRS_SP) data_out <= #1 data_out-1'b1;end//// pushalways @(posedge clk)begin  if (ram_wr_sel==`RWS_SP) data_out <= #1 data_out+1'b1;endendmodule