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//////////////////////////////////////////////////////////////////////

////                                                              ////

////  8051 exteranl program rom                                   ////

////                                                              ////

////  This file is part of the 8051 cores project                 ////

////  http://www.opencores.org/cores/8051/                        ////

////                                                              ////

////  Description                                                 ////

////   external program rom for 8051 core                         ////

////                                                              ////

////  To Do:                                                      ////

////   Nothing                                                    ////

////                                                              ////

////  Author(s):                                                  ////

////      - Simon Teran, simont@opencores.org                     ////

////                                                              ////

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////                                                              ////

//// 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                     ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

//

// CVS Revision History

//

// $Log: not supported by cvs2svn $

// Revision 1.1  2003/04/02 11:38:40  simont

// initial inport

//

// Revision 1.1  2002/10/17 18:56:13  simont

// initial CVS input

//

//

module oc8051_xrom (rst, clk, addr, data, stb_i, cyc_i, ack_o);

parameter DELAY=5;

input rst, clk, stb_i, cyc_i;

input [15:0] addr;

output ack_o;

output [31:0] data;

reg ack_o;

reg [31:0] data;

reg [7:0] buff [0:65535];

//reg [7:0] buff [8388607:0];

reg [2:0] cnt;

integer i;

wire [7:0] buff_0 = buff [0];

wire [7:0] buff_1 = buff [1];

wire [7:0] buff_2 = buff [2];

wire [7:0] buff_3 = buff [3];

initial

begin

//  for (i=0; i<65536; i=i+1)

//    buff [i] = 8'h00;

  $readmemh("./dat/oc8051_xrom.in", buff);

  for (i=0; i<10; i=i+1)

    $display("i : %h",buff [i] );

end

always @(posedge clk or posedge rst)

begin

  if (rst) begin

    data <= #1 31'h0;

    ack_o <= #1 1'b0;

  end else if (stb_i && ((DELAY==3'b000) || (cnt==3'b000))) begin

    data <= #1 {buff[addr+3], buff[addr+2], buff[addr+1], buff [addr]};

    ack_o <= #1 1'b1;

  end else

    ack_o <= #1 1'b0;

end

always @(posedge clk or posedge rst)

begin

  if (rst)

    cnt <= #1 DELAY;

  else if (cnt == 3'b000)

    cnt <= #1 DELAY;

  else if (stb_i)

    cnt <= #1 cnt - 3'b001;

  else cnt <= #1 DELAY;

end

endmodule