rom.v

another 8051 core porocesssor vhdl source code

//*******************************************************************       //
//IMPORTANT NOTICE                                                          //
//================                                                          //
//Copyright Mentor Graphics Corporation 1996 - 1999.  All rights reserved.  //
//This file and associated deliverables are the trade secrets,              //
//confidential information and copyrighted works of Mentor Graphics         //
//Corporation and its licensors and are subject to your license agreement   //
//with Mentor Graphics Corporation.                                         //
//                                                                          //
//Use of these deliverables for the purpose of making silicon from an IC    //
//design is limited to the terms and conditions of your license agreement   //
//with Mentor Graphics If you have further questions please contact Mentor  //
//Graphics Customer Support.                                                //
//                                                                          //
//This Mentor Graphics core (m8051 v1999.120) was extracted on              //
//workstation hostid _hostid_ Inventra                                      //
///////////////////////////////////////////////////////////////////////////////
// File                 :       rom.v
// Author               :       Ken Dennis
// Library              :       WORK
// Created on           :       July 2nd 1996
// Purpose              :       ROM Model
// Version              :       1.001
// Mod_Date             :       July 3rd, 1996
// Mod_Hist             :   
///////////////////////////////////////////////////////////////////////////////
// Hierarchy record :
// called by:
// 
// calls to:
// none
///////////////////////////////////////////////////////////////////////////////
//Function of the entity : A model of the ROM has been constructed.
//Data will be loaded from a hex file (default_rom.rom) into the ROM.
///////////////////////////////////////////////////////////////////////////////

module rom (out_data, address, ncs, nromrd);
//*******************************************************************       //
//IMPORTANT NOTICE                                                          //
//================                                                          //
//Copyright Mentor Graphics Corporation 1996 - 1999.  All rights reserved.  //
//This file and associated deliverables are the trade secrets,              //
//confidential information and copyrighted works of Mentor Graphics         //
//Corporation and its licensors and are subject to your license agreement   //
//with Mentor Graphics Corporation.                                         //
//                                                                          //
//Use of these deliverables for the purpose of making silicon from an IC    //
//design is limited to the terms and conditions of your license agreement   //
//with Mentor Graphics If you have further questions please contact Mentor  //
//Graphics Customer Support.                                                //
//                                                                          //
//This Mentor Graphics core (m8051 v1999.120) was extracted on              //
//workstation hostid _hostid_ Inventra                                      //

parameter ROM_SIZE = 4096;
parameter ROM_WIDTH = 12;
`define OP_DEL 12.5      // Set read delay in ns
//
// The ROM model opens a specified Intel style Hex files and loads its self
// after load is finished it acts just like a ROM.
// 

input [ROM_WIDTH -1:0] address;
input ncs;
input nromrd;
output [7:0] out_data;

reg [7:0] rom_data [0:ROM_SIZE -1];  // 4K Word
wire [7:0] out_data;
integer i;

initial
begin
   for (i=0;i<ROM_SIZE;i= i+1)
      rom_data[i] <= 8'b00000000;
   #1;
   $readmemh("default_rom.rom",rom_data);
end

assign out_data = ({ncs,nromrd} === 2'b00) ? rom_data[address]:8'bzzzzzzzz;

endmodule