Subversion Repositories oms8051mini

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

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////  8051 wishbone interface to instruction rom                  ////

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

////  http://www.opencores.org/cores/oms8051mini/                 ////

////                                                              ////

////  Description                                                 ////

////                                                              ////

////                                                              ////

////  To Do:                                                      ////

////    nothing                                                   ////

////                                                              ////

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

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

////      - Dinesh Annayya, dinesha@opencores.org                 ////

////                                                              ////

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////   v0.0 - Dinesh A, 5th Jan 2017

////        1. Active edge of reset changed from High to Low

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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 1.5  2003/05/05 10:34:27  simont

// registering outputs.

//

// Revision 1.4  2003/04/16 10:02:45  simont

// fix bug (cyc_o and stb_o)

//

// Revision 1.3  2003/04/03 19:19:02  simont

// change adr_i and adr_o length.

//

// Revision 1.2  2003/01/13 14:14:41  simont

// replace some modules

//

// Revision 1.1  2002/10/28 16:42:08  simont

// initial import

//

//

//

module oc8051_wb_iinterface(resetn, clk,

                  adr_i, dat_o, cyc_i, stb_i, ack_o,

                  adr_o, dat_i, cyc_o, stb_o, ack_i

                  );

//

// resetn           (in)  reset - pin

// clk           (in)  clock - pini

input resetn, clk;

//

// interface to oc8051 cpu

//

// adr_i    (in)  address

// dat_o    (out) data output

// stb_i    (in)  strobe

// ack_o    (out) acknowledge

// cyc_i    (in)  cycle

input         stb_i,

              cyc_i;

input  [15:0] adr_i;

output        ack_o;

output [31:0] dat_o;

//

// interface to instruction rom

//

// adr_o    (out) address

// dat_i    (in)  data input

// stb_o    (out) strobe

// ack_i    (in) acknowledge

// cyc_o    (out)  cycle

input         ack_i;

input  [31:0] dat_i;

output        stb_o,

              cyc_o;

output [15:0] adr_o;

//

// internal bufers and wires

//

reg [15:0] adr_o;

reg        stb_o;

assign ack_o = ack_i;

assign dat_o = dat_i;

//assign stb_o = stb_i || ack_i;

assign cyc_o = stb_o;

//assign adr_o = ack_i ? adr : adr_i;

always @(posedge clk or negedge resetn)

  if (resetn == 1'b0) begin

    stb_o <= #1 1'b0;

    adr_o <= #1 16'h0000;

  end else if (ack_i) begin

    stb_o <= #1 stb_i;

    adr_o <= #1 adr_i;

  end else if (!stb_o & stb_i) begin

    stb_o <= #1 1'b1;

    adr_o <= #1 adr_i;

  end

endmodule