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////  8051 cores acccumulator                                     ////

////                                                              ////

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

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

////                                                              ////

////  Description                                                 ////

////   accumulaor register 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 1.12  2003/04/09 16:24:03  simont

// change wr_sft to 2 bit wire.

//

// Revision 1.11  2003/04/09 15:49:42  simont

// Register oc8051_sfr dato output, add signal wait_data.

//

// Revision 1.10  2003/04/07 14:58:02  simont

// change sfr's interface.

//

// Revision 1.9  2003/01/13 14:14:40  simont

// replace some modules

//

// Revision 1.8  2002/11/05 17:23:54  simont

// add module oc8051_sfr, 256 bytes internal ram

//

// Revision 1.7  2002/09/30 17:33:59  simont

// prepared header

//

//

// synopsys translate_off

`include "oc8051_timescale.v"

// synopsys translate_on

`include "oc8051_defines.v"

module oc8051_acc (clk, rst,

                 bit_in, data_in, data2_in,

                 data_out,

                 wr, wr_bit, wr_addr,

                 p, wr_sfr);

input clk, rst, wr, wr_bit, bit_in;

input [1:0] wr_sfr;

input [7:0] wr_addr, data_in, data2_in;

output p;

output [7:0] data_out;

reg [7:0] data_out;

reg [7:0] acc;

wire wr_acc, wr2_acc, wr_bit_acc;

//

//calculates parity

assign p = ^acc;

assign wr_acc     = (wr_sfr==`OC8051_WRS_ACC1) | (wr & !wr_bit & (wr_addr==`OC8051_SFR_ACC));

assign wr2_acc    = (wr_sfr==`OC8051_WRS_ACC2);

assign wr_bit_acc = (wr & wr_bit & (wr_addr[7:3]==`OC8051_SFR_B_ACC));

//

//writing to acc

always @(wr_sfr or data2_in or wr2_acc or wr_acc or wr_bit_acc or wr_addr[2:0] or data_in or bit_in or data_out)

begin

  if (wr2_acc)

    acc = data2_in;

  else if (wr_acc)

    acc = data_in;

  else if (wr_bit_acc)

    case (wr_addr[2:0])

      3'b000: acc = {data_out[7:1], bit_in};

      3'b001: acc = {data_out[7:2], bit_in, data_out[0]};

      3'b010: acc = {data_out[7:3], bit_in, data_out[1:0]};

      3'b011: acc = {data_out[7:4], bit_in, data_out[2:0]};

      3'b100: acc = {data_out[7:5], bit_in, data_out[3:0]};

      3'b101: acc = {data_out[7:6], bit_in, data_out[4:0]};

      3'b110: acc = {data_out[7],   bit_in, data_out[5:0]};

      default: acc = {bit_in, data_out[6:0]};

    endcase

  else

    acc = data_out;

end

always @(posedge clk or posedge rst)

begin

  if (rst)

    data_out <= #1 `OC8051_RST_ACC;

  else

    data_out <= #1 acc;

end

`ifdef OC8051_SIMULATION

always @(data_out)

  if (data_out===8'hxx) begin

    $display("time ",$time, "   faulire: invalid write to ACC (oc8051_acc)");

#22

    $finish;

  end

`endif

endmodule