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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                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// 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 1.13  2003/06/03 17:16:16  simont
// `ifdef added.
//
// 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]) /* synopsys full_case parallel_case */
      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]};
      3'b111: 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