Subversion Repositories oms8051mini

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////  8051 program status word                                    ////

////                                                              ////

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

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

////                                                              ////

////  Description                                                 ////

////   program status word                                        ////

////                                                              ////

////  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                 ////

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//// 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 1.11  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 14:14:41  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

//

//

`include "top_defines.v"

module oc8051_psw (clk, resetn, wr_addr, data_in, wr, wr_bit, data_out, p,

                cy_in, ac_in, ov_in, set, bank_sel);

//

// clk          (in)  clock

// resetn          (in)  reset

// addr         (in)  write address [oc8051_ram_wr_sel.out]

// data_in      (in)  data input [oc8051_alu.des1]

// wr           (in)  write [oc8051_decoder.wr -r]

// wr_bit       (in)  write bit addresable [oc8051_decoder.bit_addr -r]

// p            (in)  parity [oc8051_acc.p]

// cy_in        (in)  input bit data [oc8051_alu.desCy]

// ac_in        (in)  auxiliary carry input [oc8051_alu.desAc]

// ov_in        (in)  overflov input [oc8051_alu.desOv]

// set          (in)  set psw (write to caryy, carry and overflov or carry, owerflov and ac) [oc8051_decoder.psw_set -r]

//

input clk, resetn, wr, p, cy_in, ac_in, ov_in, wr_bit;

input [1:0] set;

input [7:0] wr_addr, data_in;

output [1:0] bank_sel;

output [7:0] data_out;

reg [7:1] data;

wire wr_psw;

assign wr_psw = (wr & (wr_addr==`OC8051_SFR_PSW) && !wr_bit);

assign bank_sel = wr_psw ? data_in[4:3]:data[4:3];

assign data_out = {data[7:1], p};

//

//case writing to psw

always @(posedge clk or negedge resetn)

begin

  if (resetn == 1'b0)

    data <= `OC8051_RST_PSW;

//

// write to psw (byte addressable)

  else begin

    if (wr & (wr_bit==1'b0) & (wr_addr==`OC8051_SFR_PSW))

      data[7:1] <= data_in[7:1];

//

// write to psw (bit addressable)

    else if (wr & wr_bit & (wr_addr[7:3]==`OC8051_SFR_B_PSW))

      data[wr_addr[2:0]] <= cy_in;

    else begin

      case (set) /* synopsys full_case parallel_case */

        `OC8051_PS_CY: begin

//

//write carry

          data[7] <= cy_in;

        end

        `OC8051_PS_OV: begin

//

//write carry and overflov

          data[7] <= cy_in;

          data[2] <= ov_in;

        end

        `OC8051_PS_AC:begin

//

//write carry, overflov and ac

          data[7] <= cy_in;

          data[6] <= ac_in;

          data[2] <= ov_in;

        end

      endcase

    end

  end

end

endmodule