Subversion Repositories 8051

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

////                                                              ////

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

////                                                              ////

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

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

////                                                              ////

////  Description                                                 ////

////   program status word                                        ////

////                                                              ////

////  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                     ////

////                                                              ////

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

//

// ver: 1

//

// synopsys translate_off

`include "oc8051_timescale.v"

// synopsys translate_on

`include "oc8051_defines.v"

module oc8051_psw (clk, rst, wr_addr, rd_addr, data_in, wr, wr_bit, data_out, data_out_r, bit_out, p, cy_in, ac_in, ov_in, set);

//

// clk          (in)  clock

// rst          (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]

// data_out     (out) data output [oc8051_ram_sel.psw]

// data_out_r   (out) data output [oc8051_ram_sel.psw]

// 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, rst, wr, p, cy_in, ac_in, ov_in, wr_bit;

input [1:0] set;

input [2:0] rd_addr;

input [7:0] wr_addr, data_in;

output bit_out;

output [7:0] data_out;

output [7:0] data_out_r;

reg bit_out;

reg [7:0] data;

reg wr_psw_r;

wire wr_psw;

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

always @(posedge clk or posedge rst)

  if (rst) wr_psw_r <= #1 1'b0;

  else wr_psw_r <= #1 wr_psw;

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

assign data_out_r = wr_psw_r ? {data_in[7:1],p}:{data[7:1], p};

//

//case writing to psw

always @(posedge clk or posedge rst)

begin

  if (rst)

    data <= #1 `OC8051_RST_PSW;

//

// write to psw (byte addressable)

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

    data <= #1 data_in;

//

// write to psw (bit addressable)

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

    data[wr_addr[2:0]] <= #1 cy_in;

  else begin

    case (set)

      `OC8051_PS_CY: begin

//

//write carry

        data[7] <= #1 cy_in;

      end

      `OC8051_PS_OV: begin

//

//write carry and overflov

        data[7] <= #1 cy_in;

        data[2] <= #1 ov_in;

      end

      `OC8051_PS_AC:begin

//

//write carry, overflov and ac

        data[7] <= #1 cy_in;

        data[6] <= #1 ac_in;

        data[2] <= #1 ov_in;

      end

    endcase

  end

end

always @(posedge clk or posedge rst)

begin

  if (rst) bit_out <= #1 1'b0;

  else bit_out <= #1 data_out[rd_addr];

end

endmodule