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

////                                                              ////

////  8051 data ram                                               ////

////                                                              ////

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

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

////                                                              ////

////  Description                                                 ////

////   data ram                                                   ////

////                                                              ////

////  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_ram_top (clk, rst, rd_addr, rd_data, wr_addr, bit_addr, wr_data, wr, bit_data_in, bit_data_out);

//

// clk          (in)  clock

// rd_addr      (in)  read addres [oc8051_ram_rd_sel.out]

// rd_data      (out) read data [oc8051_ram_sel.in_ram]

// wr_addr      (in)  write addres [oc8051_ram_wr_sel.out]

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

// wr_data      (in)  write data [oc8051_alu.des1]

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

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

// bit_data_out (out)  bit data output [oc8051_ram_sel.bit_in]

//

input clk, wr, bit_addr, bit_data_in, rst;

input [7:0] rd_addr, wr_addr, wr_data;

output bit_data_out;

output [7:0] rd_data;

// rd_addr_m    read address modified

// wr_addr_m    write address modified

// wr_data_m    write data modified

reg [7:0] rd_addr_m, wr_addr_m, wr_data_m;

// bit_addr_r   bit addresable instruction (registerd)

reg bit_addr_r;

reg [2:0] bit_select;

assign bit_data_out = rd_data[bit_select];

oc8051_ram oc8051_ram1(.clk(clk), .rd_addr(rd_addr_m), .rd_data(rd_data), .wr_addr(wr_addr_m),

         .wr_data(wr_data_m), .wr(wr));

always @(posedge clk)

  bit_addr_r <= #1 bit_addr;

always @(rd_addr or bit_addr)

begin

  case ({bit_addr, rd_addr[7]})

    2'b10: rd_addr_m = {4'b0010, rd_addr[6:3]};

    2'b11: rd_addr_m = {1'b1, rd_addr[6:3], 3'b000};

    default: rd_addr_m = rd_addr;

  endcase

end

always @(posedge clk)

  bit_select <= #1 rd_addr[2:0];

always @(wr_addr or bit_addr_r)

begin

  casex ({bit_addr_r, wr_addr[7]})

    2'b10: wr_addr_m = {4'b0010, wr_addr[6:3]};

    2'b11: wr_addr_m = {1'b1, wr_addr[6:3], 3'b000};

    default: wr_addr_m = wr_addr;

  endcase

end

always @(rd_data or bit_select or bit_data_in or wr_data or bit_addr_r)

begin

  if (bit_addr_r) begin

    case (bit_select)

      3'b000: wr_data_m = {rd_data[7:1], bit_data_in};

      3'b001: wr_data_m = {rd_data[7:2], bit_data_in, rd_data[0]};

      3'b010: wr_data_m = {rd_data[7:3], bit_data_in, rd_data[1:0]};

      3'b011: wr_data_m = {rd_data[7:4], bit_data_in, rd_data[2:0]};

      3'b100: wr_data_m = {rd_data[7:5], bit_data_in, rd_data[3:0]};

      3'b101: wr_data_m = {rd_data[7:6], bit_data_in, rd_data[4:0]};

      3'b110: wr_data_m = {rd_data[7], bit_data_in, rd_data[5:0]};

      default: wr_data_m = {bit_data_in, rd_data[6:0]};

    endcase

  end else

    wr_data_m = wr_data;

end

endmodule