Subversion Repositories i650

`timescale 1ns / 1ps

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

// IBM 650 Reconstruction in Verilog (i650)

// 

// This file is part of the IBM 650 Reconstruction in Verilog (i650) project

// http:////www.opencores.org/project,i650

//

// Description:

//   Convert dynamic portion of 650 address into a word offset in general

//   storage RAM.

// 

// Additional Comments: 

//

// Copyright (c) 2015 Robert Abeles

//

// 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

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

module ram_word_offset (

   input [0:6] addr_t, addr_u,

   output reg  [0:14] offset

   );

   always @(*) begin

      case({addr_t[2:6], addr_u})

         12'b00001_01_00001: offset = 15'd0;

         12'b00001_01_00010: offset = 15'd12;

         12'b00001_01_00100: offset = 15'd24;

         12'b00001_01_01000: offset = 15'd36;

         12'b00001_01_10000: offset = 15'd48;

         12'b00001_10_00001: offset = 15'd60;

         12'b00001_10_00010: offset = 15'd72;

         12'b00001_10_00100: offset = 15'd84;

         12'b00001_10_01000: offset = 15'd96;

         12'b00001_10_10000: offset = 15'd108;

         12'b00010_01_00001: offset = 15'd120;

         12'b00010_01_00010: offset = 15'd132;

         12'b00010_01_00100: offset = 15'd144;

         12'b00010_01_01000: offset = 15'd156;

         12'b00010_01_10000: offset = 15'd168;

         12'b00010_10_00001: offset = 15'd180;

         12'b00010_10_00010: offset = 15'd192;

         12'b00010_10_00100: offset = 15'd204;

         12'b00010_10_01000: offset = 15'd216;

         12'b00010_10_10000: offset = 15'd228;

         12'b00100_01_00001: offset = 15'd240;

         12'b00100_01_00010: offset = 15'd252;

         12'b00100_01_00100: offset = 15'd264;

         12'b00100_01_01000: offset = 15'd276;

         12'b00100_01_10000: offset = 15'd288;

         12'b00100_10_00001: offset = 15'd300;

         12'b00100_10_00010: offset = 15'd312;

         12'b00100_10_00100: offset = 15'd324;

         12'b00100_10_01000: offset = 15'd336;

         12'b00100_10_10000: offset = 15'd348;

         12'b01000_01_00001: offset = 15'd360;

         12'b01000_01_00010: offset = 15'd372;

         12'b01000_01_00100: offset = 15'd384;

         12'b01000_01_01000: offset = 15'd396;

         12'b01000_01_10000: offset = 15'd408;

         12'b01000_10_00001: offset = 15'd420;

         12'b01000_10_00010: offset = 15'd432;

         12'b01000_10_00100: offset = 15'd444;

         12'b01000_10_01000: offset = 15'd456;

         12'b01000_10_10000: offset = 15'd468;

         12'b10000_01_00001: offset = 15'd480;

         12'b10000_01_00010: offset = 15'd492;

         12'b10000_01_00100: offset = 15'd504;

         12'b10000_01_01000: offset = 15'd516;

         12'b10000_01_10000: offset = 15'd528;

         12'b10000_10_00001: offset = 15'd540;

         12'b10000_10_00010: offset = 15'd552;

         12'b10000_10_00100: offset = 15'd564;

         12'b10000_10_01000: offset = 15'd576;

         12'b10000_10_10000: offset = 15'd588;

         default:      offset = 15'd0;

      endcase;

   end;

endmodule