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////  raminfr.v                                                   ////

////                                                              ////

////                                                              ////

////  This file is part of the "UART 16550 compatible" project    ////

////  http://www.opencores.org/cores/uart16550/                   ////

////                                                              ////

////  Documentation related to this project:                      ////

////  - http://www.opencores.org/cores/uart16550/                 ////

////                                                              ////

////  Projects compatibility:                                     ////

////  - WISHBONE                                                  ////

////  RS232 Protocol                                              ////

////  16550D uart (mostly supported)                              ////

////                                                              ////

////  Overview (main Features):                                   ////

////  Inferrable Distributed RAM for FIFOs                        ////

////                                                              ////

////  Known problems (limits):                                    ////

////  None                .                                       ////

////                                                              ////

////  To Do:                                                      ////

////  Nothing so far.                                             ////

////                                                              ////

////  Author(s):                                                  ////

////      - gorban@opencores.org                                  ////

////      - Jacob Gorban                                          ////

////                                                              ////

////  Created:        2002/07/22                                  ////

////  Last Updated:   2002/07/22                                  ////

////                  (See log for the revision history)          ////

////                                                              ////

////                                                              ////

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

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//// Copyright (C) 2000, 2001 Authors                             ////

////                                                              ////

//// 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: raminfr.v,v $

// Revision 1.2  2002/07/29 21:16:18  gorban

// The uart_defines.v file is included again in sources.

//

// Revision 1.1  2002/07/22 23:02:23  gorban

// Bug Fixes:

//  * Possible loss of sync and bad reception of stop bit on slow baud rates fixed.

//   Problem reported by Kenny.Tung.

//  * Bad (or lack of ) loopback handling fixed. Reported by Cherry Withers.

//

// Improvements:

//  * Made FIFO's as general inferrable memory where possible.

//  So on FPGA they should be inferred as RAM (Distributed RAM on Xilinx).

//  This saves about 1/3 of the Slice count and reduces P&R and synthesis times.

//

//  * Added optional baudrate output (baud_o).

//  This is identical to BAUDOUT* signal on 16550 chip.

//  It outputs 16xbit_clock_rate - the divided clock.

//  It's disabled by default. Define UART_HAS_BAUDRATE_OUTPUT to use.

//

//Following is the Verilog code for a dual-port RAM with asynchronous read. 

`include "uart_defines.v"

module raminfr

        (clk, we, a, dpra, di, dpo);

parameter addr_width = 4;

parameter data_width = 8;

parameter depth = 16;

input clk;

input we;

input  [addr_width-1:0] a;

input  [addr_width-1:0] dpra;

input  [data_width-1:0] di;

//output [data_width-1:0] spo;   

output [data_width-1:0] dpo;

reg    [data_width-1:0] ram [depth-1:0];

`ifdef SYNC_RAM

   reg [data_width-1:0] dpo;

`else

   wire [data_width-1:0] dpo;

`endif

wire  [data_width-1:0] di;

wire  [addr_width-1:0] a;

wire  [addr_width-1:0] dpra;

  always @(posedge clk) begin

    if (we)

      ram[a] <= di;

  end

`ifdef SYNC_RAM

   always @(negedge clk)

     dpo = ram[dpra];

`else

   assign dpo = ram[dpra];

`endif

endmodule