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/* $Id: fasm_tpsram.v,v 1.1 2008/06/05 20:51:56 sybreon Exp $

**

** FASM MEMORY LIBRARY

** Copyright (C) 2004-2009 Shawn Tan <shawn.tan@aeste.net>

** All rights reserved.

**

** FASM 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 3 of the

** License, or (at your option) any later version.

**

** FASM 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 FASM. If not, see <http:**www.gnu.org/licenses/>.

*/

/*

 * TWO PORT SYNCHRONOUS RAM - READ-BEFORE-WRITE

 * Synthesis proven on:

 * - Xilinx ISE

 * - Altera Quartus (>=8.0)

 */

module fasm_tpsram_rbw (/*AUTOARG*/

   // Outputs

   dat_o, xdat_o,

   // Inputs

   dat_i, adr_i, wre_i, stb_i, rst_i, clk_i, xdat_i, xadr_i, xwre_i,

   xstb_i, xrst_i, xclk_i

   );

   parameter AW = 8;  ///< address space (2^AW) words

   parameter DW = 32; ///< data word width bits

   // wishbone port a

   output [DW-1:0] dat_o; // DO

   input [DW-1:0]  dat_i; // DI - unused

   input [AW-1:0]  adr_i; // A

   input           wre_i; // WE - unused

   input           stb_i; // CS

   input           rst_i,

                   clk_i;

   // wishbone port x

   output [DW-1:0] xdat_o; // DO - unused

   input [DW-1:0]  xdat_i; // DI

   input [AW-1:0]  xadr_i; // A

   input           xwre_i; // WE

   input           xstb_i; // CS

   input           xrst_i,

                   xclk_i;

   // address latch

   reg [AW-1:0]    rA, rX;

   // memory block

   reg [DW-1:0]    bram [(1<<AW)-1:0];

   always @(posedge xclk_i)

     if (xstb_i)

       begin

          rX <= #1 bram[xadr_i];

       end

   always @(posedge clk_i)

     if (stb_i)

       begin

          rA <= #1 bram[adr_i];

          if (wre_i) // strobe and write-enable

            bram[adr_i] <= #1 dat_i;

       end

   assign          xdat_o = rX; // write-thru

   assign          dat_o = rA; // write-thru

   // ### SIMULATION ONLY ###

   // synopsys translate_off

   integer i;

   initial begin

      for (i=0; i<(1<<AW); i=i+1) begin

         bram[i] <= $random;

      end

   end

   // synopsys translate_on

endmodule // fasm_dpsram