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

//

// Filename:    memdev.v

//

// Project:     OpenArty, an entirely open SoC based upon the Arty platform

//

// Purpose:     This file is really simple: it creates an on-chip memory,

//              accessible via the wishbone bus, that can be used in this

//      project.  The memory has single cycle pipeline access, although the

//      memory pipeline here still costs a cycle and there may be other cycles

//      lost between the ZipCPU (or whatever is the master of the bus) and this,

//      thus costing more cycles in access.  Either way, operations can be

//      pipelined for single cycle access on subsequent transactions.

//

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

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

//

// Copyright (C) 2015-2016, Gisselquist Technology, LLC

//

// This program is free software (firmware): you can redistribute it and/or

// modify it under the terms of  the GNU General Public License as published

// by the Free Software Foundation, either version 3 of the License, or (at

// your option) any later version.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

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

//

//

module  memdev(i_clk, i_wb_cyc, i_wb_stb, i_wb_we, i_wb_addr, i_wb_data,

                o_wb_ack, o_wb_stall, o_wb_data);

        parameter       AW=15, DW=32;

        input                           i_clk, i_wb_cyc, i_wb_stb, i_wb_we;

        input           [(AW-1):0]       i_wb_addr;

        input           [(DW-1):0]       i_wb_data;

        output  reg                     o_wb_ack;

        output  wire                    o_wb_stall;

        output  reg     [(DW-1):0]       o_wb_data;

        reg             last_wstb, last_stb;

        always @(posedge i_clk)

                last_wstb <= (i_wb_stb)&&(i_wb_we);

        always @(posedge i_clk)

                last_stb <= (i_wb_stb);

        reg     [(DW-1):0]       last_data;

        reg     [(AW-1):0]       last_addr;

        always @(posedge i_clk)

                last_data <= i_wb_data;

        always @(posedge i_clk)

                last_addr <= i_wb_addr;

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

        always @(posedge i_clk)

                o_wb_data <= mem[last_addr];

        always @(posedge i_clk)

                if (last_wstb)

                        mem[last_addr] <= last_data;

        always @(posedge i_clk)

                o_wb_ack <= (last_stb);

        assign  o_wb_stall = 1'b0;

endmodule