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

////                                                              ////

////  Tubo 8051 cores common library Module                       ////

////                                                              ////

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

////  http://www.opencores.org/cores/turbo8051/                   ////

////                                                              ////

////  Description                                                 ////

////  Turbo 8051 definitions.                                     ////

////                                                              ////

////  To Do:                                                      ////

////    nothing                                                   ////

////                                                              ////

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

////      - Dinesh Annayya, dinesha@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                     ////

////                                                              ////

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

/**********************************************

      Web-bone , Read from Memory and Write to WebBone External Memory

**********************************************/

module wb_wr_mem2mem (

              rst_n               ,

              clk                 ,

    // Master Interface Signal

              mem_taddr           ,

              mem_addr            ,

              mem_empty           ,

              mem_aempty          ,

              mem_rd              ,

              mem_dout            ,

              mem_eop             ,

              cfg_desc_baddr      ,

              desc_req            ,

              desc_ack            ,

              desc_disccard       ,

              desc_data           ,

    // Slave Interface Signal

              wbo_din             ,

              wbo_taddr           ,

              wbo_addr            ,

              wbo_be              ,

              wbo_we              ,

              wbo_ack             ,

              wbo_stb             ,

              wbo_cyc             ,

              wbo_err             ,

              wbo_rty

         );

parameter D_WD    = 16; // Data Width

parameter BE_WD   = 2;  // Byte Enable

parameter ADR_WD  = 28; // Address Width

parameter TAR_WD  = 4;  // Target Width

// State Machine

parameter   IDLE       = 2'h0;

parameter   XFR        = 2'h1;

parameter   DESC_WAIT  = 2'h2;

parameter   DESC_XFR   = 2'h3;

input               clk      ;  // CLK_I The clock input [CLK_I] coordinates all activities 

                                // for the internal logic within the WISHBONE interconnect. 

                                // All WISHBONE output signals are registered at the 

                                // rising edge of [CLK_I]. 

                                // All WISHBONE input signals must be stable before the 

                                // rising edge of [CLK_I]. 

input               rst_n    ;  // RST_I The reset input [RST_I] forces the WISHBONE interface 

                                // to restart. Furthermore, all internal self-starting state 

                                // machines will be forced into an initial state. 

//------------------------------------------

// Stanard Memory Interface

//------------------------------------------

input [TAR_WD-1:0]  mem_taddr;  // target address 

input [15:0]        mem_addr;   // memory address 

input               mem_empty;  // memory empty 

input               mem_aempty; // memory empty 

output              mem_rd;     // memory read

input  [7:0]        mem_dout;   // memory read data

input               mem_eop;    // Last Transfer indication

//----------------------------------------

// Discriptor defination

//----------------------------------------

input              desc_req;    // descriptor request

output             desc_ack;    // descriptor ack

input              desc_disccard;// descriptor discard

input [15:6]       cfg_desc_baddr;  // descriptor memory base address

input [31:0]       desc_data;   // descriptor data

//------------------------------------------

// External Memory WB Interface

//------------------------------------------

output [TAR_WD-1:0] wbo_taddr ;

output              wbo_stb  ; // STB_O The strobe output [STB_O] indicates a valid data 

                               // transfer cycle. It is used to qualify various other signals 

                               // on the interface such as [SEL_O(7..0)]. The SLAVE must 

                               // assert either the [ACK_I], [ERR_I] or [RTY_I] signals in 

                               // response to every assertion of the [STB_O] signal. 

output              wbo_we   ; // WE_O The write enable output [WE_O] indicates whether the 

                               // current local bus cycle is a READ or WRITE cycle. The 

                               // signal is negated during READ cycles, and is asserted 

                               // during WRITE cycles. 

input               wbo_ack  ; // The acknowledge input [ACK_I], when asserted, 

                               // indicates the termination of a normal bus cycle. 

                               // Also see the [ERR_I] and [RTY_I] signal descriptions. 

output [ADR_WD-1:0] wbo_addr  ; // The address output array [ADR_O(63..0)] is used 

                               // to pass a binary address, with the most significant 

                               // address bit at the higher numbered end of the signal array. 

                               // The lower array boundary is specific to the data port size. 

                               // The higher array boundary is core-specific. 

                               // In some cases (such as FIFO interfaces) 

                               // the array may not be present on the interface. 

output [BE_WD-1:0] wbo_be     ; // Byte Enable 

                               // SEL_O(7..0) The select output array [SEL_O(7..0)] indicates 

                               // where valid data is expected on the [DAT_I(63..0)] signal 

                               // array during READ cycles, and where it is placed on the 

                               // [DAT_O(63..0)] signal array during WRITE cycles. 

                               // Also see the [DAT_I(63..0)], [DAT_O(63..0)] and [STB_O] 

                               // signal descriptions.

output            wbo_cyc    ; // CYC_O The cycle output [CYC_O], when asserted, 

                               // indicates that a valid bus cycle is in progress. 

                               // The signal is asserted for the duration of all bus cycles. 

                               // For example, during a BLOCK transfer cycle there can be 

                               // multiple data transfers. The [CYC_O] signal is asserted 

                               // during the first data transfer, and remains asserted 

                               // until the last data transfer. The [CYC_O] signal is useful 

                               // for interfaces with multi-port interfaces 

                               // (such as dual port memories). In these cases, 

                               // the [CYC_O] signal requests use of a common bus from an 

                               // arbiter. Once the arbiter grants the bus to the MASTER, 

                               // it is held until [CYC_O] is negated. 

output [D_WD-1:0] wbo_din;     // DAT_I(63..0) The data input array [DAT_I(63..0)] is 

                               // used to pass binary data. The array boundaries are 

                               // determined by the port size. Also see the [DAT_O(63..0)] 

                               // and [SEL_O(7..0)] signal descriptions. 

input             wbo_err; // ERR_I The error input [ERR_I] indicates an abnormal 

                           // cycle termination. The source of the error, and the 

                           // response generated by the MASTER is defined by the IP core 

                           // supplier in the WISHBONE DATASHEET. Also see the [ACK_I] 

                           // and [RTY_I] signal descriptions. 

input             wbo_rty; // RTY_I The retry input [RTY_I] indicates that the indicates 

                           // that the interface is not ready to accept or send data, and 

                           // that the cycle should be retried. When and how the cycle is 

                           // retried is defined by the IP core supplier in the WISHBONE 

                           // DATASHEET. Also see the [ERR_I] and [RTY_I] signal 

                           // descriptions. 

//-------------------------------------------

// Register Dec

//-------------------------------------------

reg [TAR_WD-1:0]     wbo_taddr ;

reg [ADR_WD-1:0]     wbo_addr  ;

reg                  wbo_stb   ;

reg                  wbo_we    ;

reg [BE_WD-1:0]      wbo_be    ;

reg                  wbo_cyc   ;

reg [D_WD-1:0]       wbo_din   ;

reg [1:0]            state     ;

reg                  mem_rd    ;

reg [3:0]            desc_ptr  ; // descriptor pointer, in 32 bit mode

reg                  mem_eop_l ; // delayed eop signal

reg                  desc_ack  ; // delayed eop signal

always @(negedge rst_n or posedge clk) begin

   if(rst_n == 0) begin

      wbo_taddr <= 0;

      wbo_addr  <= 0;

      wbo_stb   <= 0;

      wbo_we    <= 0;

      wbo_be    <= 0;

      wbo_cyc   <= 0;

      wbo_din   <= 0;

      mem_rd    <= 0;

      desc_ptr  <= 0;

      mem_eop_l <= 0;

      desc_ack  <= 0;

      state     <= IDLE;

   end

   else begin

      case(state)

       IDLE: begin

          desc_ack <= 0;

          if(!mem_empty) begin

             wbo_taddr <= mem_taddr;

             wbo_addr  <= mem_addr[14:2];

             wbo_stb   <= 1'b1;

             wbo_we    <= 1'b1;

             wbo_be    <= 1 << mem_addr[1:0];

             wbo_cyc   <= 1;

             wbo_din   <= {mem_dout,mem_dout,mem_dout,mem_dout};

             mem_eop_l <= mem_eop;

             mem_rd    <= 1;

             state     <= XFR;

          end

       end

       XFR: begin

          if(wbo_ack) begin

             mem_eop_l <= mem_eop;

             wbo_addr  <= mem_addr[14:2];

             wbo_be    <= 1 << mem_addr[1:0];

             wbo_din   <= {mem_dout,mem_dout,mem_dout,mem_dout};

             if(mem_eop_l) begin

                state <= DESC_WAIT;

             end

             else if(mem_aempty || mem_empty) begin

                wbo_stb   <= 1'b0;

                wbo_cyc   <= 0;

                state     <= IDLE;

             end else begin

               mem_rd <= 1;

             end

          end else begin

             mem_rd <= 0;

          end

       end

       DESC_WAIT: begin

          if(desc_req) begin

             desc_ack    <= 1;

             if(desc_disccard) begin // if the Desc is discarded

                state     <= IDLE;

             end

             else begin

                wbo_addr  <= {cfg_desc_baddr[15:6],desc_ptr[3:0]}; // Each Transfer is 32bit

                wbo_be    <= 4'hF;

                wbo_din   <= desc_data;

                wbo_we    <= 1'b1;

                wbo_stb   <= 1'b1;

                wbo_cyc   <= 1;

                state     <= DESC_XFR;

                desc_ptr  <= desc_ptr+1;

             end

          end

       end

       DESC_XFR: begin

           desc_ack <= 0;

          if(wbo_ack) begin

              wbo_stb   <= 1'b0;

              wbo_cyc   <= 1'b0;

              state     <= IDLE;

          end

       end

      endcase

   end

end

endmodule