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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OMS 8051 cores common library Module                        ////
////                                                              ////
////  This file is part of the OMS 8051 cores project             ////
////  http://www.opencores.org/cores/oms8051mini/                 ////
////                                                              ////
////  Description                                                 ////
////  OMS 8051 definitions.                                       ////
////                                                              ////
////  To Do:                                                      ////
////    nothing                                                   ////
////                                                              ////
////  Author(s):                                                  ////
////      - Dinesh Annayya, dinesha@opencores.org                 ////
////                                                              ////
////  Revision : Nov 26, 2016                                     //// 
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// 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 Wishbone Memory and Write to internal Memory
 
   This block handles following task
   1. Check the Descriptor Q for not empty
   2. If the Descriptor Q is not empty, the read the 32 bit descriptor
   3. The 32 bit descriptor holds following information
       [11:0]  - Packet Length
       [25:12] - MSB [15:2] of Packet Start Location
       [31:26] - Packet Status
   4. Based on the Packet Length, Read the data from external Data memory
      and write it to Internal Memory
 
**********************************************/
 
module wb_rd_mem2mem (
 
              rst_n               , 
              clk                 ,
 
    // descriptor handshake
              cfg_desc_baddr      ,
              desc_q_empty        ,
 
    // Master Interface Signal
              mem_taddr           ,
              mem_full            ,
              mem_afull           ,
              mem_wr              , 
              mem_din             ,
 
    // Slave Interface Signal
              wbo_dout            , 
              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
//--------------------
 
parameter IDLE         = 0;
parameter DESC_RD      = 1;
parameter DATA_WAIT    = 2;
parameter TXFR         = 3;
parameter MEM_WRITE2   = 4;
parameter MEM_WRITE3   = 5;
parameter MEM_WRITE4   = 6;
 
 
//-------------------------------------------
// Input Declaration
//------------------------------------------
 
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. 
 
//---------------------------------
// Descriptor Interface
//---------------------------------
input [15:6]   cfg_desc_baddr    ;  // descriptor Base Address
input          desc_q_empty      ; 
 
//------------------------------------------
// Stanard Memory Interface
//------------------------------------------
 
input [TAR_WD-1:0]  mem_taddr   ; // target address 
input               mem_full    ; // memory full
input               mem_afull   ; // memory afull 
output              mem_wr      ; // memory Write
output  [8:0]       mem_din     ; // memory read data
 
//------------------------------------------
// External Memory WB Interface
//------------------------------------------
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 [TAR_WD-1:0] wbo_taddr;
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. 
 
input [D_WD-1:0] wbo_dout;     // 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 Declration
//----------------------------------------
 
reg  [2:0]          state       ;
reg  [15:0]         cnt         ;
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 [15:0]          mem_addr    ;
 
 
 
 
reg [3:0]   desc_ptr;
reg [23:0]  tWrData; // Temp Write Data
reg [8:0]   mem_din;
reg         mem_wr;
 
always @(negedge rst_n or posedge clk) begin
   if(rst_n == 0) begin
      state       <= IDLE;
      wbo_taddr   <= 0;
      wbo_addr    <= 0;
      wbo_stb     <= 0;
      wbo_we      <= 0;
      wbo_be      <= 0;
      wbo_cyc     <= 0;
      desc_ptr    <= 0;
      mem_addr    <= 0;
      mem_din     <= 0;
      tWrData     <= 0;
      mem_wr      <= 0;
      cnt         <= 0;
   end
   else begin
      case(state)
         IDLE: begin
            mem_wr      <= 0;
            // Check for Descriptor Q not empty
            if(!desc_q_empty) begin
               wbo_taddr   <= mem_taddr;
               wbo_addr  <= {cfg_desc_baddr[15:6],desc_ptr[3:0]};
               wbo_be    <= 4'hF;
               wbo_we    <= 1'b0;
               wbo_stb   <= 1'b1;
               wbo_cyc   <= 1;
               state     <= DESC_RD;
               desc_ptr  <= desc_ptr+1;
            end
        end
       DESC_RD: begin
          // wait for web-bone ack
          if(wbo_ack) begin
              wbo_cyc   <= 1'b0;
              wbo_stb   <= 1'b0;
              state     <= IDLE;
              cnt       <= wbo_dout[11:0];
              mem_addr  <= {wbo_dout[27:12],2'b0};
              state     <= DATA_WAIT;
          end 
       end
 
         DATA_WAIT: begin
            mem_wr          <= 0; // Reset the write for handling interburst
            // check for internal memory not full and initiate
            // the transfer
            if(!(mem_full || mem_afull)) begin 
                wbo_taddr   <= mem_taddr;
                wbo_addr    <= mem_addr[14:2];
                wbo_stb     <= 1'b1;
                wbo_we      <= 1'b0;
                wbo_be      <= 4'hF;
                wbo_cyc     <= 1'b1;
                state       <= TXFR;
            end
         end
         TXFR: begin
            if(wbo_ack) begin
               wbo_cyc      <= 1'b0;
               wbo_stb      <= 1'b0;
               mem_addr     <= mem_addr+4;
               mem_din[7:0] <= wbo_dout[7:0]; // Write First Byte
               tWrData      <= wbo_dout[31:8];
               mem_din[8]   <= (cnt == 1) ? 1'b1 : 1'b0; // EOP generation at last transfer
               mem_wr       <= 1;
               cnt          <= cnt-1;
               if(cnt == 1) begin
                  state     <= IDLE;
               end else begin
                  state     <= MEM_WRITE2;
               end 
            end
         end
         MEM_WRITE2: begin // Write 2nd Byte
            if(!(mem_full || mem_afull)) begin // to handle the interburst fifo  full case
                mem_din[7:0] <= tWrData[7:0];
                mem_din[8]   <= (cnt == 1) ? 1'b1 : 1'b0; // EOP generation at last transfer
                mem_wr       <= 1;
                cnt          <= cnt-1;
                if(cnt == 1) begin
                   state     <= IDLE;
                end else begin
                  state     <= MEM_WRITE3;
                end 
            end else begin
               mem_wr        <= 0;
            end
         end 
         MEM_WRITE3: begin // Write 3rd Byte
            if(!(mem_full || mem_afull)) begin // to handle the interburst fifo  full case
                mem_din[7:0] <= tWrData[15:8];
                mem_din[8]   <= (cnt == 1) ? 1'b1 : 1'b0; // EOP generation at last transfer
                mem_wr       <= 1;
                cnt          <= cnt-1;
                if(cnt == 1) begin
                   state     <= IDLE;
                end else begin
                  state     <= MEM_WRITE4;
                end 
            end else begin
               mem_wr        <= 0;
            end
         end 
         MEM_WRITE4: begin // Write 4th Byte
            if(!(mem_full || mem_afull)) begin // to handle the interburst fifo  full case
                mem_din[7:0] <= tWrData[23:16];
                mem_din[8]   <= (cnt == 1) ? 1'b1 : 1'b0; // EOP generation at last transfer
                mem_wr       <= 1;
                cnt          <= cnt-1;
                if(cnt == 1) begin
                   state     <= IDLE;
                end else begin
                  state     <= DATA_WAIT;
                end 
            end else begin
               mem_wr        <= 0;
            end
         end 
         default: state       <= IDLE;
      endcase
   end
end
 
endmodule