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[/] [sdr_ctrl/] [trunk/] [rtl/] [wb2sdrc/] [wb2sdrc.v] - Rev 31

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/*********************************************************************
 
  This file is part of the sdram controller project           
  http://www.opencores.org/cores/sdr_ctrl/                    
 
  Description: WISHBONE to SDRAM Controller Bus Transalator
  This module translate the WISHBONE protocol to custom sdram controller i/f 
 
  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                     
 
*******************************************************************/
 
 
module wb2sdrc (
      // WB bus
      wb_rst_i           ,
      wb_clk_i           ,
 
      wb_stb_i           ,
      wb_ack_o           ,
      wb_addr_i          ,
      wb_we_i            ,
      wb_dat_i           ,
      wb_sel_i           ,
      wb_dat_o           ,
      wb_cyc_i           ,
      wb_cti_i           , 
 
 
      //SDRAM Controller Hand-Shake Signal 
      sdram_clk          ,
      sdram_resetn       ,
      sdr_req            ,
      sdr_req_addr       ,
      sdr_req_len        ,
      sdr_req_wr_n       ,
      sdr_req_ack        ,
      sdr_busy_n         ,
      sdr_wr_en_n        ,
      sdr_wr_next        ,
      sdr_rd_valid       ,
      sdr_last_rd        ,
      sdr_wr_data        ,
      sdr_rd_data        
 
      ); 
 
parameter      dw              = 32;  // data width
parameter      tw              = 8;   // tag id width
parameter      bl              = 9;   // burst_lenght_width 
//--------------------------------------
// Wish Bone Interface
// -------------------------------------      
input           wb_rst_i           ;
input           wb_clk_i           ;
 
input           wb_stb_i           ;
output          wb_ack_o           ;
input [29:0]    wb_addr_i          ;
input           wb_we_i            ; // 1 - Write, 0 - Read
input [dw-1:0]  wb_dat_i           ;
input [dw/8-1:0]wb_sel_i           ; // Byte enable
output [dw-1:0] wb_dat_o           ;
input           wb_cyc_i           ;
input  [2:0]    wb_cti_i           ;
/***************************************************
The Cycle Type Idenfier [CTI_IO()] Address Tag provides 
additional information about the current cycle. 
The MASTER sends this information to the SLAVE. The SLAVE can use this
information to prepare the response for the next cycle.
Table 4-2 Cycle Type Identifiers
CTI_O(2:0) Description
000 Classic cycle.
001 Constant address burst cycle
010 Incrementing burst cycle
011 Reserved
100 Reserved
101 Reserved
110 Reserved
111 End-of-Burst
****************************************************/
//--------------------------------------------
// SDRAM controller Interface 
//--------------------------------------------
input                   sdram_clk           ; // sdram clock
input                   sdram_resetn        ; // sdram reset
output                  sdr_req            ; // SDRAM request
output [29:0]           sdr_req_addr       ; // SDRAM Request Address
output [bl-1:0]         sdr_req_len        ;
output                  sdr_req_wr_n       ; // 0 - Write, 1 -> Read
input                   sdr_req_ack        ; // SDRAM request Accepted
input                   sdr_busy_n         ; // 0 -> sdr busy
output [dw/8-1:0]       sdr_wr_en_n        ; // Active low sdr byte-wise write data valid
input                   sdr_wr_next        ; // Ready to accept the next write
input                   sdr_rd_valid       ; // sdr read valid
input                   sdr_last_rd        ; // Indicate last Read of Burst Transfer
output [dw-1:0]         sdr_wr_data        ; // sdr write data
input  [dw-1:0]         sdr_rd_data        ; // sdr read data
 
//----------------------------------------------------
// Wire Decleration
// ---------------------------------------------------
wire                    cmdfifo_full;
wire                    cmdfifo_empty;
wire                    wrdatafifo_full;
wire                    wrdatafifo_empty;
wire                    tagfifo_full;
wire                    tagfifo_empty;
wire                    rddatafifo_empty;
wire                    rddatafifo_full;
 
reg                     pending_read;
 
 
// Generate Address Enable only when internal fifo (Address + data are not full
 
assign wb_ack_o = (wb_stb_i && wb_cyc_i && wb_we_i) ?  // Write Phase
	                  ((!cmdfifo_full) && (!wrdatafifo_full)) :
		  (wb_stb_i && wb_cyc_i && !wb_we_i) ? // Read Phase 
		           !rddatafifo_empty : 1'b0;
 
// Accept the cmdfifo only when burst start + address enable + address
// valid is asserted
wire           cmdfifo_wr   = (wb_stb_i && wb_cyc_i && wb_we_i) ? wb_ack_o :
	                      (wb_stb_i && wb_cyc_i && !wb_we_i) ? !pending_read: 1'b0 ; 
wire           cmdfifo_rd   = sdr_req_ack;
assign         sdr_req      = !cmdfifo_empty;
 
wire [bl-1:0]  burst_length  = 1;  // 0 Mean 1 Transfer
 
always @(posedge wb_rst_i or posedge wb_clk_i) begin
   if(wb_rst_i) begin
       pending_read <= 1'b0;
   end else begin
      pending_read <=  wb_stb_i & wb_cyc_i & !wb_we_i & !wb_ack_o;
   end
end
 
   // Address + Burst Length + W/R Request 
    async_fifo #(.W(30+bl+1),.DP(4)) u_cmdfifo (
     // Write Path Sys CLock Domain
          .wr_clk     (wb_clk_i),
          .wr_reset_n (!wb_rst_i),
          .wr_en      (cmdfifo_wr),
          .wr_data    ({burst_length,
	                !wb_we_i,
		       wb_addr_i}),
          .afull      (),
          .full       (cmdfifo_full),
 
     // Read Path, SDRAM clock domain
          .rd_clk     (sdram_clk),
          .rd_reset_n (sdram_resetn),
          .aempty     (),
          .empty      (cmdfifo_empty),
          .rd_en      (cmdfifo_rd),
          .rd_data    ({sdr_req_len,
	             sdr_req_wr_n,
		     sdr_req_addr})
     );
 
// synopsys translate_off
always @(posedge wb_clk_i) begin
  if (cmdfifo_full == 1'b1 && cmdfifo_wr == 1'b1)  begin
     $display("ERROR:%m COMMAND FIFO WRITE OVERFLOW");
  end 
end 
// synopsys translate_off
always @(posedge sdram_clk) begin
   if (cmdfifo_empty == 1'b1 && cmdfifo_rd == 1'b1) begin
      $display("ERROR:%m COMMAND FIFO READ OVERFLOW");
   end
end 
// synopsys translate_on
 
 
wire  wrdatafifo_wr  = wb_ack_o & wb_we_i ;
wire  wrdatafifo_rd  = sdr_wr_next;
 
 
   // Write DATA + Data Mask FIFO
    async_fifo #(.W(dw+(dw/8)), .DP(16)) u_wrdatafifo (
       // Write Path , System clock domain
          .wr_clk     (wb_clk_i),
          .wr_reset_n (!wb_rst_i),
          .wr_en   (wrdatafifo_wr),
          .wr_data ({~wb_sel_i,
	             wb_dat_i}),
          .afull    (),
          .full     (wrdatafifo_full),
 
 
       // Read Path , SDRAM clock domain
          .rd_clk     (sdram_clk),
          .rd_reset_n (sdram_resetn),
          .aempty     (),
          .empty      (wrdatafifo_empty),
          .rd_en      (wrdatafifo_rd),
          .rd_data    ({sdr_wr_en_n,
                        sdr_wr_data})
     );
// synopsys translate_off
always @(posedge wb_clk_i) begin
  if (wrdatafifo_full == 1'b1 && wrdatafifo_wr == 1'b1)  begin
     $display("ERROR:%m WRITE DATA FIFO WRITE OVERFLOW");
  end 
end 
 
always @(posedge sdram_clk) begin
   if (wrdatafifo_empty == 1'b1 && wrdatafifo_rd == 1'b1) begin
      $display("ERROR:%m WRITE DATA FIFO READ OVERFLOW");
   end
end 
// synopsys translate_on
 
// -------------------------------------------------------------------
//  READ DATA FIFO
//  ------------------------------------------------------------------
wire    rd_eop; // last read indication
wire    rddatafifo_wr = sdr_rd_valid;
wire    rddatafifo_rd = wb_ack_o & !wb_we_i & (rddatafifo_empty == 0);
 
   // READ DATA FIFO depth is kept small, assuming that Sys-CLock > SDRAM Clock
   // READ DATA + EOP
    async_fifo #(.W(dw+1), .DP(4)) u_rddatafifo (
       // Write Path , SDRAM clock domain
          .wr_clk     (sdram_clk),
          .wr_reset_n (sdram_resetn),
          .wr_en      (rddatafifo_wr),
          .wr_data    ({sdr_last_rd,
	                sdr_rd_data}),
          .afull      (),
          .full       (rddatafifo_full),
 
 
       // Read Path , SYS clock domain
          .rd_clk     (wb_clk_i),
          .rd_reset_n (!wb_rst_i),
          .empty      (rddatafifo_empty),
          .aempty     (),
          .rd_en      (rddatafifo_rd),
          .rd_data    ({rd_eop,
                        wb_dat_o})
     );
 
// synopsys translate_off
always @(posedge sdram_clk) begin
  if (rddatafifo_full == 1'b1 && rddatafifo_wr == 1'b1)  begin
     $display("ERROR:%m READ DATA FIFO WRITE OVERFLOW");
  end 
end 
 
always @(posedge wb_clk_i) begin
   if (rddatafifo_empty == 1'b1 && rddatafifo_rd == 1'b1) begin
      $display("ERROR:%m READ DATA FIFO READ OVERFLOW");
   end
end 
// synopsys translate_on
 
 
endmodule
 

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