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

  SDRAM Controller Request Generation

  This file is part of the sdram controller project

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

  Description: SDRAM Controller Reguest Generation

  Address Generation Based on cfg_colbits

     cfg_colbits= 2'b00

            Address[7:0]    - Column Address

            Address[9:8]    - Bank Address

            Address[21:10]  - Row Address

     cfg_colbits= 2'b01

            Address[8:0]    - Column Address

            Address[10:9]   - Bank Address

            Address[22:11]  - Row Address

     cfg_colbits= 2'b10

            Address[9:0]    - Column Address

            Address[11:10]   - Bank Address

            Address[23:12]  - Row Address

     cfg_colbits= 2'b11

            Address[10:0]    - Column Address

            Address[12:11]   - Bank Address

            Address[24:13]  - Row Address

  The SDRAMs are operated in 4 beat burst mode.

  If Wrap = 0;

      If the current burst cross the page boundary, then this block split the request into two coressponding change in address and request length

  if the current burst cross the page boundar.

  This module takes requests from the memory controller,

  chops them to page boundaries if wrap=0,

  and passes the request to bank_ctl

  Note: With Wrap = 0, each request from Application layer will be splited into two request,

        if the current burst cross the page boundary.

  To Do:

    nothing

  Author(s):

      - Dinesh Annayya, dinesha@opencores.org

  Version  : 0.0 - 8th Jan 2012

             0.1 - 5th Feb 2012, column/row/bank address are register to improve the timing issue in FPGA synthesis

 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

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

`include "sdrc_define.v"

module sdrc_req_gen (clk,

                    reset_n,

                    cfg_colbits,

                    sdr_width,

                    /* Request from app */

                    req,                // Transfer Request

                    req_id,             // ID for this transfer

                    req_addr,           // SDRAM Address

                    req_len,            // Burst Length (in 32 bit words)

                    req_wrap,           // Wrap mode request (xfr_len = 4)

                    req_wr_n,           // 0 => Write request, 1 => read req

                    req_ack,            // Request has been accepted

                    /* Req to xfr_ctl */

                    r2x_idle,

                    /* Req to bank_ctl */

                    r2b_req,            // request

                    r2b_req_id,         // ID

                    r2b_start,          // First chunk of burst

                    r2b_last,           // Last chunk of burst

                    r2b_wrap,           // Wrap Mode

                    r2b_ba,             // bank address

                    r2b_raddr,          // row address

                    r2b_caddr,          // col address

                    r2b_len,            // length

                    r2b_write,          // write request

                    b2r_ack,

                    b2r_arb_ok

                    );

parameter  APP_AW   = 30;  // Application Address Width

parameter  APP_DW   = 32;  // Application Data Width 

parameter  APP_BW   = 4;   // Application Byte Width

parameter  APP_RW   = 9;   // Application Request Width

parameter  SDR_DW   = 16;  // SDR Data Width 

parameter  SDR_BW   = 2;   // SDR Byte Width

parameter  REQ_BW   = 12;   //  Request Width

input                   clk           ;

input                   reset_n       ;

input [1:0]             cfg_colbits   ; // 2'b00 - 8 Bit column address, 2'b01 - 9 Bit, 10 - 10 bit, 11 - 11Bits

/* Request from app */

input                   req           ; // Request 

input [`SDR_REQ_ID_W-1:0] req_id      ; // Request ID

input [APP_AW-1:0]       req_addr      ; // Request Address

input [APP_RW-1:0]       req_len       ; // Request length

input                   req_wr_n      ; // 0 -Write, 1 - Read

input                   req_wrap      ; // 1 - Wrap the Address on page boundary

output                  req_ack       ; // Request Ack

/* Req to bank_ctl */

output                  r2x_idle      ;

output                  r2b_req       ; // Request

output                  r2b_start     ; // First Junk of the Burst Access

output                  r2b_last      ; // Last Junk of the Burst Access

output                  r2b_write     ; // 1 - Write, 0 - Read

output                  r2b_wrap      ; // 1 - Wrap the Address at the page boundary.

output [`SDR_REQ_ID_W-1:0]       r2b_req_id;

output [1:0]             r2b_ba        ; // Bank Address

output [11:0]            r2b_raddr     ; // Row Address

output [11:0]            r2b_caddr     ; // Column Address

output [REQ_BW-1:0]      r2b_len       ; // Burst Length

input                   b2r_ack       ; // Request Ack

input                   b2r_arb_ok    ; // Bank controller fifo is not full and ready to accept the command

//

input [1:0]              sdr_width; // 2'b00 - 32 Bit, 2'b01 - 16 Bit, 2'b1x - 8Bit

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

   // Internal Nets

   `define REQ_IDLE        1'b0

   `define REQ_ACTIVE      1'b1

   reg                  req_st, next_req_st;

   reg                  r2x_idle, req_ack, r2b_req, r2b_start,

                        r2b_write, req_idle, req_ld, lcl_wrap;

   reg [`SDR_REQ_ID_W-1:0]       r2b_req_id;

   reg [REQ_BW-1:0]      lcl_req_len;

   wire                 r2b_last, page_ovflw;

   wire [REQ_BW-1:0]     r2b_len, next_req_len;

   wire [REQ_BW:0]       max_r2b_len;

   reg [1:0]             r2b_ba;

   reg [11:0]            r2b_raddr;

   reg [11:0]            r2b_caddr;

   reg [APP_AW-1:0]      curr_sdr_addr ;

   wire [APP_AW-1:0]     next_sdr_addr ;

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

// Generate the internal Adress and Burst length Based on sdram width

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

reg [APP_AW:0]           req_addr_int;

reg [APP_RW-1:0]         req_len_int;

always @(*) begin

   if(sdr_width == 2'b00) begin // 32 Bit SDR Mode

      req_addr_int     = {1'b0,req_addr};

      req_len_int      = req_len;

   end else if(sdr_width == 2'b01) begin // 16 Bit SDR Mode

      // Changed the address and length to match the 16 bit SDR Mode

      req_addr_int     = {req_addr,1'b0};

      req_len_int      = {req_len,1'b0};

   end else  begin // 8 Bit SDR Mode

      // Changed the address and length to match the 16 bit SDR Mode

      req_addr_int    = {req_addr,2'b0};

      req_len_int     = {req_len,2'b0};

   end

end

   //

   // Identify the page over flow.

   // Find the Maximum Burst length allowed from the selected column

   // address, If the requested burst length is more than the allowed Maximum

   // burst length, then we need to handle the bank cross over case and we

   // need to split the reuest.

   //

   assign max_r2b_len = (cfg_colbits == 2'b00) ? (12'h100 - r2b_caddr) :

                        (cfg_colbits == 2'b01) ? (12'h200 - r2b_caddr) :

                        (cfg_colbits == 2'b10) ? (12'h400 - r2b_caddr) : (12'h800 - r2b_caddr);

     // If the wrap = 0 and current application burst length is crossing the page boundary, 

     // then request will be split into two with corresponding change in request address and request length.

     //

     // If the wrap = 0 and current burst length is not crossing the page boundary, 

     // then request from application layer will be transparently passed on the bank control block.

     //

     // if the wrap = 1, then this block will not modify the request address and length. 

     // The wrapping functionality will be handle by the bank control module and 

     // column address will rewind back as follows XX -> FF ? 00 ? 1

     //

     // Note: With Wrap = 0, each request from Application layer will be spilited into two request, 

     // if the current burst cross the page boundary. 

   assign page_ovflw = ({1'b0, lcl_req_len} > max_r2b_len) ? ~lcl_wrap : 1'b0;

   assign r2b_len = (page_ovflw) ? max_r2b_len : lcl_req_len;

   assign next_req_len = lcl_req_len - r2b_len;

   assign next_sdr_addr = curr_sdr_addr + r2b_len;

   assign r2b_wrap = lcl_wrap;

   assign r2b_last = ~page_ovflw;

//

//

//

   always @ (posedge clk) begin

      r2b_start      <= (req_ack) ? 1'b1 :

                        (b2r_ack) ? 1'b0 : r2b_start;

      r2b_write      <= (req_ack) ? ~req_wr_n : r2b_write;

      r2b_req_id     <= (req_ack) ? req_id : r2b_req_id;

      lcl_wrap       <= (req_ack) ? req_wrap : lcl_wrap;

      lcl_req_len    <= (req_ack) ? req_len_int  :

                        (req_ld) ? next_req_len : lcl_req_len;

      curr_sdr_addr  <= (req_ack) ? req_addr_int :

                        (req_ld) ? next_sdr_addr : curr_sdr_addr;

   end // always @ (posedge clk)

   always @ (*) begin

      case (req_st)      // synopsys full_case parallel_case

        `REQ_IDLE : begin

           r2x_idle = ~req;

           req_idle = 1'b1;

           req_ack = req & b2r_arb_ok;

           req_ld = 1'b0;

           r2b_req = 1'b0;

           next_req_st = (req & b2r_arb_ok) ? `REQ_ACTIVE : `REQ_IDLE;

        end // case: `REQ_IDLE

        `REQ_ACTIVE : begin

           r2x_idle = 1'b0;

           req_idle = 1'b0;

           req_ack = 1'b0;

           req_ld = b2r_ack;

           r2b_req = 1'b1;                       // req_gen to bank_req

           next_req_st = (b2r_ack & r2b_last) ? `REQ_IDLE : `REQ_ACTIVE;

        end // case: `REQ_ACTIVE

      endcase // case(req_st)

   end // always @ (req_st or ....)

   always @ (posedge clk)

      if (~reset_n) begin

         req_st <= `REQ_IDLE;

      end // if (~reset_n)

      else begin

         req_st <= next_req_st;

      end // else: !if(~reset_n)

//

// addrs bits for the bank, row and column

//

// Register row/column/bank to improve fpga timing issue

wire [APP_AW-1:0]        map_address ;

assign      map_address  = (req_ack) ? req_addr_int :

                           (req_ld)  ? next_sdr_addr : curr_sdr_addr;

always @ (posedge clk) begin

// Bank Bits are always - 2 Bits

    r2b_ba <= (cfg_colbits == 2'b00) ? {map_address[9:8]}   :

              (cfg_colbits == 2'b01) ? {map_address[10:9]}  :

              (cfg_colbits == 2'b10) ? {map_address[11:10]} : map_address[12:11];

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

*  Colbits Mapping:

*           2'b00 - 8 Bit

*           2'b01 - 16 Bit

*           2'b10 - 10 Bit

*           2'b11 - 11 Bits

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

    r2b_caddr <= (cfg_colbits == 2'b00) ? {4'b0, map_address[7:0]} :

                 (cfg_colbits == 2'b01) ? {3'b0, map_address[8:0]} :

                 (cfg_colbits == 2'b10) ? {2'b0, map_address[9:0]} : {1'b0, map_address[10:0]};

    r2b_raddr <= (cfg_colbits == 2'b00)  ? map_address[21:10] :

                 (cfg_colbits == 2'b01)  ? map_address[22:11] :

                 (cfg_colbits == 2'b10)  ? map_address[23:12] : map_address[24:13];

end

endmodule // sdr_req_gen