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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

  The 2Mx32 SDRAM is addressed by a 21 bit address,

  each loation is 32 bits wide.

  This 21 bit address is mapped as follows:

  ADDR [7:0]      : Column Address (256 columns)

  ADDR [18:8]     : Row Address (2K Rows)

  ADDR [20:19]    : Bank Address (2 banks)

  The 4Mx16 SDRAM is addressed by a 22 bit address,

  each loation is 16 bits wide.

  This 22 bit address is mapped as follows:

  ADDR [7:0]      : Column Address (256 columns)

  ADDR [21:10]    : Row Address (4K Rows)

  ADDR [21:20]    : Bank Address (4 banks)

  The 8Mx16 SDRAM is addressed by a 23 bit address,

  each loation is 16 bits wide.

  This 23 bit address is mapped as follows:

  ADDR [8:0]      : Column Address (512 columns)

  ADDR [20:9]     : Row Address (4K Rows)

  ADDR [22:21]    : Bank Address (4 banks)

  The SDRAMs are operated in 4 beat burst mode.

  This module takes requests from the mc,

  chops them to page boundaries if wrap=0,

  and passes the request to bank_ctl

  To Do:

    nothing

  Author(s):

      - Dinesh Annayya, dinesha@opencores.org

  Version  : 1.0 - 8th Jan 2012

 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.def"

module sdrc_req_gen (clk,

                    reset_n,

                    /* Request from app */

                    req,        // Transfer Request

                    req_id,     // ID for this transfer

                    req_addr,   // SDRAM Address

                    req_addr_mask,

                    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

                    sdr_core_busy_n,    // SDRAM Core Busy Indication

                    cfg_colbits,

                    /* Req to bank_ctl */

                    r2x_idle,

                    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,

                    sdr_width,

                    sdr_init_done);

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

   input                        clk, 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;

   input [`SDR_REQ_ID_W-1:0]     req_id;

   input [APP_AW:0]      req_addr;

   input [APP_AW-2:0]    req_addr_mask;

   input [APP_RW-1:0]    req_len;

   input                        req_wr_n, req_wrap;

   output                       req_ack, sdr_core_busy_n;

   /* Req to bank_ctl */

   output                       r2x_idle, r2b_req, r2b_start, r2b_last,

                                r2b_write, r2b_wrap;

   output [`SDR_REQ_ID_W-1:0]    r2b_req_id;

   output [1:0]          r2b_ba;

   output [11:0]                 r2b_raddr;

   output [11:0]                 r2b_caddr;

   output [APP_RW-1:0]   r2b_len;

   input                        b2r_ack, b2r_arb_ok, sdr_init_done;

//

   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 [APP_RW-1:0]      lcl_req_len;

   wire                         r2b_last, page_ovflw;

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

   wire [APP_RW:0]       max_r2b_len;

   wire [1:0]                    r2b_ba;

   wire [11:0]                   r2b_raddr;

   wire [11:0]                   r2b_caddr;

   reg [APP_AW-1:0]      curr_sdr_addr, sdr_addrs_mask;

   wire [APP_AW-1:0]     next_sdr_addr, next_sdr_addr1;

   //

   // The maximum length for no page overflow is 200h/100h - caddr. Split a request

   // into 2 or more requests if it crosses a page boundary.

   // For non-queue accesses req_addr_mask is set to all 1 and the accesses

   // proceed linearly. 

   // All queues end on a 512 byte boundary (actually a 1K boundary). For Q

   // accesses req_addr_mask is set to LSB of 1 and MSB of 0 to constrain the

   // accesses within the space for a Q. When splitting and calculating the next

   // address only the LSBs are incremented, the MSBs remain = req_addr.

   //

   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);

   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_addr1 = curr_sdr_addr + r2b_len;

   // Wrap back based on the mask

   assign next_sdr_addr = (sdr_addrs_mask & next_sdr_addr1) |

                          (~sdr_addrs_mask & curr_sdr_addr);

   assign sdr_core_busy_n = req_idle & b2r_arb_ok & sdr_init_done;

   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  :

                   (req_ld) ? next_req_len : lcl_req_len;

      curr_sdr_addr <= (req_ack) ? req_addr :

                       (req_ld) ? next_sdr_addr : curr_sdr_addr;

      sdr_addrs_mask <= (req_ack) ?((sdr_width == 2'b00)  ? req_addr_mask :

                                    (sdr_width == 2'b01)  ? {req_addr_mask,req_addr_mask[0]} :

                                                            {req_addr_mask,req_addr_mask[1:0]}) : sdr_addrs_mask;

   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

//

// Bank Bits are always - 2 Bits

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

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

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

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

   *  Colbits Mapping:

   *           2'b00 - 8 Bit

   *           2'b01 - 16 Bit

   *           2'b10 - 10 Bit

   *           2'b11 - 11 Bits

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

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

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

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

   assign r2b_raddr = (cfg_colbits == 2'b00)  ? curr_sdr_addr[21:10] :

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

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

endmodule // sdr_req_gen