Subversion Repositories sdr_ctrl

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

  SDRAM Controller Transfer control

  This file is part of the sdram controller project

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

  Description: SDRAM Controller Transfer control

  This module takes requests from sdrc_bank_ctl and runs the

  transfer. The input request is guaranteed to be in a bank that is

  precharged and activated. This block runs the transfer until a

  burst boundary is reached, then issues another read/write command

  to sequentially step thru memory if wrap=0, until the transfer is

  completed.

  if a read transfer finishes and the caddr is not at a burst boundary

  a burst terminate command is issued unless another read/write or

  precharge to the same bank is pending.

  if a write transfer finishes and the caddr is not at a burst boundary

  a burst terminate command is issued unless a read/write is pending.

   If a refresh request is made, the bank_ctl will be held off until

   the number of refreshes requested are completed.

   This block also handles SDRAM initialization.

  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_define.v"

module sdrc_xfr_ctl (clk,

                    reset_n,

                    /* Transfer request from bank_ctl */

                    r2x_idle,      // Req is idle

                    b2x_idle,      // All banks are idle

                    b2x_req,       // Req from bank_ctl

                    b2x_start,     // first chunk of transfer

                    b2x_last,      // last chunk of transfer

                    b2x_id,        // Transfer ID

                    b2x_ba,        // bank address

                    b2x_addr,      // row/col address

                    b2x_len,       // transfer length

                    b2x_cmd,       // transfer command

                    b2x_wrap,      // Wrap mode transfer

                    x2b_ack,       // command accepted

                    /* Status to bank_ctl, req_gen */

                    b2x_tras_ok,   // Tras for all banks expired

                    x2b_refresh,   // We did a refresh

                    x2b_pre_ok,    // OK to do a precharge (per bank)

                    x2b_act_ok,    // OK to do an activate

                    x2b_rdok,      // OK to do a read

                    x2b_wrok,      // OK to do a write

                    /* SDRAM I/O */

                    sdr_cs_n,

                    sdr_cke,

                    sdr_ras_n,

                    sdr_cas_n,

                    sdr_we_n,

                    sdr_dqm,

                    sdr_ba,

                    sdr_addr,

                    sdr_din,

                    sdr_dout,

                    sdr_den_n,

                    /* Data Flow to the app */

                    x2a_rdstart,

                    x2a_wrstart,

                    x2a_rdlast,

                    x2a_wrlast,

                    x2a_id,

                    a2x_wrdt,

                    a2x_wren_n,

                    x2a_wrnext,

                    x2a_rddt,

                    x2a_rdok,

                    sdr_init_done,

                    /* SDRAM Parameters */

                    sdram_enable,

                    sdram_mode_reg,

                    /* output for generate row address of the transfer */

                    xfr_bank_sel,

                    /* SDRAM Timing */

                    cas_latency,

                    trp_delay,     // Precharge to refresh delay

                    trcar_delay,   // Auto-refresh period

                    twr_delay,     // Write recovery delay

                    rfsh_time,     // time per row (31.25 or 15.6125 uS)

                    rfsh_rmax);    // Number of rows to rfsh at a time (<120uS)

parameter  APP_AW   = 30;  // Application Address Width

parameter  APP_DW   = 32;  // Application Data Width 

parameter  APP_BW   = 4;   // Application Byte Width

parameter  SDR_DW   = 16;  // SDR Data Width 

parameter  SDR_BW   = 2;   // SDR Byte Width

// 12 bit subtractor is not feasibile for FPGA, so changed to 8 bits

parameter  REQ_BW   = (`TARGET_DESIGN == `FPGA) ? 8 : 12;   //  Request Width

input            clk, reset_n;

   /* Req from bank_ctl */

input                   b2x_req, b2x_start, b2x_last, b2x_tras_ok,

                                b2x_wrap, r2x_idle, b2x_idle;

input [`SDR_REQ_ID_W-1:0]        b2x_id;

input [1:0]                      b2x_ba;

input [11:0]             b2x_addr;

input [REQ_BW-1:0]       b2x_len;

input [1:0]                      b2x_cmd;

output                  x2b_ack;

/* Status to bank_ctl */

output [3:0]             x2b_pre_ok;

output                  x2b_refresh, x2b_act_ok, x2b_rdok,

                                x2b_wrok;

/* Data Flow to the app */

output                  x2a_rdstart, x2a_wrstart, x2a_rdlast, x2a_wrlast;

output [`SDR_REQ_ID_W-1:0]       x2a_id;

input [SDR_DW-1:0]       a2x_wrdt;

input [SDR_BW-1:0]       a2x_wren_n;

output [SDR_DW-1:0]      x2a_rddt;

output                  x2a_wrnext, x2a_rdok, sdr_init_done;

/* Interface to SDRAMs */

output                  sdr_cs_n, sdr_cke, sdr_ras_n, sdr_cas_n,

                                sdr_we_n;

output [SDR_BW-1:0]      sdr_dqm;

output [1:0]             sdr_ba;

output [11:0]            sdr_addr;

input [SDR_DW-1:0]       sdr_din;

output [SDR_DW-1:0]      sdr_dout;

output [SDR_BW-1:0]      sdr_den_n;

   output [1:0]                  xfr_bank_sel;

   input                        sdram_enable;

   input [11:0]          sdram_mode_reg;

   input [2:0]                   cas_latency;

   input [3:0]                   trp_delay, trcar_delay, twr_delay;

   input [`SDR_RFSH_TIMER_W-1 : 0] rfsh_time;

   input [`SDR_RFSH_ROW_CNT_W-1:0] rfsh_rmax;

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

   // Internal Nets

   `define XFR_IDLE        2'b00

   `define XFR_WRITE       2'b01

   `define XFR_READ        2'b10

   `define XFR_RDWT        2'b11

   reg [1:0]                     xfr_st, next_xfr_st;

   reg [11:0]                    xfr_caddr;

   wire                         last_burst;

   wire                         x2a_rdstart, x2a_wrstart, x2a_rdlast, x2a_wrlast;

   reg                          l_start, l_last, l_wrap;

   wire [`SDR_REQ_ID_W-1:0]      x2a_id;

   reg [`SDR_REQ_ID_W-1:0]       l_id;

   wire [1:0]                    xfr_ba;

   reg [1:0]                     l_ba;

   wire [11:0]                   xfr_addr;

   wire [REQ_BW-1:0]     xfr_len, next_xfr_len;

   reg [REQ_BW-1:0]      l_len;

   reg                          mgmt_idle, mgmt_req;

   reg [3:0]                     mgmt_cmd;

   reg [11:0]                    mgmt_addr;

   reg [1:0]                     mgmt_ba;

   reg                          sel_mgmt, sel_b2x;

   reg                          cb_pre_ok, rdok, wrok, wr_next,

                                rd_next, sdr_init_done, act_cmd, d_act_cmd;

   wire [3:0]                    b2x_sdr_cmd, xfr_cmd;

   reg [3:0]                     i_xfr_cmd;

   wire                         mgmt_ack, x2b_ack, b2x_read, b2x_write,

                                b2x_prechg, d_rd_next, dt_next, xfr_end,

                                rd_pipe_mt, ld_xfr, rd_last, d_rd_last,

                                wr_last, l_xfr_end, rd_start, d_rd_start,

                                wr_start, page_hit, burst_bdry, xfr_wrap,

                                b2x_prechg_hit;

   reg [4:0]                     l_rd_next, l_rd_start, l_rd_last;

   assign b2x_read = (b2x_cmd == `OP_RD) ? 1'b1 : 1'b0;

   assign b2x_write = (b2x_cmd == `OP_WR) ? 1'b1 : 1'b0;

   assign b2x_prechg = (b2x_cmd == `OP_PRE) ? 1'b1 : 1'b0;

   assign b2x_sdr_cmd = (b2x_cmd == `OP_PRE) ? `SDR_PRECHARGE :

                        (b2x_cmd == `OP_ACT) ? `SDR_ACTIVATE :

                        (b2x_cmd == `OP_RD) ? `SDR_READ :

                        (b2x_cmd == `OP_WR) ? `SDR_WRITE : `SDR_DESEL;

   assign page_hit = (b2x_ba == l_ba) ? 1'b1 : 1'b0;

   assign b2x_prechg_hit = b2x_prechg & page_hit;

   assign xfr_cmd = (sel_mgmt) ? mgmt_cmd :

                    (sel_b2x) ? b2x_sdr_cmd : i_xfr_cmd;

   assign xfr_addr = (sel_mgmt) ? mgmt_addr :

                     (sel_b2x) ? b2x_addr : xfr_caddr+1;

   assign mgmt_ack = sel_mgmt;

   assign x2b_ack = sel_b2x;

   assign ld_xfr = sel_b2x & (b2x_read | b2x_write);

   assign xfr_len = (ld_xfr) ? b2x_len : l_len;

   //assign next_xfr_len = (l_xfr_end && !ld_xfr) ? l_len : xfr_len - 1;

   assign next_xfr_len = (ld_xfr) ? b2x_len :

                         (l_xfr_end) ? l_len:  l_len - 1;

   assign d_rd_next = (cas_latency == 2'b01) ? l_rd_next[2] :

                      (cas_latency == 2'b10) ? l_rd_next[3] :

                      l_rd_next[4];

   assign d_rd_last = (cas_latency == 2'b01) ? l_rd_last[2] :

                      (cas_latency == 2'b10) ? l_rd_last[3] :

                      l_rd_last[4];

   assign d_rd_start = (cas_latency == 2'b01) ? l_rd_start[2] :

                      (cas_latency == 2'b10) ? l_rd_start[3] :

                      l_rd_start[4];

   assign rd_pipe_mt = (cas_latency == 2'b01) ? ~|l_rd_next[1:0] :

                       (cas_latency == 2'b10) ? ~|l_rd_next[2:0] :

                       ~|l_rd_next[3:0];

   assign dt_next = wr_next | d_rd_next;

   assign xfr_end = ~|xfr_len;

   assign l_xfr_end = ~|(l_len-1);

   assign rd_start = ld_xfr & b2x_read & b2x_start;

   assign wr_start = ld_xfr & b2x_write & b2x_start;

   assign rd_last = rd_next & last_burst & ~|xfr_len[REQ_BW-1:1];

   //assign wr_last = wr_next & last_burst & ~|xfr_len[APP_RW-1:1];

   assign wr_last = last_burst & ~|xfr_len[REQ_BW-1:1];

   //assign xfr_ba = (ld_xfr) ? b2x_ba : l_ba;

   assign xfr_ba = (sel_mgmt) ? mgmt_ba :

                   (sel_b2x) ? b2x_ba : l_ba;

   assign xfr_wrap = (ld_xfr) ? b2x_wrap : l_wrap;

//   assign burst_bdry = ~|xfr_caddr[2:0];

   wire [1:0] xfr_caddr_lsb = (xfr_caddr[1:0]+1);

   assign burst_bdry = ~|(xfr_caddr_lsb[1:0]);

   always @ (posedge clk) begin

      if (~reset_n) begin

         xfr_caddr <= 12'b0;

         l_start <= 1'b0;

         l_last <= 1'b0;

         l_wrap <= 1'b0;

         l_id <= 0;

         l_ba <= 0;

         l_len <= 0;

         l_rd_next <= 5'b0;

         l_rd_start <= 5'b0;

         l_rd_last <= 5'b0;

         act_cmd <= 1'b0;

         d_act_cmd <= 1'b0;

         xfr_st <= `XFR_IDLE;

      end // if (~reset_n)

      else begin

         xfr_caddr <= (ld_xfr) ? b2x_addr :

                      (rd_next | wr_next) ? xfr_caddr + 1 : xfr_caddr;

         l_start <= (dt_next) ? 1'b0 :

                   (ld_xfr) ? b2x_start : l_start;

         l_last <= (ld_xfr) ? b2x_last : l_last;

         l_wrap <= (ld_xfr) ? b2x_wrap : l_wrap;

         l_id <= (ld_xfr) ? b2x_id : l_id;

         l_ba <= (ld_xfr) ? b2x_ba : l_ba;

         l_len <= next_xfr_len;

         l_rd_next <= {l_rd_next[3:0], rd_next};

         l_rd_start <= {l_rd_start[3:0], rd_start};

         l_rd_last <= {l_rd_last[3:0], rd_last};

         act_cmd <= (xfr_cmd == `SDR_ACTIVATE) ? 1'b1 : 1'b0;

         d_act_cmd <= act_cmd;

         xfr_st <= next_xfr_st;

      end // else: !if(~reset_n)

   end // always @ (posedge clk)

   always @ (*) begin

      case (xfr_st)

        `XFR_IDLE : begin

           sel_mgmt = mgmt_req;

           sel_b2x = ~mgmt_req & sdr_init_done & b2x_req;

           i_xfr_cmd = `SDR_DESEL;

           rd_next = ~mgmt_req & sdr_init_done & b2x_req & b2x_read;

           wr_next = ~mgmt_req & sdr_init_done & b2x_req & b2x_write;

           rdok = ~mgmt_req;

           cb_pre_ok = 1'b1;

           wrok = ~mgmt_req;

           next_xfr_st = (mgmt_req | ~sdr_init_done) ? `XFR_IDLE :

                         (~b2x_req) ? `XFR_IDLE :

                         (b2x_read) ? `XFR_READ :

                         (b2x_write) ? `XFR_WRITE : `XFR_IDLE;

        end // case: `XFR_IDLE

        `XFR_READ : begin

           rd_next = ~l_xfr_end |

                     l_xfr_end & ~mgmt_req & b2x_req & b2x_read;

           wr_next = 1'b0;

           rdok = l_xfr_end & ~mgmt_req;

           // Break the timing path for FPGA Based Design

           cb_pre_ok = (`TARGET_DESIGN == `FPGA) ? 1'b0 : l_xfr_end;

           wrok = 1'b0;

           sel_mgmt = 1'b0;

           if (l_xfr_end) begin           // end of transfer

              if (~l_wrap) begin

                 // Current transfer was not wrap mode, may need BT

                 // If next cmd is a R or W or PRE to same bank allow

                 // it else issue BT 

                 // This is a little pessimistic since BT is issued

                 // for non-wrap mode transfers even if the transfer

                 // ends on a burst boundary, but is felt to be of

                 // minimal performance impact.

                 i_xfr_cmd = `SDR_BT;

                 sel_b2x = b2x_req & ~mgmt_req & (b2x_read | b2x_prechg_hit);

              end // if (~l_wrap)

              else begin

                 // Wrap mode transfer, by definition is end of burst

                 // boundary 

                 i_xfr_cmd = `SDR_DESEL;

                 sel_b2x = b2x_req & ~mgmt_req & ~b2x_write;

              end // else: !if(~l_wrap)

              next_xfr_st = (sdr_init_done) ? ((b2x_req & ~mgmt_req & b2x_read) ? `XFR_READ : `XFR_RDWT) : `XFR_IDLE;

           end // if (l_xfr_end)

           else begin

              // Not end of transfer

              // If current transfer was not wrap mode and we are at

              // the start of a burst boundary issue another R cmd to

              // step sequemtially thru memory, ELSE,

              // issue precharge/activate commands from the bank control

              i_xfr_cmd = (burst_bdry & ~l_wrap) ? `SDR_READ : `SDR_DESEL;

              sel_b2x = ~(burst_bdry & ~l_wrap) & b2x_req;

              next_xfr_st = `XFR_READ;

           end // else: !if(l_xfr_end)

        end // case: `XFR_READ

        `XFR_RDWT : begin

           rd_next = ~mgmt_req & b2x_req & b2x_read;

           wr_next = rd_pipe_mt & ~mgmt_req & b2x_req & b2x_write;

           rdok = ~mgmt_req;

           cb_pre_ok = 1'b1;

           wrok = rd_pipe_mt & ~mgmt_req;

           sel_mgmt = mgmt_req;

           sel_b2x = ~mgmt_req & b2x_req;

           i_xfr_cmd = `SDR_DESEL;

           next_xfr_st = (~mgmt_req & b2x_req & b2x_read) ? `XFR_READ :

                         (~rd_pipe_mt) ? `XFR_RDWT :

                         (~mgmt_req & b2x_req & b2x_write) ? `XFR_WRITE :

                         `XFR_IDLE;

        end // case: `XFR_RDWT

        `XFR_WRITE : begin

           rd_next = l_xfr_end & ~mgmt_req & b2x_req & b2x_read;

           wr_next = ~l_xfr_end |

                     l_xfr_end & ~mgmt_req & b2x_req & b2x_write;

           rdok = l_xfr_end & ~mgmt_req;

           cb_pre_ok = 1'b0;

           wrok = l_xfr_end & ~mgmt_req;

           sel_mgmt = 1'b0;

           if (l_xfr_end) begin           // End of transfer

              if (~l_wrap) begin

                 // Current transfer was not wrap mode, may need BT

                 // If next cmd is a R or W allow it else issue BT 

                 // This is a little pessimistic since BT is issued

                 // for non-wrap mode transfers even if the transfer

                 // ends on a burst boundary, but is felt to be of

                 // minimal performance impact.

                 sel_b2x = b2x_req & ~mgmt_req & (b2x_read | b2x_write);

                 i_xfr_cmd = `SDR_BT;

              end // if (~l_wrap)

              else begin

                 // Wrap mode transfer, by definition is end of burst

                 // boundary 

                 sel_b2x = b2x_req & ~mgmt_req & ~b2x_prechg_hit;

                 i_xfr_cmd = `SDR_DESEL;

              end // else: !if(~l_wrap)

              next_xfr_st = (~mgmt_req & b2x_req & b2x_read) ? `XFR_READ :

                            (~mgmt_req & b2x_req & b2x_write) ? `XFR_WRITE :

                            `XFR_IDLE;

           end // if (l_xfr_end)

           else begin

              // Not end of transfer

              // If current transfer was not wrap mode and we are at

              // the start of a burst boundary issue another R cmd to

              // step sequemtially thru memory, ELSE,

              // issue precharge/activate commands from the bank control

              if (burst_bdry & ~l_wrap) begin

                 sel_b2x = 1'b0;

                 i_xfr_cmd = `SDR_WRITE;

              end // if (burst_bdry & ~l_wrap)

              else begin

                 sel_b2x = b2x_req & ~mgmt_req;

                 i_xfr_cmd = `SDR_DESEL;

              end // else: !if(burst_bdry & ~l_wrap)

              next_xfr_st = `XFR_WRITE;

           end // else: !if(l_xfr_end)

        end // case: `XFR_WRITE

      endcase // case(xfr_st)

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

   // signals to bank_ctl (x2b_refresh, x2b_act_ok, x2b_rdok, x2b_wrok,

   // x2b_pre_ok[3:0] 

   assign x2b_refresh = (xfr_cmd == `SDR_REFRESH) ? 1'b1 : 1'b0;

   assign x2b_act_ok = ~act_cmd & ~d_act_cmd;

   assign x2b_rdok = rdok;

   assign x2b_wrok = wrok;

   //assign x2b_pre_ok[0] = (l_ba == 2'b00) ? cb_pre_ok : 1'b1;

   //assign x2b_pre_ok[1] = (l_ba == 2'b01) ? cb_pre_ok : 1'b1;

   //assign x2b_pre_ok[2] = (l_ba == 2'b10) ? cb_pre_ok : 1'b1;

   //assign x2b_pre_ok[3] = (l_ba == 2'b11) ? cb_pre_ok : 1'b1;

   assign x2b_pre_ok[0] = cb_pre_ok;

   assign x2b_pre_ok[1] = cb_pre_ok;

   assign x2b_pre_ok[2] = cb_pre_ok;

   assign x2b_pre_ok[3] = cb_pre_ok;

   assign last_burst = (ld_xfr) ? b2x_last : l_last;

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

   // APP Data I/F

   wire [SDR_DW-1:0]     x2a_rddt;

   //assign x2a_start = (ld_xfr) ? b2x_start : l_start;

   assign x2a_rdstart = d_rd_start;

   assign x2a_wrstart = wr_start;

   assign x2a_rdlast = d_rd_last;

   assign x2a_wrlast = wr_last;

   assign x2a_id = (ld_xfr) ? b2x_id : l_id;

   assign x2a_rddt = sdr_din;

   assign x2a_wrnext = wr_next;

   assign x2a_rdok = d_rd_next;

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

   // SDRAM I/F

   reg                          sdr_cs_n, sdr_cke, sdr_ras_n, sdr_cas_n,

                                sdr_we_n;

   reg [SDR_BW-1:0]      sdr_dqm;

   reg [1:0]                     sdr_ba;

   reg [11:0]                    sdr_addr;

   reg [SDR_DW-1:0]      sdr_dout;

   reg [SDR_BW-1:0]      sdr_den_n;

   always @ (posedge clk)

      if (~reset_n) begin

         sdr_cs_n <= 1'b1;

         sdr_cke <= 1'b1;

         sdr_ras_n <= 1'b1;

         sdr_cas_n <= 1'b1;

         sdr_we_n <= 1'b1;

         sdr_dqm   <= {SDR_BW{1'b1}};

         sdr_den_n <= {SDR_BW{1'b1}};

      end // if (~reset_n)

      else begin

         sdr_cs_n <= xfr_cmd[3];

         sdr_ras_n <= xfr_cmd[2];

         sdr_cas_n <= xfr_cmd[1];

         sdr_we_n <= xfr_cmd[0];

         sdr_cke <= (xfr_st != `XFR_IDLE) ? 1'b1 :

                    ~(mgmt_idle & b2x_idle & r2x_idle);

         sdr_dqm <= (wr_next) ? a2x_wren_n : {SDR_BW{1'b0}};

         sdr_den_n <= (wr_next) ? {SDR_BW{1'b0}} : {SDR_BW{1'b1}};

      end // else: !if(~reset_n)

   always @ (posedge clk) begin

      if (~xfr_cmd[3]) begin

         sdr_addr <= xfr_addr;

         sdr_ba <= xfr_ba;

      end // if (~xfr_cmd[3])

      sdr_dout <= (wr_next) ? a2x_wrdt : sdr_dout;

   end // always @ (posedge clk)

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

   // Refresh and Initialization

   `define MGM_POWERUP         3'b000

   `define MGM_PRECHARGE    3'b001

   `define MGM_PCHWT        3'b010

   `define MGM_REFRESH      3'b011

   `define MGM_REFWT        3'b100

   `define MGM_MODE_REG     3'b101

   `define MGM_MODE_WT      3'b110

   `define MGM_ACTIVE       3'b111

   reg [2:0]       mgmt_st, next_mgmt_st;

   reg [3:0]        tmr0, tmr0_d;

   reg [3:0]        cntr1, cntr1_d;

   wire            tmr0_tc, cntr1_tc, rfsh_timer_tc, ref_req, precharge_ok;

   reg             ld_tmr0, ld_cntr1, dec_cntr1, set_sdr_init_done;

   reg [`SDR_RFSH_TIMER_W-1 : 0]  rfsh_timer;

   reg [`SDR_RFSH_ROW_CNT_W-1:0]  rfsh_row_cnt;

   always @ (posedge clk)

      if (~reset_n) begin

         mgmt_st <= `MGM_POWERUP;

         tmr0 <= 4'b0;

         cntr1 <= 4'h7;

         rfsh_timer <= 0;

         rfsh_row_cnt <= 0;

         sdr_init_done <= 1'b0;

      end // if (~reset_n)

      else begin

         mgmt_st <= next_mgmt_st;

         tmr0 <= (ld_tmr0) ? tmr0_d :

                  (~tmr0_tc) ? tmr0 - 1 : tmr0;

         cntr1 <= (ld_cntr1) ? cntr1_d :

                  (dec_cntr1) ? cntr1 - 1 : cntr1;

         sdr_init_done <= (set_sdr_init_done | sdr_init_done) & sdram_enable;

         rfsh_timer <= (rfsh_timer_tc) ? 0 : rfsh_timer + 1;

         rfsh_row_cnt <= (~set_sdr_init_done) ? 0 :

                         (rfsh_timer_tc) ? rfsh_row_cnt + 1 : rfsh_row_cnt;

      end // else: !if(~reset_n)

   assign tmr0_tc = ~|tmr0;

   assign cntr1_tc = ~|cntr1;

   assign rfsh_timer_tc = (rfsh_timer == rfsh_time) ? 1'b1 : 1'b0;

   assign ref_req = (rfsh_row_cnt >= rfsh_rmax) ? 1'b1 : 1'b0;

   assign precharge_ok = cb_pre_ok & b2x_tras_ok;

   assign xfr_bank_sel = l_ba;

   always @ (mgmt_st or sdram_enable or mgmt_ack or trp_delay or tmr0_tc or

             cntr1_tc or trcar_delay or rfsh_row_cnt or ref_req or sdr_init_done

             or precharge_ok or sdram_mode_reg) begin

      case (mgmt_st)          // synopsys full_case parallel_case

        `MGM_POWERUP : begin

           mgmt_idle = 1'b0;

           mgmt_req = 1'b0;

           mgmt_cmd = `SDR_DESEL;

           mgmt_ba = 2'b0;

           mgmt_addr = 12'h400;    // A10 = 1 => all banks

           ld_tmr0 = 1'b0;

           tmr0_d = 4'b0;

           dec_cntr1 = 1'b0;

           ld_cntr1 = 1'b1;

           cntr1_d = 4'hf; // changed for sdrams with higher refresh cycles during initialization

           set_sdr_init_done = 1'b0;

           next_mgmt_st = (sdram_enable) ? `MGM_PRECHARGE : `MGM_POWERUP;

        end // case: `MGM_POWERUP