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//////////////////////////////////////////////////////////////////////

////                                                              ////

////  OR1200's Load/Store unit                                    ////

////                                                              ////

////  This file is part of the OpenRISC 1200 project              ////

////  http://opencores.org/project,or1k                           ////

////                                                              ////

////  Description                                                 ////

////  Interface between CPU and DC.                               ////

////                                                              ////

////  To Do:                                                      ////

////   - make it smaller and faster                               ////

////                                                              ////

////  Author(s):                                                  ////

////      - Damjan Lampret, lampret@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                     ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

//

//

// $Log: or1200_lsu.v,v $

// Revision 2.0  2010/06/30 11:00:00  ORSoC

// Major update: 

// Structure reordered and bugs fixed. 

//

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

`include "or1200_defines.v"

module or1200_lsu(

        // Clock and Reset

        clk, rst,

        // Internal i/f

        id_addrbase, ex_addrbase, id_addrofs, ex_addrofs, id_lsu_op,

        lsu_datain, lsu_dataout, lsu_stall, lsu_unstall,

        du_stall, except_align, except_dtlbmiss, except_dmmufault, except_dbuserr,

        id_freeze, ex_freeze, flushpipe,

        // External i/f to DC

        dcpu_adr_o, dcpu_cycstb_o, dcpu_we_o, dcpu_sel_o, dcpu_tag_o, dcpu_dat_o,

        dcpu_dat_i, dcpu_ack_i, dcpu_rty_i, dcpu_err_i, dcpu_tag_i

);

parameter dw = `OR1200_OPERAND_WIDTH;

parameter aw = `OR1200_REGFILE_ADDR_WIDTH;

//

// I/O

//

//

// Clock and reset

//

input                           clk;

input                           rst;

//

// Internal i/f

//

input   [31:0]                   id_addrbase;

input   [31:0]                   ex_addrbase;

input   [31:0]                   id_addrofs;

input   [31:0]                   ex_addrofs;

input   [`OR1200_LSUOP_WIDTH-1:0] id_lsu_op;

input   [dw-1:0]         lsu_datain;

output  [dw-1:0]         lsu_dataout;

output                          lsu_stall;

output                          lsu_unstall;

input                           du_stall;

output                          except_align;

output                          except_dtlbmiss;

output                          except_dmmufault;

output                          except_dbuserr;

input                           id_freeze;

input                           ex_freeze;

input                           flushpipe;

//

// External i/f to DC

//

output  [31:0]                   dcpu_adr_o;

output                          dcpu_cycstb_o;

output                          dcpu_we_o;

output  [3:0]                    dcpu_sel_o;

output  [3:0]                    dcpu_tag_o;

output  [31:0]                   dcpu_dat_o;

input   [31:0]                   dcpu_dat_i;

input                           dcpu_ack_i;

input                           dcpu_rty_i;

input                           dcpu_err_i;

input   [3:0]                    dcpu_tag_i;

//

// Internal wires/regs

//

reg     [3:0]                    dcpu_sel_o;

reg     [`OR1200_LSUOP_WIDTH-1:0] ex_lsu_op;

wire    [`OR1200_LSUEA_PRECALC:0] id_precalc_sum;

reg     [`OR1200_LSUEA_PRECALC:0] dcpu_adr_r;

reg                             except_align;

//

// ex_lsu_op

//

always @(posedge clk or `OR1200_RST_EVENT rst) begin

    if (rst == `OR1200_RST_VALUE)

        ex_lsu_op <=  `OR1200_LSUOP_NOP;

    else if (!ex_freeze & id_freeze | flushpipe)

        ex_lsu_op <=  `OR1200_LSUOP_NOP;

    else if (!ex_freeze)

        ex_lsu_op <=  id_lsu_op;

end

//

// Precalculate part of load/store EA in ID stage

//

assign id_precalc_sum = id_addrbase[`OR1200_LSUEA_PRECALC-1:0] +

                        id_addrofs[`OR1200_LSUEA_PRECALC-1:0];

always @(posedge clk or `OR1200_RST_EVENT rst) begin

    if (rst == `OR1200_RST_VALUE)

        dcpu_adr_r <=  {`OR1200_LSUEA_PRECALC+1{1'b0}};

    else if (!ex_freeze)

        dcpu_adr_r <=  id_precalc_sum;

end

//

// Generate except_align in ID stage

//

always @(posedge clk or `OR1200_RST_EVENT rst) begin

    if (rst == `OR1200_RST_VALUE)

        except_align <=  1'b0;

    else if (!ex_freeze & id_freeze | flushpipe)

        except_align <=  1'b0;

    else if (!ex_freeze)

        except_align <=  ((id_lsu_op == `OR1200_LSUOP_SH) |

                            (id_lsu_op == `OR1200_LSUOP_LHZ) |

                            (id_lsu_op == `OR1200_LSUOP_LHS)) & id_precalc_sum[0]

                        |  ((id_lsu_op == `OR1200_LSUOP_SW) |

                            (id_lsu_op == `OR1200_LSUOP_LWZ) |

                            (id_lsu_op == `OR1200_LSUOP_LWS)) & |id_precalc_sum[1:0];

end

//

// Internal I/F assignments

//

assign lsu_stall = dcpu_rty_i & dcpu_cycstb_o;

assign lsu_unstall = dcpu_ack_i;

assign except_dtlbmiss = dcpu_err_i & (dcpu_tag_i == `OR1200_DTAG_TE);

assign except_dmmufault = dcpu_err_i & (dcpu_tag_i == `OR1200_DTAG_PE);

assign except_dbuserr = dcpu_err_i & (dcpu_tag_i == `OR1200_DTAG_BE);

//

// External I/F assignments

//

assign dcpu_adr_o[31:`OR1200_LSUEA_PRECALC] =

                                   ex_addrbase[31:`OR1200_LSUEA_PRECALC] +

                                   (ex_addrofs[31:`OR1200_LSUEA_PRECALC] +

                                    // carry from precalc, pad to 30-bits

                                   {{(32-`OR1200_LSUEA_PRECALC)-1{1'b0}},

                                    dcpu_adr_r[`OR1200_LSUEA_PRECALC]});

assign dcpu_adr_o[`OR1200_LSUEA_PRECALC-1:0] = dcpu_adr_r[`OR1200_LSUEA_PRECALC-1:0];

assign dcpu_cycstb_o = du_stall | lsu_unstall | except_align ?

                       1'b0 : |ex_lsu_op;

assign dcpu_we_o = ex_lsu_op[3];

assign dcpu_tag_o = dcpu_cycstb_o ? `OR1200_DTAG_ND : `OR1200_DTAG_IDLE;

always @(ex_lsu_op or dcpu_adr_o)

        casez({ex_lsu_op, dcpu_adr_o[1:0]})

                {`OR1200_LSUOP_SB, 2'b00} : dcpu_sel_o = 4'b1000;

                {`OR1200_LSUOP_SB, 2'b01} : dcpu_sel_o = 4'b0100;

                {`OR1200_LSUOP_SB, 2'b10} : dcpu_sel_o = 4'b0010;

                {`OR1200_LSUOP_SB, 2'b11} : dcpu_sel_o = 4'b0001;

                {`OR1200_LSUOP_SH, 2'b00} : dcpu_sel_o = 4'b1100;

                {`OR1200_LSUOP_SH, 2'b10} : dcpu_sel_o = 4'b0011;

                {`OR1200_LSUOP_SW, 2'b00} : dcpu_sel_o = 4'b1111;

                {`OR1200_LSUOP_LBZ, 2'b00}, {`OR1200_LSUOP_LBS, 2'b00} : dcpu_sel_o = 4'b1000;

                {`OR1200_LSUOP_LBZ, 2'b01}, {`OR1200_LSUOP_LBS, 2'b01} : dcpu_sel_o = 4'b0100;

                {`OR1200_LSUOP_LBZ, 2'b10}, {`OR1200_LSUOP_LBS, 2'b10} : dcpu_sel_o = 4'b0010;

                {`OR1200_LSUOP_LBZ, 2'b11}, {`OR1200_LSUOP_LBS, 2'b11} : dcpu_sel_o = 4'b0001;

                {`OR1200_LSUOP_LHZ, 2'b00}, {`OR1200_LSUOP_LHS, 2'b00} : dcpu_sel_o = 4'b1100;

                {`OR1200_LSUOP_LHZ, 2'b10}, {`OR1200_LSUOP_LHS, 2'b10} : dcpu_sel_o = 4'b0011;

                {`OR1200_LSUOP_LWZ, 2'b00}, {`OR1200_LSUOP_LWS, 2'b00} : dcpu_sel_o = 4'b1111;

                default : dcpu_sel_o = 4'b0000;

        endcase

//

// Instantiation of Memory-to-regfile aligner

//

or1200_mem2reg or1200_mem2reg(

        .addr(dcpu_adr_o[1:0]),

        .lsu_op(ex_lsu_op),

        .memdata(dcpu_dat_i),

        .regdata(lsu_dataout)

);

//

// Instantiation of Regfile-to-memory aligner

//

or1200_reg2mem or1200_reg2mem(

        .addr(dcpu_adr_o[1:0]),

        .lsu_op(ex_lsu_op),

        .regdata(lsu_datain),

        .memdata(dcpu_dat_o)

);

endmodule