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

////                                                              ////

////  OR1200's Data Cache top level                               ////

////                                                              ////

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

////  http://www.opencores.org/cores/or1k/                        ////

////                                                              ////

////  Description                                                 ////

////  Instantiation of all DC blocks.                             ////

////                                                              ////

////  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                     ////

////                                                              ////

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

//

// CVS Revision History

//

// $Log: not supported by cvs2svn $

// Revision 1.9  2001/10/14 13:12:09  lampret

// MP3 version.

//

// Revision 1.1.1.1  2001/10/06 10:18:35  igorm

// no message

//

// Revision 1.4  2001/08/13 03:36:20  lampret

// Added cfg regs. Moved all defines into one defines.v file. More cleanup.

//

// Revision 1.3  2001/08/09 13:39:33  lampret

// Major clean-up.

//

// Revision 1.2  2001/07/22 03:31:53  lampret

// Fixed RAM's oen bug. Cache bypass under development.

//

// Revision 1.1  2001/07/20 00:46:03  lampret

// Development version of RTL. Libraries are missing.

//

//

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

`include "defines.v"

//

// Data cache

//

module dc(

        // Rst, clk and clock control

        clk, rst, clkdiv_by_2,

        // External i/f

        dcbiu_rdy, dcbiu_datain, dcbiu_dataout, dcbiu_addr, dcbiu_read, dcbiu_write, dcbiu_sel,

        // Internal i/f

        dc_en, dclsu_addr, dclsu_lsuop, dclsu_datain, dclsu_dataout, dclsu_stall, dclsu_unstall,

        // SPRs

        spr_cs, spr_write, spr_dat_i

);

parameter dw = `OPERAND_WIDTH;

//

// I/O

//

//

// Clock and reset

//

input                           clk;

input                           rst;

input                           clkdiv_by_2;

//

// External I/F

//

input                           dcbiu_rdy;

input   [dw-1:0]         dcbiu_datain;

output  [31:0]                   dcbiu_addr;

output                          dcbiu_read;

output                          dcbiu_write;

output  [3:0]                    dcbiu_sel;

//

// Internal I/F

//

input                           dc_en;

input   [31:0]                   dclsu_addr;

input   [`LSUOP_WIDTH-1:0]       dclsu_lsuop;

input   [dw-1:0]         dclsu_datain;

output  [dw-1:0]         dclsu_dataout;

output  [dw-1:0]         dcbiu_dataout;

output                          dclsu_stall;

output                          dclsu_unstall;

//

// SPR access

//

input                           spr_cs;

input                           spr_write;

input   [31:0]                   spr_dat_i;

//

// Internal wires and regs

//

wire                            tag_v;

wire    [18:0]                   tag;

wire    [dw-1:0]         to_dcram;

wire    [dw-1:0]         from_dcram;

wire    [dw-1:0]         to_mem2reg;

wire    [31:0]                   saved_addr;

wire                            refill;

wire    [3:0]                    dcram_we;

wire                            dctag_we;

wire    [dw-1:0]         lsu_datain_memaligned;

wire    [31:0]                   dc_addr;

wire                            refill_first;

wire                            refill_prepare;

wire                            refill_start;

wire                            refill_rest;

wire    [`LSUOP_WIDTH-1:0]       dcfsm_lsuop;

wire                            dcfsm_read;

wire                            dcfsm_write;

wire    [1:0]                    mem2reg_addr;

reg                             hit;

reg     [1:0]                    valid_div;

reg     [3:0]                    dcbiu_sel;

reg     [1:0]                    bypass_wait;

wire                            queue;

wire                            cntrbusy;

wire                            dcbiu_valid;

wire    [12:4]                  dctag_addr;

wire                            dctag_en;

wire                            dctag_v;

wire                            dc_inv;

//

// Simple assignments

//

assign dcbiu_addr = dc_addr;

assign dclsu_unstall = dcbiu_rdy;

assign dc_inv = spr_cs & spr_write;

assign dctag_we = refill | dc_inv;

assign dctag_addr = dc_inv ? spr_dat_i[12:4] : dc_addr[12:4];

assign dctag_en = dc_inv | dc_en;

assign dctag_v = ~dc_inv;

//

// Data to BIU is from DCRAM when DC is enabled or from LSU when

// DC is disabled

//

assign dcbiu_dataout = (dc_en) ? from_dcram : lsu_datain_memaligned;

//

// Bypases of the DC when DC is disabled

//

assign dcfsm_lsuop = (dc_en) ? dclsu_lsuop : `LSUOP_NOP;

assign dcbiu_read = (dc_en) ? dcfsm_read : ((|dclsu_lsuop) && ~dclsu_lsuop[3]);

assign dcbiu_write = (dc_en) ? dcfsm_write : ((|dclsu_lsuop) && dclsu_lsuop[3]);

always @(dc_en or dclsu_lsuop or dclsu_addr)

        casex({dc_en, dclsu_lsuop, dclsu_addr[1:0]})

                {1'b0, `LSUOP_SB, 2'b00} : dcbiu_sel = 4'b1000;

                {1'b0, `LSUOP_SB, 2'b01} : dcbiu_sel = 4'b0100;

                {1'b0, `LSUOP_SB, 2'b10} : dcbiu_sel = 4'b0010;

                {1'b0, `LSUOP_SB, 2'b11} : dcbiu_sel = 4'b0001;

                {1'b0, `LSUOP_SH, 2'b00} : dcbiu_sel = 4'b1100;

                {1'b0, `LSUOP_SH, 2'b10} : dcbiu_sel = 4'b0011;

                {1'b0, `LSUOP_SW, 2'b00} : dcbiu_sel = 4'b1111;

                {1'b0, `LSUOP_LBZ, 2'b00}, {1'b0, `LSUOP_LBS, 2'b00} : dcbiu_sel = 4'b1000;

                {1'b0, `LSUOP_LBZ, 2'b01}, {1'b0, `LSUOP_LBS, 2'b01} : dcbiu_sel = 4'b0100;

                {1'b0, `LSUOP_LBZ, 2'b10}, {1'b0, `LSUOP_LBS, 2'b10} : dcbiu_sel = 4'b0010;

                {1'b0, `LSUOP_LBZ, 2'b11}, {1'b0, `LSUOP_LBS, 2'b11} : dcbiu_sel = 4'b0001;

                {1'b0, `LSUOP_LHZ, 2'b00}, {1'b0, `LSUOP_LHS, 2'b00} : dcbiu_sel = 4'b1100;

                {1'b0, `LSUOP_LHZ, 2'b10}, {1'b0, `LSUOP_LHS, 2'b10} : dcbiu_sel = 4'b0011;

                {1'b0, `LSUOP_LWZ, 2'b00}, {1'b0, `LSUOP_LWS, 2'b00} : dcbiu_sel = 4'b1111;

                7'b1xxxxxx : dcbiu_sel = 4'b1111;

                default : dcbiu_sel = 4'b0000;

        endcase

assign mem2reg_addr = (dc_en) ? saved_addr[1:0] : dclsu_addr[1:0];

//

// Wait for DC bypass access

//

always @(posedge rst or posedge clk)

        if (rst)

                bypass_wait <= #1 2'b00;

        else if (dcbiu_valid)

                bypass_wait <= #1 2'b00;

        else if (dcbiu_read | dcbiu_write)

                bypass_wait <= #1 {bypass_wait[0], 1'b1};

        else

                bypass_wait <= #1 2'b00;

//

// Queue

//

assign queue = (refill && (|dcfsm_lsuop) && !refill_first && !refill_rest) ? 1'b1 : 1'b0;

//

// DC/LSU stall

//

//assign dclsu_stall = refill_start | (refill_first & ~dcbiu_valid)| refill_rest | queue | cntrbusy | (~dc_en & bypass_wait[1] & ~dcbiu_valid);

assign dclsu_stall = refill_start | (refill_first & ~dcbiu_valid)| refill_rest | queue | cntrbusy | (~dc_en & (dcbiu_read | dcbiu_write) & ~dcbiu_rdy);

//

// Select between claddr generated by DC FSM and addr[3:2] generated by LSU

//

assign dc_addr = (refill == 1'b1) ? saved_addr : dclsu_addr;

//

// Select between input data generated by LSU or by BIU

//

assign to_dcram = (refill == 1'b1) ? dcbiu_datain : lsu_datain_memaligned;

//

// Select between data generated by DCRAM or passed by BIU

//

assign to_mem2reg = (refill_first == 1'b1) | (~dc_en) ? dcbiu_datain : from_dcram;

//

// Tag comparison

//

always @(tag or saved_addr or tag_v) begin

        if ((tag == saved_addr[31:13]) && tag_v)

                hit = 1'b1;

        else

                hit = 1'b0;

end

//

// Valid_div counts RISC clock cycles by modulo 4

//

always @(posedge clk or posedge rst)

        if (rst)

                valid_div <= #1 2'b0;

        else

                valid_div <= #1 valid_div + 'd1;

//

// dcbiu_valid is one RISC clock cycle long dcbiu_rdy.

// dcbiu_rdy is two or four RISC clock cycles long because memory

// controller works at 1/2 or 1/4 of RISC clock freq (at 1/2 if

// clkdiv_by_2 is asserted).

//

assign dcbiu_valid = dcbiu_rdy & (valid_div[1] | clkdiv_by_2) & valid_div[0];

//

// Generate refill_start that signals to frz_logic a cache linefill is about to begin

//

assign refill_start = (refill_prepare & ~hit) ? 1'b1 : 1'b0;

//

// Instantiation of DC Finite State Machine

//

dc_fsm dc_fsm(

        .clk(clk),

        .rst(rst),

        .lsu_op(dcfsm_lsuop),

        .miss(~hit),

        .biudata_valid(dcbiu_valid),

        .start_addr(dclsu_addr),

        .saved_addr(saved_addr),

        .refill(refill),

        .refill_first(refill_first),

        .refill_prepare(refill_prepare),

        .dcram_we(dcram_we),

        .biu_read(dcfsm_read),

        .biu_write(dcfsm_write),

        .refill_rest(refill_rest),

        .cntrbusy(cntrbusy)

);

//

// Instantiation of Regfile-to-memory aligner

//

reg2mem reg2mem(

        .addr(dc_addr[1:0]),

        .lsu_op(dclsu_lsuop),

        .regdata(dclsu_datain),

        .memdata(lsu_datain_memaligned)

);

//

// Instantiation of DC main memory

//

dc_ram dc_ram(

        .clk(clk),

        .rst(rst),

        .addr(dc_addr[12:2]),

        .en(dc_en),

        .we(dcram_we),

        .datain(to_dcram),

        .dataout(from_dcram)

);

//

// Instantiation of DC TAG memory

//

dc_tag dc_tag(

        .clk(clk),

        .rst(rst),

        .addr(dctag_addr),

        .en(dctag_en),

        .we(dctag_we),

        .datain({dc_addr[31:13], dctag_v}),

        .tag_v(tag_v),

        .tag(tag)

);

//

// Instatiation of Memory-to-regfile aligner

//

mem2reg mem2reg(

        .addr(mem2reg_addr[1:0]),

        .lsu_op(dclsu_lsuop),

        .memdata(to_mem2reg),

        .regdata(dclsu_dataout)

);

endmodule