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

////                                                              ////

////  OR1200's IC FSM                                             ////

////                                                              ////

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

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

////                                                              ////

////  Description                                                 ////

////  Insn cache state machine                                    ////

////                                                              ////

////  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_ic_fsm.v,v $

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

// Minor update: 

// Bugs fixed. 

//

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

`include "or1200_defines.v"

`define OR1200_ICFSM_IDLE       2'd0

`define OR1200_ICFSM_CFETCH     2'd1

`define OR1200_ICFSM_LREFILL3   2'd2

`define OR1200_ICFSM_IFETCH     2'd3

//

// Instruction cache FSM

//

module or1200_ic_fsm(

        // Clock and reset

        clk, rst,

        // Internal i/f to top level IC

        ic_en, icqmem_cycstb_i, icqmem_ci_i,

        tagcomp_miss,

        biudata_valid, biudata_error,

        start_addr, saved_addr,

        icram_we, tag_we,

        biu_read,

        first_hit_ack, first_miss_ack, first_miss_err,

        burst

);

//

// I/O

//

input                           clk;

input                           rst;

input                           ic_en;

input                           icqmem_cycstb_i;

input                           icqmem_ci_i;

input                           tagcomp_miss;

input                           biudata_valid;

input                           biudata_error;

input   [31:0]                   start_addr;

output  [31:0]                   saved_addr;

output  [3:0]                    icram_we;

output                          biu_read;

output                          first_hit_ack;

output                          first_miss_ack;

output                          first_miss_err;

output                          burst;

output                          tag_we;

//

// Internal wires and regs

//

reg     [31:0]                   saved_addr_r;

reg     [1:0]                    state;

reg [`OR1200_ICLS-1:0]           cnt;

reg                             hitmiss_eval;

reg                             load;

reg                             cache_inhibit;

reg                             last_eval_miss; // JPB

   //

   // Generate of ICRAM write enables

   //

   assign icram_we = {4{biu_read & biudata_valid & !cache_inhibit}};

   assign tag_we = biu_read & biudata_valid & !cache_inhibit;

   //

   // BIU read and write

   //

   assign biu_read = (hitmiss_eval & tagcomp_miss) | (!hitmiss_eval & load);

   //assign saved_addr = hitmiss_eval ? start_addr : saved_addr_r;

   assign saved_addr = saved_addr_r;

   // Asserted when a cache hit occurs and the first word is ready/valid

   assign first_hit_ack = (state == `OR1200_ICFSM_CFETCH) & hitmiss_eval &

                          !tagcomp_miss & !cache_inhibit;

   // Asserted when a cache miss occurs, but the first word of the new

   // cache line is ready (on the bus)

   // Cache hits overpower bus data

   assign first_miss_ack = (state == `OR1200_ICFSM_CFETCH) & biudata_valid &

                           ~first_hit_ack;

   // Asserted when a cache occurs, but there was a bus error with handling

   // the old line or fetching the new line

   assign first_miss_err = (state == `OR1200_ICFSM_CFETCH) & biudata_error;

   //

   // Assert burst when doing reload of complete cache line

   //

   assign burst = (state == `OR1200_ICFSM_CFETCH) & tagcomp_miss &

                  !cache_inhibit | (state == `OR1200_ICFSM_LREFILL3);

   //

   // Main IC FSM

   //

   always @(posedge clk or `OR1200_RST_EVENT rst) begin

      if (rst == `OR1200_RST_VALUE) begin

         state <=  `OR1200_ICFSM_IDLE;

         saved_addr_r <=  32'b0;

         hitmiss_eval <=  1'b0;

         load <=  1'b0;

         cnt <=  `OR1200_ICLS'd0;

         cache_inhibit <=  1'b0;

         last_eval_miss <= 0; // JPB

      end

      else

        case (state)    // synopsys parallel_case

          `OR1200_ICFSM_IDLE :

            if (ic_en & icqmem_cycstb_i) begin          // fetch

               state <=  `OR1200_ICFSM_CFETCH;

               saved_addr_r <=  start_addr;

               hitmiss_eval <=  1'b1;

               load <=  1'b1;

               cache_inhibit <=  icqmem_ci_i;

               last_eval_miss <= 0; // JPB

            end

            else begin                  // idle

               hitmiss_eval <=  1'b0;

               load <=  1'b0;

               cache_inhibit <=  1'b0;

            end

          `OR1200_ICFSM_CFETCH: begin   // fetch

             if (icqmem_cycstb_i & icqmem_ci_i)

               cache_inhibit <=  1'b1;

             if (hitmiss_eval)

               saved_addr_r[31:`OR1200_ICTAGL] <= start_addr[31:`OR1200_ICTAGL];

             // Check for stopped cache loads

                 // instruction cache turned-off

             if ((!ic_en) ||

                 // fetch aborted (usually caused by IMMU)

                 (hitmiss_eval & !icqmem_cycstb_i) ||

                 (biudata_error) ||  // fetch terminated with an error

                 // fetch from cache-inhibited page

                 (cache_inhibit & biudata_valid)) begin

                state <=  `OR1200_ICFSM_IDLE;

                hitmiss_eval <=  1'b0;

                load <=  1'b0;

                cache_inhibit <=  1'b0;

             end // if ((!ic_en) ||...       

             // fetch missed, wait for first fetch and continue filling line

             else if (tagcomp_miss & biudata_valid) begin

                state <=  `OR1200_ICFSM_LREFILL3;

                saved_addr_r[`OR1200_ICLS-1:2]

                  <= saved_addr_r[`OR1200_ICLS-1:2] + 1;

                hitmiss_eval <=  1'b0;

                cnt <= ((1 << `OR1200_ICLS) - (2 * 4));

                cache_inhibit <=  1'b0;

             end

             // fetch aborted (usually caused by exception)

             else if (!icqmem_cycstb_i

                      & !last_eval_miss // JPB

                      ) begin

                state <=  `OR1200_ICFSM_IDLE;

                hitmiss_eval <=  1'b0;

                load <=  1'b0;

                cache_inhibit <=  1'b0;

             end

             // fetch hit, wait in this state for now

             else if (!tagcomp_miss & !icqmem_ci_i) begin

                saved_addr_r <=  start_addr;

                cache_inhibit <=  1'b0;

             end

             else   // fetch in-progress

               hitmiss_eval <=  1'b0;

             if (hitmiss_eval & !tagcomp_miss) // JPB

               last_eval_miss <= 1; // JPB

          end

          `OR1200_ICFSM_LREFILL3 : begin

             // abort because IC has just been turned off

             if (!ic_en) begin

                // invalidate before IC can be turned on

                state <=  `OR1200_ICFSM_IDLE;

                saved_addr_r <=  start_addr;

                hitmiss_eval <=  1'b0;

                load <=  1'b0;

             end

             // refill ack, more fetchs to come

             else if (biudata_valid && (|cnt)) begin

                cnt <=  cnt - `OR1200_ICLS'd4;

                saved_addr_r[`OR1200_ICLS-1:2]

                  <= saved_addr_r[`OR1200_ICLS-1:2] + 1;

             end

             // last fetch of line refill

             else if (biudata_valid) begin

                state <=  `OR1200_ICFSM_IDLE;

                saved_addr_r <=  start_addr;

                hitmiss_eval <=  1'b0;

                load <=  1'b0;

             end

          end

          default:

            state <=  `OR1200_ICFSM_IDLE;

        endcase

   end

endmodule