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[/] [openrisc/] [trunk/] [or1200/] [rtl/] [verilog/] [or1200_if.v] - Blame information for rev 358

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//////////////////////////////////////////////////////////////////////
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////                                                              ////
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////  OR1200's instruction fetch                                  ////
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////                                                              ////
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////  This file is part of the OpenRISC 1200 project              ////
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////  http://www.opencores.org/project,or1k                       ////
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////                                                              ////
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////  Description                                                 ////
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////  PC, instruction fetch, interface to IC.                     ////
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////                                                              ////
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////  To Do:                                                      ////
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////   - make it smaller and faster                               ////
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////                                                              ////
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////  Author(s):                                                  ////
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////      - Damjan Lampret, lampret@opencores.org                 ////
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////                                                              ////
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//////////////////////////////////////////////////////////////////////
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////                                                              ////
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//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////
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////                                                              ////
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//// This source file may be used and distributed without         ////
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//// restriction provided that this copyright statement is not    ////
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//// removed from the file and that any derivative work contains  ////
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//// the original copyright notice and the associated disclaimer. ////
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////                                                              ////
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//// This source file is free software; you can redistribute it   ////
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//// and/or modify it under the terms of the GNU Lesser General   ////
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//// Public License as published by the Free Software Foundation; ////
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//// either version 2.1 of the License, or (at your option) any   ////
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//// later version.                                               ////
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////                                                              ////
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//// This source is distributed in the hope that it will be       ////
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//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////
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//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////
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//// PURPOSE.  See the GNU Lesser General Public License for more ////
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//// details.                                                     ////
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////                                                              ////
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//// You should have received a copy of the GNU Lesser General    ////
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//// Public License along with this source; if not, download it   ////
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//// from http://www.opencores.org/lgpl.shtml                     ////
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////                                                              ////
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//////////////////////////////////////////////////////////////////////
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//
44 141 marcus.erl
// $Log: or1200_if.v,v $
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// Revision 2.0  2010/06/30 11:00:00  ORSoC
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// Major update: 
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// Structure reordered and bugs fixed. 
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// synopsys translate_off
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`include "timescale.v"
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// synopsys translate_on
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`include "or1200_defines.v"
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module or1200_if(
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        // Clock and reset
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        clk, rst,
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        // External i/f to IC
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        icpu_dat_i, icpu_ack_i, icpu_err_i, icpu_adr_i, icpu_tag_i,
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        // Internal i/f
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        if_freeze, if_insn, if_pc, if_flushpipe, saving_if_insn,
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        if_stall, no_more_dslot, genpc_refetch, rfe,
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        except_itlbmiss, except_immufault, except_ibuserr
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);
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//
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// I/O
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//
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//
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// Clock and reset
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//
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input                           clk;
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input                           rst;
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//
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// External i/f to IC
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//
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input   [31:0]                   icpu_dat_i;
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input                           icpu_ack_i;
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input                           icpu_err_i;
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input   [31:0]                   icpu_adr_i;
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input   [3:0]                    icpu_tag_i;
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//
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// Internal i/f
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//
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input                           if_freeze;
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output  [31:0]                   if_insn;
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output  [31:0]                   if_pc;
92 141 marcus.erl
input                           if_flushpipe;
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output                          saving_if_insn;
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output                          if_stall;
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input                           no_more_dslot;
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output                          genpc_refetch;
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input                           rfe;
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output                          except_itlbmiss;
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output                          except_immufault;
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output                          except_ibuserr;
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//
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// Internal wires and regs
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//
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wire                    save_insn;
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wire                    if_bypass;
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reg                     if_bypass_reg;
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reg     [31:0]           insn_saved;
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reg     [31:0]           addr_saved;
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reg     [2:0]            err_saved;
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reg                     saved;
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113 141 marcus.erl
assign save_insn = (icpu_ack_i | icpu_err_i) & if_freeze & !saved;
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assign saving_if_insn = !if_flushpipe & save_insn;
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//
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// IF bypass 
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//
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assign if_bypass = icpu_adr_i[0] ? 1'b0 : if_bypass_reg | if_flushpipe;
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always @(posedge clk or `OR1200_RST_EVENT rst)
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        if (rst == `OR1200_RST_VALUE)
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                if_bypass_reg <=  1'b0;
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        else
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                if_bypass_reg <=  if_bypass;
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//
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// IF stage insn
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//
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assign if_insn = no_more_dslot | rfe | if_bypass ? {`OR1200_OR32_NOP, 26'h041_0000} : saved ? insn_saved : icpu_ack_i ? icpu_dat_i : {`OR1200_OR32_NOP, 26'h061_0000};
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assign if_pc = saved ? addr_saved : {icpu_adr_i[31:2], 2'h0};
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assign if_stall = !icpu_err_i & !icpu_ack_i & !saved;
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assign genpc_refetch = saved & icpu_ack_i;
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assign except_itlbmiss = no_more_dslot ? 1'b0 : saved ? err_saved[0] : icpu_err_i & (icpu_tag_i == `OR1200_ITAG_TE);
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assign except_immufault = no_more_dslot ? 1'b0 : saved ? err_saved[1] : icpu_err_i & (icpu_tag_i == `OR1200_ITAG_PE);
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assign except_ibuserr = no_more_dslot ? 1'b0 : saved ? err_saved[2] : icpu_err_i & (icpu_tag_i == `OR1200_ITAG_BE);
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//
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// Flag for saved insn/address
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//
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always @(posedge clk or `OR1200_RST_EVENT rst)
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        if (rst == `OR1200_RST_VALUE)
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                saved <=  1'b0;
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        else if (if_flushpipe)
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                saved <=  1'b0;
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        else if (save_insn)
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                saved <=  1'b1;
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        else if (!if_freeze)
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                saved <=  1'b0;
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//
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// Store fetched instruction
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//
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always @(posedge clk or `OR1200_RST_EVENT rst)
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        if (rst == `OR1200_RST_VALUE)
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                insn_saved <=  {`OR1200_OR32_NOP, 26'h041_0000};
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        else if (if_flushpipe)
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                insn_saved <=  {`OR1200_OR32_NOP, 26'h041_0000};
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        else if (save_insn)
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                insn_saved <=  icpu_err_i ? {`OR1200_OR32_NOP, 26'h041_0000} : icpu_dat_i;
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        else if (!if_freeze)
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                insn_saved <=  {`OR1200_OR32_NOP, 26'h041_0000};
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//
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// Store fetched instruction's address
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//
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always @(posedge clk or `OR1200_RST_EVENT rst)
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        if (rst == `OR1200_RST_VALUE)
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                addr_saved <=  32'h00000000;
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        else if (if_flushpipe)
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                addr_saved <=  32'h00000000;
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        else if (save_insn)
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                addr_saved <=  {icpu_adr_i[31:2], 2'b00};
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        else if (!if_freeze)
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                addr_saved <=  {icpu_adr_i[31:2], 2'b00};
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177 141 marcus.erl
//
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// Store fetched instruction's error tags 
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//
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always @(posedge clk or `OR1200_RST_EVENT rst)
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        if (rst == `OR1200_RST_VALUE)
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                err_saved <=  3'b000;
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        else if (if_flushpipe)
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                err_saved <=  3'b000;
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        else if (save_insn) begin
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                err_saved[0] <=  icpu_err_i & (icpu_tag_i == `OR1200_ITAG_TE);
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                err_saved[1] <=  icpu_err_i & (icpu_tag_i == `OR1200_ITAG_PE);
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                err_saved[2] <=  icpu_err_i & (icpu_tag_i == `OR1200_ITAG_BE);
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        end
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        else if (!if_freeze)
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                err_saved <=  3'b000;
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endmodule

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