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[/] [zipcpu/] [trunk/] [rtl/] [core/] [prefetch.v] - Diff between revs 69 and 201

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Rev 69 Rev 201
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// Creator:     Dan Gisselquist, Ph.D.
// Creator:     Dan Gisselquist, Ph.D.
//              Gisselquist Technology, LLC
//              Gisselquist Technology, LLC
//
//
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//
//
// Copyright (C) 2015, Gisselquist Technology, LLC
// Copyright (C) 2015,2017, Gisselquist Technology, LLC
//
//
// This program is free software (firmware): you can redistribute it and/or
// This program is free software (firmware): you can redistribute it and/or
// modify it under the terms of  the GNU General Public License as published
// modify it under the terms of  the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or (at
// by the Free Software Foundation, either version 3 of the License, or (at
// your option) any later version.
// your option) any later version.
Line 34... Line 34...
// This program is distributed in the hope that it will be useful, but WITHOUT
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
// for more details.
//
//
 
// You should have received a copy of the GNU General Public License along
 
// with this program.  (It's in the $(ROOT)/doc directory.  Run make with no
 
// target there if the PDF file isn't present.)  If not, see
 
// <http://www.gnu.org/licenses/> for a copy.
 
//
// License:     GPL, v3, as defined and found on www.gnu.org,
// License:     GPL, v3, as defined and found on www.gnu.org,
//              http://www.gnu.org/licenses/gpl.html
//              http://www.gnu.org/licenses/gpl.html
//
//
//
//
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//
//
 
//
// Flash requires a minimum of 4 clocks per byte to read, so that would be
// Flash requires a minimum of 4 clocks per byte to read, so that would be
// 4*(4bytes/32bit word) = 16 clocks per word read---and that's in pipeline
// 4*(4bytes/32bit word) = 16 clocks per word read---and that's in pipeline
// mode which this prefetch does not support.  In non--pipelined mode, the
// mode which this prefetch does not support.  In non--pipelined mode, the
// flash will require (16+6+6)*2 = 56 clocks plus 16 clocks per word read,
// flash will require (16+6+6)*2 = 56 clocks plus 16 clocks per word read,
// or 72 clocks to fetch one instruction.
// or 72 clocks to fetch one instruction.
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        initial o_illegal = 1'b0;
        initial o_illegal = 1'b0;
        always @(posedge i_clk)
        always @(posedge i_clk)
                if ((o_wb_cyc)&&(i_wb_ack))
                if ((o_wb_cyc)&&(i_wb_ack))
                begin
                begin
                        o_valid <= (i_pc == o_wb_addr)&&(~i_wb_err);
                        o_valid <= (i_pc == o_wb_addr)&&(~i_wb_err);
                        o_illegal <= i_wb_err;
                        o_illegal <= (i_wb_err)&&(i_pc == o_wb_addr);
                end else if (i_stalled_n)
                end else if (i_stalled_n)
                begin
                begin
                        o_valid <= 1'b0;
                        o_valid <= 1'b0;
                        o_illegal <= 1'b0;
                        o_illegal <= 1'b0;
                end
                end

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