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668 lvd 1 
// ZX-Evo Base Configuration (c) NedoPC 2008,2009,2010,2011,2012,2013,2014
425 lvd 2 
//
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// frame INT generation
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/*
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    This file is part of ZX-Evo Base Configuration firmware.
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    ZX-Evo Base Configuration firmware is free software:
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    you can redistribute it and/or modify it under the terms of
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    the GNU General Public License as published by
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    the Free Software Foundation, either version 3 of the License, or
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    (at your option) any later version.
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    ZX-Evo Base Configuration firmware is distributed in the hope that
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    it will be useful, but WITHOUT ANY WARRANTY; without even
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    the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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    See the GNU General Public License for more details.
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    You should have received a copy of the GNU General Public License
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    along with ZX-Evo Base Configuration firmware.
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    If not, see <http://www.gnu.org/licenses/>.
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*/
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30 lvd 24 
`include "../include/tune.v"
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module zint
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(
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        input  wire fclk,
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        input  wire zpos,
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        input  wire zneg,
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        input  wire int_start,
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        input  wire iorq_n,
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        input  wire m1_n,
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        input  wire wait_n,
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        output reg  int_n
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);
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        wire intend;
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        reg [9:0] intctr;
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        reg [1:0] wr;
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`ifdef SIMULATE
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        initial
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        begin
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                intctr = 10'b1100000000;
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        end
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`endif
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        always @(posedge fclk)
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                wr[1:0] <= { wr[0], wait_n };
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        always @(posedge fclk)
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        begin
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                if( int_start )
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                        intctr <= 10'd0;
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                else if( !intctr[9:8] && wr[1] )
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                        intctr <= intctr + 10'd1;
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        end
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        assign intend = intctr[9:8] || ( (!iorq_n) && (!m1_n) && zneg );
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        always @(posedge fclk)
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        begin
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                if( int_start )
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                        int_n <= 1'b0;
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                else if( intend )
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                        int_n <= 1'bZ;
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        end
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endmodule
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