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// ZX-Evo Base Configuration (c) NedoPC 2014
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//
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// CMOS emulator: cmos is needed for zxevo.rom to function correctly
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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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module cmosemu
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(
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        input  wire       zclk,
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        input  wire       cmos_req,
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        input  wire [7:0] cmos_addr,
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        input  wire       cmos_rnw,
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        output reg  [7:0] cmos_read,
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        input  wire [7:0] cmos_write
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);
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        reg [7:0] mem [0:239];
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        reg req_r;
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        function [7:0] cmos_rd
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        (
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                input [7:0] addr
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        );
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                if( addr<8'd240 )
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                        cmos_rd = mem[addr];
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                else
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                        cmos_rd = 8'hFF;
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        endfunction
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        task cmos_wr
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        (
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                input [7:0] addr,
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                input [7:0] data
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        );
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                if( addr<8'd240 )
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                        mem[addr] <= data;
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        endtask
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        initial
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        begin
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                int i;
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                for(i=0;i<256;i=i+1)
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                        mem[i] <= 8'd0;
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        end
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        always @(posedge zclk)
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                req_r <= cmos_req;
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        always @(posedge zclk)
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        begin
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                cmos_read <= cmos_rd(cmos_addr);
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                if( req_r && !cmos_rnw )
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                        cmos_wr(cmos_addr,cmos_write);
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        end
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endmodule
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