116 lines
3.2 KiB
Coq
116 lines
3.2 KiB
Coq
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/*
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* Copyright (c) 2000 Stephen Williams (steve@icarus.com)
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*
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* This source code is free software; you can redistribute it
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* and/or modify it in source code form under the terms of the GNU
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* General Public License as published by the Free Software
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* Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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/*
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* This program tests some tricky-to-compile strength syntax. Show that
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* gates can drive a wire with various strengths and be properly resolved.
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*/
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module main();
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reg pullval;
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wire (weak0, weak1) value = pullval;
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reg en0, en1;
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/* This buffer will drive a strong 1 to value if en0 is 1, otherwise
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it will go HiZ. */
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buf (highz0, strong1) drive0(value, en0);
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/* This inverter will drive a strong 0 to value if en1 is 1, otherwise
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is will go HiZ. */
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not (strong0, highz1) drive1(value, en1);
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initial begin
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en0 = 0;
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en1 = 0;
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/* Make sure when the other drivers are disabled, the pullval
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can pull the value up or down. The gates should be HiZ. */
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pullval = 1;
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#1 if (value !== 1'b1) begin
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$display("FAILED -- value is %b", value);
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$finish;
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end
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pullval = 0;
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#1 if (value !== 1'b0) begin
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$display("FAILED -- value is %b", value);
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$finish;
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end
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/* When en0 is 1, drive0 puts a strong 1 onto value so the
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pullval should not matter. */
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en0 = 1;
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pullval = 1;
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#1 if (value !== 1'b1) begin
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$display("FAILED -- en0==%b en1==%b pull==%b value==%b",
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en0, en1, pullval, value);
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$finish;
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end
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pullval = 0;
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#1 if (value !== 1'b1) begin
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$display("FAILED -- en0==%b en1==%b pull=0%b value==%b",
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en0, en1, pullval, value);
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$finish;
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end
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/* When en1 is 1, drive1 puts a strong 0 onto value so the
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pullval should not matter. */
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en0 = 0;
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en1 = 1;
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pullval = 1;
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#1 if (value !== 1'b0) begin
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$display("FAILED -- en0==%b en1==%b pull=0%b value==%b",
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en0, en1, pullval, value);
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$finish;
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end
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pullval = 0;
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#1 if (value !== 1'b0) begin
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$display("FAILED -- en0==%b en1==%b pull=0%b value==%b",
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en0, en1, pullval, value);
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$finish;
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end
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/* When both enables are 1, we have a double driven signal
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and the value should be x. */
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en0 = 1;
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en1 = 1;
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pullval = 1;
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#1 if (value !== 1'bx) begin
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$display("FAILED -- en0==%b en1==%b pull=0%b value==%b",
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en0, en1, pullval, value);
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$finish;
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end
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pullval = 0;
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#1 if (value !== 1'bx) begin
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$display("FAILED -- en0==%b en1==%b pull=0%b value==%b",
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en0, en1, pullval, value);
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$finish;
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end
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$display("PASSED");
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end // initial begin
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endmodule // main
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