50 lines
1.2 KiB
Coq
50 lines
1.2 KiB
Coq
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module main;
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// Model a pin with a weak keeper circuit. The way this works:
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// If the pin value is 1, then attach a weak1 pullup, but
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// if the pin value is 0, attach a weak0 pulldown.
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wire pin;
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pullup (weak1) (keep1);
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pulldown (weak0) (keep0);
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tranif1 (pin, keep1, pin);
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tranif0 (pin, keep0, pin);
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// Logic to drive a value onto a pin.
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reg value, enable;
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bufif1 (pin, value, enable);
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initial begin
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value = 0;
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enable = 1;
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#1 if (pin !== 0) begin
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$display("FAILED -- value=%b, enable=%b, pin=%b", value, enable, pin);
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$finish;
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end
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// pin should hold its value after the drive is removed.
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enable = 0;
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#1 if (pin !== 0) begin
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$display("FAILED -- value=%b, enable=%b, pin=%b", value, enable, pin);
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$finish;
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end
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value = 1;
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enable = 1;
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#1 if (pin !== 1) begin
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$display("FAILED -- value=%b, enable=%b, pin=%b", value, enable, pin);
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$finish;
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end
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// pin should hold its value after the drive is removed.
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enable = 0;
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#1 if (pin !== 1) begin
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$display("FAILED -- value=%b, enable=%b, pin=%b", value, enable, pin);
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$finish;
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end
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$display("PASSED");
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end
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endmodule // main
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