Encore SIM EDITOR SOFTWARE Guide de l'utilisateur télécharger pdf (Page 124)

3-16

Compiling and Elaborating Your Design

Filtering Out False Negatives

By default, if a signal in a conditional expression transitions to an X

or Z value and then to 0 or 1 in the same simulation time step, VCS

displays the warning.

Example 1

In this example, VCS displays the warning message when reg r1

transitions from 0 to X to 1 during simulation time 1.

Example 4 False Negative Example

module test;

reg r1;

initial

begin

r1=1'b0;

#1 r1=1'bx;

#0 r1=1'b1;

end

always @ (r1)

begin

if (r1)

$display("\n r1 true at %0t\n",$time);

else

$display("\n r1 false at %0t\n",$time);

end

endmodule

Example 2

In this example, VCS displays the warning message when reg r1

transitions from 1 to X during simulation time 1.

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Encore SIM EDITOR SOFTWARE Guide de l'utilisateur Page 124