In order for coverage data to be collected, the declared coverage groups must be instantiated. Similar to classes in OpenVera, the coverage_group serves as a template that can be instantiated whenever needed. The construct can be defined as a top-level (file scope) construct or may be contained inside of a class.

There are two types of instantiation based on definition of coverage_group.

• Standalone Coverage Group : Once defined, a standalone coverage_group must be explicitly instantiated using the new() system call for coverage to be triggered.
• Instantiating Embedded Coverage Groups : Embedded coverage groups can be instantiated in one of two ways, either explicitly or implicitly. In addition, they can also be disabled using the null assignment statement.

  1 class coverage_covergroup {
  2   // All variables declared here
  3   integer abc;
  4   bit [7:0] data;
  5 
  6   // Declare coverage_groups here
  7   coverage_group c1 {
  8      sample_event = wait_var(abc);
  9      // Body of coveragegroup here
 10      sample data;
 11    
 12   }
 13 
 14   // All the class methods here
 15   task new () {
 16     // There is no new on coverage_group here
 17   }
 18 }
 19 
 20 program test {
 21   coverage_covergroup cov = new();
 22 }

  1 class coverage_explicit {
  2   bit [3:0] value;
  3   event     now;
  4 
  5   coverage_group something {
  6      sample_event = sync(ALL,now);
  7      sample value;
  8   }
  9 
 10   task new () {
 11     // Do explicit new on covergroup
 12     something = new();
 13   }
 14 
 15   task update_coverage (bit [3:0] value) {
 16      this.value = value;
 17      trigger(now);
 18   }
 19 }
 20 
 21 program test {
 22   coverage_explicit cov = new();
 23   bit [3:0] v; 
 24   repeat (10) {
 25     v = random();
 26     printf("Value is %d\n",v);
 27     cov.update_coverage(v);
 28     delay(1);
 29   }
 30 }    

  1 class coverage_null {
  2   bit [3:0] value;
  3   event     now;
  4 
  5   coverage_group something {
  6      sample_event = sync(ALL,now);
  7      sample value;
  8   }
  9 
 10   task update_coverage (bit [3:0] value) {
 11      this.value = value;
 12      trigger(now);
 13   }
 14 }
 15 
 16 program test {
 17   coverage_null cov = new();
 18   bit [3:0] v; 
 19   // Disable coverage collection
 20   cov.something = null;
 21   repeat (10) {
 22     v = random();
 23     printf("Value is %d\n",v);
 24     cov.update_coverage(v);
 25     delay(1);
 26   }
 27 }    

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