cross is used for creating permutation and combitation of state and tran bins creater in coverage group. Basically this is used for creating more deep functional coverage points.

Lets assume we have

• variable a which is 1 bit wide and states are S0 and S1
• variable b whish is also is 1 bit wide and states are M0 and M1
• when we do cross on samples of a and b it creates S0M0, S0M1, S1M0, S1M1.
• Basically it means when S0 occured, did M0 occured, same for other states

  1 class coverage_cross {
  2   bit [1:0] value1;
  3   bit [1:0] value2;
  4   event     now;
  5 
  6   coverage_group something {
  7      sample_event = sync(ALL,now);
  8      sample value1,value2;
  9      cross MY_CROSS (value1,value2);
 10   }
 11 
 12   task update_coverage (bit [1:0] value1,bit [1:0] value2) {
 13      this.value1 = value1;
 14      this.value2 = value2;
 15      trigger(now);
 16   }
 17 }
 18 
 19 
 20 
 21 program test {
 22   coverage_cross cov = new();
 23   bit [1:0] v1; 
 24   bit [1:0] v2; 
 25   repeat (10) {
 26     v1 = random();
 27     v2 = random();
 28     printf("Value is %0d %0d\n",v1,v2);
 29     cov.update_coverage(v1,v2);
 30     delay(1);
 31   }
 32 }    

 Value is 0 1
 Value is 3 1
 Value is 1 2
 Value is 2 3
 Value is 3 1
 Value is 2 3
 Value is 1 2
 Value is 2 0
 Value is 0 3
 Value is 2 2

 Group : test::coverage_cross::something
 
 ====================================================
 Group : test::coverage_cross::something
 ====================================================
 Score   Weight  Goal    
  81.25  1       100     
 
 
 
 
 ====================================================
 
 Samples for Group : test::coverage_cross::something
 
 
 
 Variable Expected Covered Percent Goal Weight 
                                               
 Total    8        8       100.00              
                                               
 value1   4        4       100.00  100  1      
                                               
 value2   4        4       100.00  100  1      
                                               
 
 
 Crosses for Group : test::coverage_cross::something
 
 
 
 Cross    Expected Covered Percent Goal Weight 
                                               
 Total    16       7       43.75               
                                               
 MY_CROSS 16       7       43.75   100  1      
                                               
 
 
 ====================================================
 
 Summary for variable value1
 
 
                              Expected Covered Percent 
                                                       
 Automatically Generated Bins 4        4       100.00  
                                                       
 
 
 Automatically Generated Bins for value1
 
 
 Bins
 
 name    count at least  
                        
 auto[0] 2     1        
                        
 auto[1] 2     1        
                        
 auto[2] 4     1        
                        
 auto[3] 2     1        
                        
 
 
 ====================================================
 
 Summary for variable value2
 
 
                              Expected Covered Percent 
                                                       
 Automatically Generated Bins 4        4       100.00  
                                                       
 
 
 Automatically Generated Bins for value2
 
 
 Bins
 
 name    count at least  
                        
 auto[0] 1     1        
                        
 auto[1] 3     1        
                        
 auto[2] 3     1        
                        
 auto[3] 3     1        
                        
 
 
 ====================================================
 
 Summary for cross MY_CROSS
 
 
 Samples crossed: value1 value2
                                    Expected Covered Percent Missing 
                                                                     
 Automatically Generated Cross Bins 16       7       43.75   9       
                                                                     
 
 
 Automatically Generated Cross Bins for MY_CROSS
 
 
 Uncovered bins
 
 value1    value2              count at least          
                                                       
 [auto[0]] [auto[0]]           0     1        
                                              
 [auto[0]] [auto[2]]           0     1        
                                              
 [auto[1]] [auto[0] - auto[1]] --    --       (2 bins) 
                                                       
 [auto[1]] [auto[3]]           0     1        
                                              
 [auto[2]] [auto[1]]           0     1        
                                              
 [auto[3]] [auto[0]]           0     1        
                                              
 [auto[3]] [auto[2] - auto[3]] --    --       (2 bins) 
                                                       
 
 
 Covered bins
 
 value1  value2  count at least  
                                
 auto[2] auto[2] 1     1        
                                
 auto[2] auto[0] 1     1        
                                
 auto[2] auto[3] 2     1        
                                
 auto[0] auto[3] 1     1        
                                
 auto[0] auto[1] 1     1        
                                
 auto[1] auto[2] 2     1        
                                
 auto[3] auto[1] 2     1        
                                
 
 

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