Cross Coverage Qs.

[Gurijala Shashank]

In the covegroup tab, cross bins ad12,ad13,ad14,ad15 are not created at all where as bins ad22,ad23,ad24,ad25 are created. WHY?

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Code Verilog - [expand]
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c1: coverpoint addr {
bins a1    =  {0,1,2,3};
bins a2[]  =  {[4:7]};
bins a3[2] =  {[5:8],[9:11],12};
bins a4[]  =  {[13:$]};
bins a5[]  =  (0 => 6[*2] => 10);
}
 
c2: coverpoint data {
bins d1[]   =  {0,1,2,3,4,5};
bins d2[2]  =  {[6:15],[16:30]};
bins d3     =  {[31:50]};
bins d4[]   =  {51,52,53,54,55,[56:100]};
bins d5     =  {[100:$]};
bins d6     =  (55 => 10 => 12,18 => 10[=3]);
}
 
c3: cross c1,c2 {
bins ad12   =   binsof(c1.a1) && binsof(c1.a2);
bins ad13   =   binsof(c1.a1) && binsof(c1.a3);
bins ad14   =   binsof(c1.a1) && binsof(c1.a4);
bins ad15   =   binsof(c1.a1) && binsof(c1.a5);
bins ad16   =   binsof(c1.a1) && binsof(c2.d1);
bins ad17   =   binsof(c1.a1) && binsof(c2.d2);
bins ad18   =   binsof(c1.a1) && binsof(c2.d3);
bins ad19   =   binsof(c1.a1) && binsof(c2.d4);
bins ad20   =   binsof(c1.a1) && binsof(c2.d5);
bins ad21   =   binsof(c1.a1) && binsof(c2.d6);
bins ad22   =   binsof(c1.a1) || binsof(c1.a2);
bins ad23   =   binsof(c1.a1) || binsof(c1.a3);
bins ad24   =   binsof(c1.a1) || binsof(c1.a4);
bins ad25   =   binsof(c1.a1) || binsof(c1.a5);
bins ad26   =   binsof(c1.a1) || binsof(c2.d1);
bins ad27   =   binsof(c1.a1) || binsof(c2.d2);
bins ad28   =   binsof(c1.a1) || binsof(c2.d3);
bins ad29   =   binsof(c1.a1) || binsof(c2.d4);
bins ad30   =   binsof(c1.a1) || binsof(c2.d5);
bins ad31   =   binsof(c1.a1) || binsof(c2.d6);
}

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[nand_gates]

Because the bins are mutually exclusive {c1.a1, c1.a2, c1.a3, c1.a4, c1.a5} i.e. no two will be true at a time hence their anding
will be false always and you see no bins created! Hope you got it!