Excluding the already defined bins

Coverage
, ,
1

I am trying to create a bin & exclude the same bin value when specific variable is not set .
I’ve tried below 3 options but none of them making coverage score to 100%.

  bit  x, decider;  // If decider is 1, then only X can be covered

  Approach 1 :  
--------------------
  x_cp : coverpoint x iff (decider == 1) {
      bins HIT = {1};
  }

  Approach 2 :  
--------------------
  x_cp : coverpoint x {
      bins HIT = {1} iff (decider == 1);
  }

  Approach 1 :  
--------------------
  x_cp : coverpoint x {
      bins HIT = {1};
      ignore_bins IGNORE_HIT = {1} iff (decider == 0);
  }
2

The iff construct of a cover group, point, or bin only blocks sampling, not construction of the bins. You can achieve 100% coverage by either adding a decider to the coverpoint expression or setting its weight to zero.

cg_inst.x_cp.option.weight = 0;

or

x_cp : coverpoint x || (decider == 0) {
      bins HIT = {1};
 }
3

Thanks @dave_59 . Can weight be dynamically set to 0 ?
I tried doing it in EDA Playground, but it’s not working .

4

Please explain what “not working” means. Show us your example.

5

Sure . Below is my example

covergroup cg_y @(posedge clk);     
    a_y : coverpoint y {       
       option.weight = 0;       
       bins HIT = {1};            
    }
endgroup


initial begin
    cg_y cg_inst_y = new();
    decider = 0;y = 0;
    for (int i = 0; i < 14; i++) begin
        #10;
    end
    $display (“Coverage_Y = %0.2f %%”, cg_inst_y.get_coverage());
    $finish();
end

In the above, coverage score is still 0%.
Can you please check ?

6

To use a weight=0, you must have at least one other coverpoint or covergroup with 100% coverage. If not, you’ll need to use my second approach. Regardless of the approach, you’ll need to sample your covergroup.

Here is an example of a complete ready to run example

module top;
  logic y, decider;
  
  covergroup cg_y;
    a_y : coverpoint y {       
      bins HIT = {1};            
    }
    b_y: coverpoint y { 
      bins HIT = {0};            
    }
  endgroup

  cg_y cg_inst_y = new();

  initial begin
    decider = 0;y = 0;
    cg_inst_y.sample();
    $display ("Coverage_Y = %5.2f %%", cg_inst_y.get_coverage());
    if (decider == 0)
      cg_inst_y.a_y.option.weight = 0;
    $display ("Coverage_Y = %5.2f %%", cg_inst_y.get_coverage());
  end
endmodule