How to write coverage for a an array?

UVM
, , ,
1

How to write functional coverage for an array of 128 elements where each element is of 8-bit width?

Example:
rand bit [7:0]data[127:0];

I want to check if any value between {8’d1,8’d2,8’d4,8’d8,8’d16,8’d32,8’d64,8’d128,8’d255} is covered or not for each element of the array i.e. for 128 elements and display the 128 bins info

2

In reply to djmandela:

Maybe you can do something like this

module array_covergroup_test();

  bit [7:0] data[127:0];
  
  bit [7:0] values [$] = {8'd1,8'd2,8'd4,8'd8,8'd16,8'd32,8'd64,8'd128,8'd255};
  
  covergroup array_cg with function sample (int index);
    
    element_inside_cp : coverpoint (data[index] inside {values}) {
      bins valid  = {1};  
    }    
    
  endgroup
  array_cg cg;
  initial begin
    cg = new();
    foreach (data[i]) begin
      data[i] = $urandom_range(0, 255);
      cg.sample(i);
    end
    $display("array_cg instance coverage = %0f", cg.get_inst_coverage());
  end
  
endmodule

HTH,
-R

3

Thank you, but can we generate separate bins for each value

4

In reply to djmandela:

This is another implementation, where bin is created for each values per index basis.

module array_covergroup_test();

   bit [7:0] data[127:0] ;
   bit [7:0] values [$] = {8'd1,8'd2,8'd4};

   covergroup array_cg (int index);
       option.per_instance = 1;
       coverpoint data[index] {
           bins value[] =  {8'd1,8'd2,8'd4}; //{values};
	}
   endgroup

   array_cg cg[128];

   initial begin
      foreach(cg[i])begin
        cg[i] = new(i);
      end

      repeat(100)begin
	 std::randomize(data);
	 foreach(cg[i])begin
	    cg[i].sample();
	 end
      end 
   end 
   
endmodule // array_covergroup_test
5

In reply to djmandela:

I understood you wanted to cover if any of the array values was in the set you mentioned, yourcheers’ solution is what you are probably looking for.

6

Thanks a lot!

7

Yes it works. I actually wanted to check if each bit of the variable “data” toggles or not that too for the entire depth of the array (128).