CODEWITHSUNDEEP
system-verilog
Sanjeev Singh
Sanjeev Singh

Reputation: 151

Sampling covergroup from another class in systemverilog

I want to instrument my system verilog model for collecting functional coverage on the packets it processes. Specifically, I want to see of the distribution of the packet length in the incoming packet. However, my naive attempt gives "null reference" on sample method below. What is the way to do this?

class packet;
     rand bit[7:0] len;
     covergroup packet_len_cg;
       coverpoint len;
     endgroup 
 endclass

class model;
  // Scoreboard calls this to process the input packet
  function void run(packet p1);
    p1.packet_len_cg.sample(); //FAILS WITH NULL REFERENCE!!
  endfunction
endclass

module test;
  model m1;
  packet p1;
  initial begin
    m1 = new();
    p1 = new();
    assert(p1.randomize());
    m1.run(p1);
  end
endmodule

My code on edaplayground https://www.edaplayground.com/x/2VPm

Upvotes: 1

Views: 1181

Answers (1)

dave_59
dave_59

Reputation: 42738

You need to construct the covergroup.

class packet;
     rand bit[7:0] len;
     covergroup packet_len_cg;
       coverpoint len;
     endgroup 
     function new;
        packet_len_cg = new;
     endfunction
 endclass

Upvotes: 2

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