Setting a variable inside a class

UVM
1

I am trying to achieve the following and am not sure how to do it. Any suggestions would be helpful.

  1. I have a base sequence item as follows:

   class base_seq_item extends uvm_sequence_item;
     `uvm_object_utils(base_seq_item);

      bit init_zero;
      bit init_rand;

     function new(string name="base_seq_item");
       init_zero = 0;
       init_rand = 0;
     endfunction
   endclass
  1. I have a bunch of other sequence items that extend from the above base_seq_item with each extended class having its own variables. Here’s an example extended sequence item class

    class ext_seq_item extends base_seq_item;
      `uvm_object_utils(ext_seq_item);

      rand logic [5:0] data;

      function new(string name="ext_seq_item");
        super.new(name);

        if(init_zero)
          data = 0;

        if(init_rand)
          data = $urandom();
      endfunction
    endclass

  1. The extended class constructor uses the variables init_zero and init_rand to set the initial value of the sequence item.

  2. I would like to know what is a way to set these variables (init_zero/init_rand) in the testbench (may be in build_phase) so that I can every sequence item object created sees this change. Is there any way to set this before creating the objects (afaik this is impossible in OOPs, but just checking)

2

You could make them static, but I am guessing you are looking for other possibilities.

3

In reply to KillSteal:

Making it static would result in the value being the same across all the child classes (in my case the extended sequence items). I would like to set different initial values (either 0/random) in different extended sequence item classes.

4

In reply to tpan:

This is what the uvm_config_db is for. You can put this in the base_seq_item constructor since the name will be overridden.

 function new(string name="base_seq_item");
       if (uvm_config_db::get(null,name,"init_zero",init_zero)) ; 
           else
         init_zero = 0;
       if (uvm_config_db::get(null,name,"init_rand",init_rand)) ; 
           else
         init_rand = 0;
     endfunction
5

In reply to dave_59:

Thanks for the response, Dave. I don’t quite get how can I use this. Let’s say I want for seq_item1 I want to set init_zero to 1 and for seq_item2 I want to set init_rand to 1, how can I do it (let’s say I want to do this from my test class)