Requirement of objections in UVM

[anshulgarg]

Hi,

 

I have a doubt about requirement of raise/drop_objection.

 

Why does a compiler need objections in run_phase?

 

Why can it not just wait for time given like 100ns as following example?

 

Ex. 

task run_phase(uvm_phase phase);

  //phase.raise_objection(this);     

  #100ns;

  //phase.drop_objection(this);    

endtask 

 

   

[bhunter1972]

Some components may have a run-time phase which operates in a "Run forever and wake up when there's something to do" mode, like this simplistic driver:

virtual task run_phase(uvm_phase phase);
   forever begin
      seq_item_pull_port.get(req);
      
      phase.raise_objection(phase);
      drive_my_request(req);
      phase.drop_objection(phase);
   end
endtask : run_phase

When there are no objections remaining, all of the tasks spawned by all of the component's run phases are killed. This is a feature, not a bug.

 

It just wouldn't do to kill this task's run phase while it was driving a request. And UVM cannot implicitly know how long that will take. Therefore, the objection software pattern is used for all run-time phases.

[hrishikeshadn]

Mainly the objections are used in testcases, which helps in simulation to end after your sequences or intented operations are performed.Hard coded delays are not good to use, because when you are doing Constaint Random testing we can't predict completion time.I think I answered your question