RISE_OBJECTION, DROP_OBJECTION AND SET_DRAIN_TIME - NISHUNISARGA/UVM_notes GitHub Wiki

In UVM (Universal Verification Methodology), raise_objection and drop_objection are methods used to control the duration of simulation phases, especially the run_phase. They are part of the UVM phase objection mechanism, which ensures that a phase doesn’t end until all components are done with their tasks/work.

Purpose

raise_objection: Signals that a component is still performing its tasks and the current phase should not end.
drop_objection: Signals that the component has completed its tasks and is ready for the phase to end. These methods allow multiple components to synchronize their activities during a phase.

How It Works

when the UVM phase (like run_phase) starts, the Components can raise objections to indicate they are working on tasks/functionality in that phase.
The phase continues to work as long as the active objections are present.
Once all objections are dropped, the phase ends and moves to the next phase.

when to use

raise the objection before starting the components' activities/work/tasks/functionality.
drop the objection once all the activities are completed

where we can all them

we can call them from any uvm component(test,env,agent,monitor,driver,scoreboard,sequence)

In env

The environment often manages objections for the overall testbench, ensuring the run_phase does not end prematurely (means Managing the global behavior of the testbench and ensuring all agents, monitors, and sequences are complete before the run_phase ends.)

example:

      class my_env extends uvm_env;
         task run_phase(uvm_phase phase);
             phase.raise_objection(this);
                 `uvm_info("ENV", "Starting environment tasks", UVM_LOW); // Perform some tasks
             #100;
             phase.drop_objection(this);
         endtask
       endclass

In driver

Any UVM component can raise and drop objections to ensure it completes its work before the phase ends(When generating stimulus or waiting for responses. To ensure the run_phase doesn’t end while the driver is still processing).

example:

      class my_driver extends uvm_driver;

         task run_phase(uvm_phase phase);
            phase.raise_objection(this);
              `uvm_info("DRIVER", "Driving stimulus", UVM_LOW);
               repeat (10) begin
                   drive_tx();
                   #10;
               end
            phase.drop_objection(this);
         endtask
       endclass

In Sequence

Sequences often raise objections to keeping the run_phase active while generating stimulus.

example:

      class my_sequence extends uvm_sequence;
         
           task body();
              phase.raise_objection(this);
              `uvm_info("SEQUENCE", "Starting of objection", UVM_LOW);

                start_item(txn);
                finish_item(txn);
                phase.drop_objection(this);
                `uvm_info("SEQUENCE", "end of objection", UVM_LOW);
            endtask
        endclass

In Monitor or Scoreboard
- To allow post-processing or data analysis even after the stimulus is complete.
In UVM_test

RISE_OBJECTION, DROP_OBJECTION AND SET_DRAIN_TIME - NISHUNISARGA/UVM_notes GitHub Wiki

Purpose

How It Works

when to use

where we can all them

In UVM_test