usage of get_trigger_data()

[Mital]

Hi All,
I am facing the following issue while using get_trigger_data() to get the data associated with the last trigger event.

When I use get_trigger_data(), after wait_trigger(), I am getting the correct value of data. Now, I change the field of packet "data2.sfd =1". After this, I am again calling get_trigger_data() in other task. Then why the updated value of sfd is displayed? According to the functionality, get_trigger_data() should reflect the data associated with a last trigger event.

I have tried the following code:

import ovm_pkg::*;
`include "ovm_macros.svh"

class packet extends ovm_sequence_item;
  rand bit [7:0] sfd;
  `ovm_object_utils_begin(packet)
    `ovm_field_int(sfd, OVM_ALL_ON)
  `ovm_object_utils_end
   function new (string name = "packet");
     super.new(name);
   endfunction : new
endclass: packet

class bfm_c extends ovm_driver;
   packet data1;
   packet data2;
   packet data3;
   ovm_object datax;
   ovm_object datax1;
   ovm_event ack_process;
  `ovm_component_utils(bfm_c)

  function new(string name ="", ovm_component parent);
     super.new(name, parent);
     ack_process  = new("ack");
     data1  = new("data1");
     data2  = new("data2");
     data3  = new("data3");
  endfunction

  task run;
    fork
     begin #1;
      ack_process.wait_trigger();
      datax = ack_process.get_trigger_data();
      $cast(data2,datax);
      $display("After wait data2.sfd=%d", data2.sfd); 
      data2.sfd=1;
     end
     begin #4;
      void'(data1.randomize());
      ack_process.trigger(data1);
     end
   join
   task_1();
  endtask

  task task_1;
  begin
    datax1 = ack_process.get_trigger_data();
    $cast(data3,datax1);
    $display("data3.sfd=%d", data3.sfd); 
  end
  endtask
endclass : bfm_c

module top;
  bfm_c e;
  initial begin e = new("bfm_c",null); run_test();
  end
endmodule

Is this the expected behaviour of get_trigger_data()? Please let me know about this.

Thanks,
Mital

[dlong]

Hi Mital,

ack_process.get_trigger_data() returns a class handle. $cast copies the class handle to your data2 variable. Anything you do to data2 is actually being done to the object you originally passed into the ovm_event via the call to trigger.

If you want to modify data2 without changing the ovm_event data you should copy or clone the returned object, e.g.

  $cast( data2,datax.clone() );

Regards,
Dave