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cannot pass uvm_sequence_item to send_to_dut

Sporadic Crash

Hi all,

Problem: I cannot call within uvm_driver the method send_to_dut with uvm_sequence_item. send_to_dut without argument can access class items of uvm_sequence_item, though.

My example is based on the forum entries run_phase doesn't update SV interface signals and How to use uvm_agent for sequencing . In the original case following done, which is working;

class my_transaction extends uvm_sequence_item;
  rand logic [7:0] load_val;
...
endclass

...

class my_driver extends uvm_driver #(my_transaction);
...
virtual task run_phase(uvm_phase_phase);
  seq_item_port.get_next_item(req);
  send_to_dut();
  seq_item_port.item_done();
endtask

virtual task send_to_dut();
  dut_vi.i_load_val = req.load_val;
endtask

The code above works. Please note that send_to_dut does not take an argument. However if I use

send_to_dut ( req );

and

virtual task send_to_dut (uvm_sequence_item my_req);
dut_vi.i_load_val = my_req.load_val;

... then Incisive complains that load_val in the sent_to_dut task is not a class item.

Where is my mistake?

  • The uvm_driver has a class variable "req" whose type you specify when you created your own driver class. In my_driver, you said it was type "my_transaction" when you specified "...extends uvm_driver #(my_transaction):". However, in your virtual method declaration, you declared an input argument of type "uvm_sequence_item". 

    For the default send_to_dut, "req" is referring to the class variable of type my_transaction. So it has a field load_val. In your specialized send_to_dut method, your argument "my_req" is declared to be of the vanilla type uvm_sequence_item. That does not have a field of type load_val.

    Either typecast the sequence_item handle:

    virtual task send_to_dut (uvm_sequence_item my_req);
    my_transaction send_req;
    $cast(send_req,my_req);
    dut_vi.i_load_val = send_req.load_val;

    Or, change your argument type:

    virtual task send_my_trans_to_dut ( my_transaction my_req );
    ...

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