Nonblocking Events

Refer to SystemVerilog Events before going through this section.

Non-blocking event is triggered using ->>

As discussed in an earlier example,

In case of waiting for an event using @ operator, an event will be missed if the event is triggered (using ->) at the same time as waiting for the event trigger.

The non-blocking event (using –>>) is triggered in the non-blocking region of the time slot. Ultimately, event triggering using ->> is a delayed version of the event triggering using ->. Hence, the process_B was waiting for the event using @ operator is completed as shown in the below example.

module event_example();
  event e1;

  task process_A();
    $display("@%0t: process_A: Before triggering event e1 using ->>", $time);
    ->>e1;
    $display("@%0t: process_A: After triggering event e1 using ->>", $time);
  endtask
  
  task process_B();
    $display("@%0t: process_B: waiting for the event e1", $time);
    @(e1.triggered);
    $display("@%0t: process_B: event e1 is triggered", $time);
  endtask

  initial begin
    fork
      process_A();
      process_B();
    join
  end
endmodule

Output:

@0: process_A: Before triggering event e1 using ->>
@0: process_A: After triggering event e1 using ->>
@0: process_B: waiting for the event e1
@0: process_B: event e1 is triggered

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