uvm_sequence_item——sequence机制（一）

让子弹飞一会

　　UVM框架，将验证平台和激励分开，env以下属于平台部分，test和sequence属于激励，这样各司其职。我们可以将sequence_item 比喻成子弹，sequencer 类比成弹夹，UVM平台就是个枪。如图所示uvm_sequence 的类继承关系。

The sequence item is written by extending the uvm_sequence_item, uvm_sequence_item inherits from the uvm_object via the uvm_transaction class.

//------------------------------------------------------------------------------

//

// CLASS: uvm_sequence_item

//

// The base class for user-defined sequence items and also the base class for

// the uvm_sequence class. The uvm_sequence_item class provides the basic

// functionality for objects, both sequence items and sequences, to operate in

// the sequence mechanism.

//

//------------------------------------------------------------------------------

class uvm_sequence_item extends uvm_transaction;

  local      int                m_sequence_id = -;

  protected  bit                m_use_sequence_info;

  protected  int                m_depth = -;

  protected  uvm_sequencer_base m_sequencer;

  protected  uvm_sequence_base  m_parent_sequence;

  static     bit issued1,issued2;

  bit        print_sequence_info;

  // Function: new

  //

  // The constructor method for uvm_sequence_item.

  function new (string name = "uvm_sequence_item");

    super.new(name);

  endfunction

  function string get_type_name();

    return "uvm_sequence_item";

  endfunction

  // Macro for factory creation

  `uvm_object_registry(uvm_sequence_item, "uvm_sequence_item")

   ......

endclass

参考文献：

1 SequenceR and SequenceS. http://www.chipverify.com/uvm/sequencer-and-sequences

2 UVM Sequence item & Methods. http://www.verificationguide.com/p/uvm-sequence-item.html