uvm_sequence

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squence由data item组成， 不同的组合可以产生不同的transaction， 所以便可以产生不同的激励。如下图所示：

下面是使用sequence的步骤：

  1. 创建一个自定义的sequence， 派生自[uvm_sequence]。 用factory机制注册， 并且创建new函数：
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// my_sequence is user-given name for this class that has been derived from "uvm_sequence"
class my_sequence extends uvm_sequence;
 
  // [Recommended] Makes this sequence reusable. Note that we are calling 
  // `uvm_object_utils instead of `uvm_component_utils because sequence is a uvm_transaction object
  `uvm_object_utils (my_sequence)
 
  // This is standard code for all components
    function new (string name = "my_sequence");
      super.new (name, parent);
    endfunction  
endclass
  1. 申明默认的sequencer来执行sequence的transaction：
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// [Optional] my_sequencer is a pre-defined custom sequencer before this sequence definition
`uvm_declare_p_sequencer (my_sequencer)
  1. 定义body
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// [Recommended] Make this task "virtual" so that child classes can override this task definition
virtual task body ();
  // Stimulus for this sequence comes here
endtask