UVM Base Classes

The UVM library is built on a hierarchy of base classes that form the foundation for all UVM components. These classes provide essential features that make UVM powerful and flexible.

🏗️ UVM Class Hierarchy
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This section presents the class hierarchy of UVM. It clearly shows the base classes and which classes are derived from which.

uvm_void
└── uvm_object
    ├── uvm_transaction
    ├── uvm_sequence_item
    ├── uvm_sequence_base
    └── uvm_component
        ├── uvm_test
        ├── uvm_env
        ├── uvm_agent
        ├── uvm_driver
        ├── uvm_monitor
        └── uvm_sequencer

🪝 uvm_void
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This class sits at the top of the UVM class tree and is an abstract class with no data members or functions.

✨ Key Features
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virtual class uvm_void;
  // 🔹 Base abstract class for all UVM classes.
  // 🔹 Contains no members or methods by default.
endclass

📦 uvm_object
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uvm_object is the base class for all UVM objects. It includes basic object operations such as copying, comparing, and printing.

✨ Key Features
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virtual class uvm_object extends uvm_void;

  // 🔹 Constructor: creates a new object with an optional name
  extern function new(string name = "");

  // 🔹 Returns the object's local name
  extern virtual function string get_name();

  // 🔹 Returns the object's full hierarchical name
  extern virtual function string get_full_name();

  // 🔹 Returns the object's type wrapper (note: static)
  extern static function uvm_object_wrapper get_type();

  // 🔹 Creates a new object dynamically via the factory
  virtual function uvm_object create(string name=""); 
    return null; 
  endfunction

  // 🔹 Clones (deep copies) the object
  extern virtual function uvm_object clone();

  // 🔹 Copies values from another object of the same type
  extern function void copy(uvm_object rhs);

  // 🔹 Compares this object to another object
  extern function bit compare(uvm_object rhs, uvm_comparer comparer=null);

  // 🔹 Prints the object's contents
  extern function void print(uvm_printer printer=null);

  // 🔹 Converts the object to a string representation
  extern virtual function string convert2string();

endclass

🗂️ uvm_root
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uvm_root is the global manager of the UVM testbench. It uses the singleton pattern to manage test execution and phase control.

✨ Key Features
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class uvm_root extends uvm_component;

  // 🔹 Returns the singleton instance of uvm_root
  static function uvm_root get();

  // 🔹 Starts the specified test and manages phase control
  virtual task run_test (string test_name="");

  ...
endclass

🏗️ uvm_component
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uvm_component is the base class for all testbench components. It includes build, connect, and run phase methods.

✨ Key Features
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virtual class uvm_component extends uvm_report_object;

  // 🔹 Constructor: creates the component with its name and parent
  function new (string name, uvm_component parent);

  // 🔹 Main simulation phase where component functionality is implemented
  virtual task run_phase(uvm_phase phase);

  // 🔹 Phase for building sub-components and setting up configurations
  virtual function void build_phase(uvm_phase phase);

  // 🔹 Phase for connecting TLM ports and interfaces
  virtual function void connect_phase(uvm_phase phase);

  ...
endclass