Using the UVM Factory

🔍 Introduction

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The UVM Factory is a powerful mechanism in the UVM testbench architecture that enables dynamic and flexible object and component creation. Thanks to the factory, you can decide at runtime which implementation of a base class will be instantiated. This dramatically increases the reusability and flexibility of your testbench.

🏭 What is UVM Factory?

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UVM Factory is an implementation of the factory design pattern that allows:

• Multiple derived classes for a single base class.
• The factory determines which derived class to instantiate at runtime.
• Different implementations can be loaded via configuration or in the test phase.

🔨 Registering with the Factory

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To make a class available to the UVM Factory, you use the uvm_component_utils or uvm_object_utils macros:

class my_driver extends uvm_driver #(my_transaction);
  `uvm_component_utils(my_driver)
  // ...
endclass

This registers the my_driver class with the factory.

🔄 Using Factory Overrides

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One of the biggest advantages of the UVM Factory is its override capability:

uvm_factory::get().set_type_override_by_type(base_type::get_type(), derived_type::get_type());

Or using name-based overrides:

uvm_factory::get().set_type_override_by_name("base_type", "derived_type");

This ensures that whenever the base type is requested, the derived type is instantiated instead.

📦 Example: Factory Override

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Here’s an example of how to override a monitor class with a coverage-enabled version during a test:

initial begin
  uvm_factory::get().set_type_override_by_name("my_monitor", "my_coverage_monitor");
end

With this line, whenever "my_monitor" is requested, the "my_coverage_monitor" class will be created.

🎯 Why Use UVM Factory?

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✅ Flexibility: Change testbench behavior at runtime with different configurations.
✅ Reusability: Try different derived classes using the same base type.
✅ Maintainability: Swap implementations without changing testbench code.

🚀 Creating with the Factory

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Components and objects are typically instantiated using the factory’s create() methods, which apply overrides automatically:

my_driver drv;
drv = my_driver::type_id::create("drv", this);

This call returns an instance of the correct class, including any registered overrides.

📌 Conclusion

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The UVM Factory adds flexibility and configurability to your testbench environment. Use it to dynamically swap or extend components without rewriting code.