Introduction
Introduction Get started Hello UVM example UVM Phases Part 1 UVM Phases Part 2 UVM Base Classes UVM Object and Core Methods UVM Components
Building a Testbench
UVM Transaction UVM Sequence UVM Sequencer UVM Driver UVM Monitor UVM Scoreboard UVM Agent UVM Environment UVM Test
Other Components
Coverage Collector
Execution Model
UVM Phases Objections
Communication
TLM Basics TLM Blocking Put Port TLM Non-Blocking Put Port TLM Blocking Peek Port Analysis Ports TLM FIFO
Configuration
UVM Factory UVM Config DB
Runtime Control
UVM Plusargs Seeds & Reproducibility Verbosity Control Debug Runtime Controls
Advanced
Virtual Sequences Virtual Sequencer
UVM RAL
Intro Abstraction Flexibility Comparison Coverage Minimum Requirements Learning Path Register Types First Implementation Register with 2 Fields Register with Reserved Bits Access Policies Part 1 Access Policies Part 2 Access Policies Part 3 Access Policies Part 4 Memory Modeling Register Block Adapter Introduction Adapter Methods Adapter Example Predictor Types Desired and Mirror Values Register Methods Desired Value Mirror Value

UVM Object and Core Methods

uvm_object is the base class for most non-component UVM classes. It provides essential functionality such as printing, copying, comparing, packing, unpacking, and factory-based object creation.

What is uvm_object?

uvm_object is the base class for:

  • Sequence items
  • Sequences
  • RAL objects
  • Configuration objects
  • Transaction-level data structures
Important: uvm_object does NOT have phases and does NOT live in the UVM hierarchy. It is lightweight and used mainly for data modeling.

Core Methods of uvm_object

The power of uvm_object comes from its built-in utility methods. These methods enable automation and consistency in verification environments.

1️⃣ create()

Used for factory-based object creation. 

my_item item;
item = my_item::type_id::create("item");

This enables factory overrides and polymorphism.

2️⃣ copy()

Copies the contents of one object into another. 

item2.copy(item1);

Internally calls do_copy(), which users can override.

3️⃣ compare()

Compares two objects field-by-field. 

if (item1.compare(item2))
  `uvm_info("COMPARE", "Objects match", UVM_LOW)

Internally calls do_compare(). Extremely useful in scoreboards.

4️⃣ print()

Prints object fields using a printer policy. 

item.print();

Internally calls do_print(). Useful for debugging transactions.

5️⃣ pack() / unpack()

Converts object data into a bitstream and vice versa. 

bit bits[];
item.pack(bits);
item.unpack(bits);

Internally calls:

  • do_pack()
  • do_unpack()

Used in predictors, reference models, and advanced TLM use cases.

Automation with Macros

UVM provides field automation macros to avoid manually implementing do_copy(), do_compare(), etc. 

class my_item extends uvm_sequence_item;

  rand bit [7:0] addr;
  rand bit [31:0] data;

  `uvm_object_utils_begin(my_item)
    `uvm_field_int(addr, UVM_ALL_ON)
    `uvm_field_int(data, UVM_ALL_ON)
  `uvm_object_utils_end

  function new(string name = "my_item");
    super.new(name);
  endfunction

endclass
These macros automatically implement:
  • Factory registration
  • Print
  • Copy
  • Compare
  • Pack / Unpack

uvm_object vs uvm_component

Feature uvm_object uvm_component
Hierarchy No Yes
Phases No Yes
Factory Support Yes Yes
Used for Data / Transactions Structural elements (env, agent, driver)

Expert Insight

As a verification engineer, mastering uvm_object is critical. Scoreboards, sequences, RAL models, and predictors all rely heavily on it. If you understand how do_copy(), do_compare(), and factory registration work internally, you are no longer a beginner in UVM.