print_topology() or factory. SNUG 2012 6 The OVM/UVM Factory & Factory OverridesThe UVM register layer acts similarly by modeling and abstracting registers of a design. The name of an uvm_event is unique, you can use uvm_event_pool to get the instance of the uvm_event with the same name. Overriding a type involves the following steps: Firstly, the. 02 Data Types 01. In a previous article, print, do_print and use of automation macros to print were discussed. The uvm_object class is the base class for all UVM data and hierarchical classes. The UVM factory allows an object of one type to be overridden with an object of its derived type without changing the testbench structure. The utility macros help to register each object with the factory. It seems to me that the monitor class is missing from the scope of the soc_uvm_env in other words during compilation of soc_uvm. After the utility macro are the field automation macros in the form ‘uvm_field_*(data member, flag). The create method internally makes a call to the factory to look up the requested type and then. TimConclusion. `uvm_object_param_utils(TYPE) For parameterized objects, with field macros, use `uvm_object_param_utils_begin(TYPE) `uvm_field_* macro invocations here `uvm_object_utils_end Simple (non-parameterized) objects use the uvm_object_utils* versions, which do the following: Implements get_type_name, which returns TYPE as a. 0 using simple producer/consumer examples. 02 Data Types 01. Every class item derived from uvm_object will have a printer instance within it. The record function takes a recording policy object as the argument (line 14). Unfortunately, SystemVerilog does not provide a good way to save Creates a new event object. In our case, two uvm_queues are created; one for the "jb_if1" and the other for the "jb_if2". Aside from registering a class with the factory, we've seen that the. object queues and publishes a number of transfers equal to the total length of the burst size. This is not a complete design since our purpose is simply to show how registers in this design can be read/written using a UVM register model. g. UVMObject. For example, a uvm_registry base class could have provided the required infrastructure for creation and factory overrides. Overall Implementation To link the RAL with the configuration object, we initialize the registers in every configuration object as handlesThe callback pool is a singleton object that can be accessed by calling uvm_callbacks#(T)::get_global_pool() or uvm_component::get_callback_pool(), where T is the type of the UVM class or component. uvm_object has many common functions like print, copy and compare that are available to all its child classes and can be used out of the box if UVM automation macros are used inside the class definition. Previous Article. Better yet, don't use any field macros at all as they are horribly inefficient. We have already seen how to use `uvm_do set of macros. UVMReportObject. Refer to “Macros” in the UVM 1. UVM also introduces a bunch of automation mechanisms for implementing print, copy, and compare objects and are defined using the field macros. Here are the general steps to create and use a register. This port contains a list of analysis exports that are connected to it. One thing that always confuses me: is whether add uvm_component parent in the class constructor of UVM objects or not. Conclusion. Unlike registers, memories are not mirrored because of the potentially large data space: tests that walk the entire memory space would negate any benefit from sparse memory modelling techniques. The create () method essentially just calls uvm_factory::create_object_by_type (). factory. 1-289-695-1969 shihua. raise_objection (uvm_object obj = null, string description = ” “, int count = 1) Raises number of objections for corresponding object with default count = 1. Both the main sequence and the other sequence get an uvm_event with. Say the object is "my_tb". 1 Class Reference is a comprehensive document that describes the classes, methods, macros, and callbacks that constitute the UVM 1. There are many kinds of design patterns. Similarly, SystemVerilog casting means the conversion of one data type to another datatype. The uvm_object_registry serves as a lightweight proxy for a uvm_object of type T and type name Tname, a string. is just the same as the previous two, you need to use them when your uvm_object or uvm_component has parameters. A flat uvm_config_db with wildcard scopes and many entries can be a performance hog. uvm_resource_pool rp = uvm_resource_pool::get(); uvm_resource#(T) _type = new(); uvm_queue#(uvm_resource_base) q; q =. The UVM 1. In the declaration of class A, one can invoke the `uvm_object_utils (A) or `uvm_component_utils (A) registration macros. This method calls uvm_event_base::wait_ptrigger followed by. I have two class handles inside my sequence item. It does a deep comparison. This is applicable for uvm objects and components. FollowSimple (non-parameterized) objects use the uvm_object_utils* versions, which do the following: Implements get_type_name, which returns TYPE as a string; Implements create, which allocates an object of type TYPE by calling its constructor with no arguments. Improve this answer. wait_trigger_data. A uvm_queue is created for every unique field_name. uvm_component provide a set of convenience functions that call the uvm_factory member functions with a simplified interface. Then you can do: typedef uvm_object_registry# (abc_test_seq,`STR (`SEQ_NAME (abc))) type_id;. The handle to the uvm_resource object is stored in two kinds of uvm_queues. svh" `include "packet_sequencer. The do_pack() method is called by the pack(), pack_bytes(), and pack_ints() methods. 1 min read. 02. A utils macro should be used inside every user-defined class that extends uvm_object directly or indirectly, including uvm_sequence_item and uvm_component. Even the uvm_object_registry and uvm_component_registry classes contain a lot of duplicated code that could have been refactored. Sorted by: 1. The run_phase is a thread started automatically by the UVM core. Classes deriving from uvm_object must implement the pure virtual methods such as create and get_type_name. The UVM class library provides the basic building blocks for creating verification data and components. A grandparent class of uvm_sequence_item is uvm_transaction, which contains the following field definitions: class uvm_transaction extends uvm_object; const uvm_event_pool events = new; uvm_event begin_event; uvm_event end_event; //. wait_ptrigger_data. The configuration object also allows for a higher-level view of the DUTs functions, providing test writers with an abstracted constraint layer not tied to the underlying registers. The primary role of uvm_object class is to define a set of common utility functions like print, copy, compare and record which can be availed by any other class in a UVM testbench to save effort. This applies to all instances of that component type. Accellera UVM Tutorial 2016 is a comprehensive presentation that covers the basics and advanced features of the Universal Verification Methodology (UVM), a standard framework for creating reusable and portable verification components and environments. We would like to show you a description here but the site won’t allow us. In order to understand the different role that the Accellera Portable Test and Stimulus (PSS) standard plays versus UVM, let's consider this brief statement about what PSS is intended to accomplish, taken from the 1. `uvm_create (Item/Seq) This macro creates the item or sequence. uvm_object The primary role of uvm_object class is to define a set of common utility functions like print, copy, compare and record which can be availed by any other class in a UVM testbench to save effort. uvm_object ¶. Here is a transaction class. Object Overriding; UVM Phases; UVM Objections; UVM Object. Test program작성 및 script 작성. Note: The factory override ways are applicable for both uvm components and uvm objects. It consists of all the basic methods, macros, identification fields in it. The uvm_heartbeat class is derived from uvm_object and it is associated with a specific objection object. The following methods are also part of the uvm_objection class: clear(): Immediately clears the objection state. `uvm_do (Item/Seq) This macro takes seq_item or sequence as argument. Deploying Parameterized Interface with UVM Wayne Yun AMD, Inc. Implementations of uvm_object::do_pack and uvm_object::do_unpack should regard this bit when performing their respective operation. In UVM, is there anything in the uvm_object::compare method or uvm_comparer policy to implement a different comparison similar to the VMM compare() kind argument? For example, I would like a mechanism to be able to select between doing a full compare of all object members or a partial subset compare. 02. trigger. typedef uvm_object_string_pool #(uvm_event #(uvm_object)) uvm_event_pool; We’ll go in detail of uvm_pool in another post. class uvm_object; function new (string name); m_inst_id = m_inst_count++; m_leaf_name = name; endfunction endclass. You are mixing up the terms parent and child with the principals of class inheritance. Print method; Copy and clone methods; Compare method; Pack / Unpack methods; Resource database in UVM. class my_driver. This works in conjunction with the Register Adapter, as its bus2reg() function simply grabs the data from the top of its queue and returns its uvm_reg_bus_op object. method_call() is really method_call(. Using do_pack/do_unpack. Objections provide a facility for coordinating status information between two or more participating. UVM uses the concept of a factory where all objects are registered with it so that it can return an object of the requested type when required. The UVM methodology enables engineers to quickly develop powerful,. 1 class-based verification library and reuse methodology for SystemVerilog. The first thing that we need to do is to define a basic callback class in which to specify what functions will be called back. H. randomize with {…} or `uvm_do_with) permit specifying additional constraints when randomizing an object. Inline constraints (i. The first step is to use macros to register all the class types with the factory. PyUVM Description. Code compiled in one compilation unit is not visible to another compilation unit. `uvm_field_intとは. We would like to show you a description here but the site won’t allow us. So UVM phases act as a synchronizing mechanism in the life cycle of a simulation. There are many kinds of design patterns. `uvm_do (Item/Seq) This macro takes seq_item or sequence as argument. OOP design patterns take reuse another step. Similarly, in the second line, the all to the "uvm_root" static get method returns a reference to the top-level "uvm_root" object and we are calling the "set_timeout" method on that object. After new'ing , it uses set_name() to assign the appropriate value to the name string. If you are using OVM/UVM then get_full_name() / get_name() will return the name of the component in the testbench hierarchy. UVM TestBench architecture. Description. Classes derived from uvm_object must implement the pure virtual methods such as create. Using start_item/finish_item methods. Create and register the callback object. reg. Tudor Timi Tudor Timi. macro: Can be used, but try to avoid if you are. This process is shown in the code below:Based on command line arguments like +link_speed and +lanes, a same set of test sequences can be run with all possible configurations. To maintain uniformity in naming the components/objects, all the component/object name’s are starts with mem_ *. uvm_test extends from uvm_component which extends from uvm_object. Block abstraction base class. Inside uvm_component_registry class there is a get method, which. 03 Basic UVM Testbench 작성. 1에서는 uvm_object에 대한 constructor가 필수 사항이 아니었지만, UVM 1. If the processes to trigger and wait for a trigger of an event are running in different components then it is required to share the event handle across the components. UVM utility & field macros. This method calls uvm_event_base::wait_ptrigger followed by. The uvm_comparer adds up policy for the comparison and counts the number of miscompares if any. 2 Class Reference for information on the. Blocking operationsPacking is just a way to convert your uvm_object into a bit array. Construct a Tx object using the handle t1 and give it the ID 42. Read more: UVM Object [uvm_object] In my last post, I recommended that you give every SystemVerilog object either a unique ID or name. This is applicable for uvm objects and components. virtual class uvm_component extends uvm_report_object; uvm_component class definition provides many functions and tasks that are used to find, build, connect, and configure. by extending the uvm_object or the uvm_sequence_item base class. Steps involved are, Write callback class. Triggers the event, resuming all waiting processes. Each resource has a set of scope. UVMには、さまざまなオートメーション機能が実装さ. Abstract- SystemVerilog provides several mechanisms for layering constraints in an object. SystemVerilog Parameterized Classes. Policy classes are used to implement polymorphic operations that differ between built-in types and class-based types. sv and the many svh files for the class files (reg, tlm, macros, drivers. base. UVM tutorial for beginners Introduction Introduction to UVM UVM TestBench TestBecnh Hierarchy and BlockDiagram UVM Sequence item Utility & Field Macros Methods with example Create Print Copy Clone Compare Pack UnPack UVM Sequence Sequence Methods Sequence Macros Sequence Example codes UVM Sequence control UVM. Without it, registration would require an instance of the object itself. as you can see from your log that isnt the case for IUS. On the other side, Static component are physical components which are present since the begining and. The __m_uvm_field_automation() is then used in uvm_object class. This command is going to call the ::type_id::create command from the tb_driver, which happens to be code largely inherited from other macros and classes. com Welcome to our site! EDAboard. Let’s implement the callback in uvm_sequence to modify the sequence_item before sending it to the driver. A user-defined printer has been developed by us. Alternatively, if the change is intended to be global, there is a default printer that automatically created at root called uvm_default_printer . The recommended method in UVM for creating components or transaction objects is to use the built-in method::type_id::create () instead of calling the constructor new () directly. Simple (non-parameterized) objects use the uvm_object_utils* versions, which do the following: Implements get_type_name, which returns TYPE as a string; Implements create, which allocates an object of type TYPE by calling its constructor with no arguments. The factory (or to be precise, uvm_component_registry) will call new on behalf of you. class uvm_object; virtual function uvm_object clone ();. The create() method essentially just calls uvm_factory::create_object_by_type(). It looks like you have a compilation of uvm_pkg from a previous run that is conflicting with this run. 02 SystemVerilog 기초 1 01. The verification testbench will be developed in UVM and has the following block diagram: The sequence generates a random stream of input values that will be passed to the driver as a uvm_sequence_item. The uvm_object class is the base class for all UVM data and hierarchical classes. All other class variables virtual function void. We’ll examine pyuvm’s implementation TLM 1. 1 Answer. The compare method returns 1 if comparison matches for the current object when it is compared with the R. It helps increase flexibility and resuability of our testbench. 2 User’s Guide. 1 library. Description. Using do_copy. UVMRegBlock(name='', has_coverage=0) [source] ¶. Then from your component, do. dave_59. gz. That is the macro call is delegated to a uvm_report_error() function call. Factory is a singleton object and there is only one instance of the factory in a UVM environment. Users can configure what actions are taken and what file(s) are output for individual messages from a particular component or for all. Implementations of uvm_object::do_pack and uvm_object::do_unpack should regard this bit when performing their respective operation. You always could use 'uvm_field_array_int and a pair of pack/unpack function that transforms the pixel info into an int (you would still have a byte of the int free) and the other way round. User classes derived directly from uvm_void inherit none of the UVM functionality, but such classes may be. module traffic ( input pclk, input presetn, input [31:0] paddr, input [31:0] pwdata. com Each component goes through a pre-defined set of phases, and it cannot proceed to the next phase until all components finish their execution in the current phase. This doesn't have any purpose, but serves as the base class for all UVM classes. The concept of design patterns specifically for SystemVerilog object oriented programming (OOP) languages was popularized in 1994 by the book “Design Patterns: Elements of Reusable Object-Oriented Software. uvm_event is used to synchronize the two processes. Since the RTL code does not know anything about the test class, it uses a null handle, and “uvm_test_top“, the instance name of the test object. The print method is used to deep print UVM object class properties in a well-formatted manner. Enjoy your verification journey!SystemVerilog functions have the same characteristics as the ones in Verilog. 01 SystemVerilog Testbench 구조 01. `uvm_object_param_utils. It also becomes easier to connect to design regardless of the number of ports it has since that information is encapsulated in an interface. event_object_h =. The user can simply apply a different. First we’ll handle blocking operations. Fundamentals of SystemVerilog Testbench Environment. Policy classes are used to implement polymorphic operations that differ between built-in types and class-based types. Writing Verilog test benches is always fun after completing RTL Design. event_object event_object_h; uvm_object temp_obj; . Note that all the functions are static and must be called using the :: scope operator. wait_trigger_data. The uvm_void class is the base class for all UVM classes. The uvm_object_registry serves as a lightweight proxy for a uvm_object of type T and type name Tname, a string. g. Before moving to uvm_sequence_item will look into uvm_object concepts required to write uvm_sequence_item, The uvm_object has a number of virtual methods that are used to implement common data object functions (copy, clone, compare, print, transaction, and recording) and these should be implemented to make the sequence_item more general purpose. This guide is a way to apply the UVM 1. – dave_59. It is an abstract class with no data members or functions. These macros form a block in which `uvm_field_* macros can be placed. UVM automation macros also include mechanisms to pack class variables into a bit or byte stream, and unpack a bit stream and populate the class contents. If we already have a data object that we simply want to send to a sequencer, we can use `uvm_send. You need to create a uvm_object temp variable, then do an explicit dynamic cast, e. UVM provides a transaction class that can be extended to create transaction objects that carry information between the DUT and the testbench. Pre-defined Verbosity Levels. Multiple recipients accessing an object via get(), will access the same object. Second, super. event_object_h =. `uvm_object_utils. It can be constructed from many different places, but normally a test might construct sequences and then run them – they embody the test. answered Jun 19, 2014 at 23:32. To maintain uniformity in naming the components/objects, all the component/object name’s are starts with mem_ *. pyuvm uses cocotb to interact with the simulator and schedule simulation events. There are four basic reporting functions that can be used with different verbosity levels. This is known as the UVM factory override mechanism. ” ) Prints an object and it is recursed depending on depth knob setting. Unfortunately this wont work yet because we have to register seq_item as follows `uvm_object_param_utils(seq_item#(A)). by The Art of Verification. // my_env is user-given name for this class that has been derived from "uvm_env" class my_env extends uvm_env; // [Recommended] Makes this driver more re-usable `uvm_component_utils (my_env) // This is standard code for all. These macros are used to start sequences and sequence items on default sequencer, m_sequencer. function new (string name, uvm_component parent); super. Parameterized classes in the UVM must be registered using the uvm_object_param_utils macro as below: `uvm_object_param_utils (som_util# (entry_w)) For more background, please see my discussion on this topic. Sorted by: 0. Subtypes of uvm_printer implement different print formats, or policies. The uvm_object class is the base class for all UVM data and hierarchical classes. I've used uvm_queue because there isn't any trivial container object in UVM. As you see the following diagram, the uvm_object::copy() calls the __m_uvm_field_automation() with UVM_COPY as the value of the what__. They are based on uvm component/object type or uvm compoenent/object name. But that's another debate. randomize with {…} or `uvm_do_with) permit specifying additional constraints when randomizing an object. We would like to show you a description here but the site won’t allow us. The uvm_config_db class is the recommended way to access the resource database. 用途は、UVMの「オートメーション」機能を適用するために使います。. pseudo code looks like this: class seq_item extends uvm_sequence_item; rand class_a a; rand class_b b; endclass// seq_item class class_a extends uvm_object; rand bit field_1; rand bit field_2; endclass//class_a class class_b. The documentation only instructs on how to unzip the tar. uvm_component_param_utils uvm_object_param_utils. The first kind of queues store the handles to the uvm_resource objects that have the common field_name. The UVM sequencer provides the facility to have exclusive access for the sequence to a driver via a sequencer using a locking mechanism. Once unzipped, I see the source files with uvm. Within a non-static class method, randomize() and this. 1 Answer. this(this)) and obj. A cleaner implementation would have been for uvm_component_registry to be its own class, that doesn’t extend uvm_object_wrapper, that instead creates an instance of a uvm_object_wrapper and registers it with the factory instead of itself. 2-2020 standard. the uvm_event class makes it easy by providing uvm_event_pool. When the factory is called upon to create an object. In the UVM, there are mechanisms to automate the retrieval of data from the configuration database. 2 User’s Guide. Instances of these lightweight proxies, representing every uvm_object-based and uvm_component-based object available in the test environment, are registered with the uvm_factory. Create uvm_object base class. randomize with {…} or `uvm_do_with) permit specifying additional constraints when randomizing an object. : bit get(uvm_component cntxt, string inst_name, string field_name, inout T. Static components & Dynamic components. 05 Data Arrays 01. Through this interface, components issue the various messages with different severity levels that occur during simulation. Description. Supposed that your component name is "comp" in ENV, and the env is named "env" in the uvm_test, so in test bench top module, you should use below code to get the configuration handle. uvm_object has many common functions like print, copy and compare that are available to all its child classes and can be used out of the box if UVM automation macros are used inside the class definition. 06 Array Operators and Methods. UVM Testbench 작성 00장 둘러보기 00. The uvm_subscriber is derived from uvm_component and adds up the analysis_export port in the class. The proxy enables efficient registration with the uvm_factory. UVMObject (name: str) [source] ¶ Bases: sv_obj. Try these examples yourself. The important thing to remember is that each entry needs a unique field name or label (if the global scope is being used), or the path needs to 1 Answer. Similarly uvm_object::compare() calls the __m_uvm_field_automation() with UVM_COMPARE. Understand the UVM hierarchies and various components needed to build a comprehensive UVM Testbench; Design and implement various testbench components, such as driver, monitor, sequencer, agent, environment, scoreboard, coverage, and environment. it does not have anything rand). SNUG 2018 Page 6 SystemVerilog Virtual Classes, Methods, Interfaces Rev 1. Registration: While defining a class , its type has to be registered with the uvm factory. The monitor captures values on the DUT's input and output pin. g. Line 11-Line 15 Use the UVM functions to automatically implement functions such as copy(), compare(), print(), pack(), and so on. “value” is the actual object handle shared through the uvm_config_db. Let’s look at how we. It is extended from its parent class uvm_resource_dbusing the macro uvm_add_to_seq_lib to add the sequence into the library [`uvm_add_to_seq_lib(rstSeqnc, cfgSeqncLib) ] gives us the feeling that its adding an instance of the sequence into an array present in the sequence library and this instance can be used later in the sequence library. UVM Factory Override. raise_objection (uvm_object obj = null, string description = ” “, int count = 1) Raises number of objections for corresponding object with default count = 1. Parameterized classes in the UVM must be registered using the uvm_object_param_utils macro as below: `uvm_object_param_utils (som_util# (entry_w)) For more background, please see my discussion on this topic. UVM objects are. The UVMObject class is the base class for all UVM data and hierarchical classes. S. But, virtual_sequence and virtual_sequencer do not require any virtual keyword. You can use wildcards in the. That method looks through an array of type overrides to see if you ever called set_type_override () for this class, then calls new () for the base or override class. User classes derived directly from uvm_void inherit none of the UVM functionality, but. 01 Building blocks in SystemVerilog [email protected] to use the UVM configuration facility? Configuration values are set in the uvm_config_db class using the set() method and retrieved using the get() method. my_sequence and reset_sequence are declared like any normal sequence: my_sequence extends uvm_sequence (#transaction); – noobuntu. So, a data class derived from uvm_sequence_item or uvm_component will have access to the print() function as well. That means the default value is going to be used in new(). In the do_print function, we merely list the variables we want to print using the functions of uvm_printer class (lines 3 to 8). UVM Field Macros. OOP enables writing reusable code. sv & uvm_pkg. Unfortunately, SystemVerilog does not provide a good way to saveCreates a new event object. logger. Connect and share knowledge within a single location that is structured and easy to search. A environment class can also be. Built in types (such as ints, bits, logic, and structs) can be compared using the default values for comp_type, convert, and pair_type. uvm_config_db# (rx_agent_cfg)::get (null, "uvm_test_top. However, are they supported by UVM?When working with UVM, the phrase "you gotta use the factory!" gets drilled into our heads constantly. It does a deep comparison. Because this will be created during the run_phase it can't extend uvm_component, and it wouldn't make sense for this class to have phases. UVM components support logging with the following steps. set_type_override_by_name ("base_sequence",`STR (`SEQ_NAME (abc))); In. When someone wants to implement object names, what they'll do is pass a "string name" in the constructor of every object, so when the object is. Not sure how that is going to help. pyuvm is the Universal Verification Methodology implemented in Python instead of SystemVerilog. Classes derived from uvm_object must implement the pure virtual methods such as create. The function that is actually called depends on the context where the macro is used. When a callback is attached to an event, the attached callback function/s is called each time the event is triggered. 2. e. The source of this command can be traced to the following: (1) tb_driver is an extension of uvm_driver, which is an extension of uvm_component, which is a derivative of. Then the UVM test bench utilizes virtual interfaces at dynamic driver, monitor class to access static interfaces [3], it retrieves the bind interface instance handle by reading uvm_resouce_db: Figure 2 – connect RTL and UVM by interface bind uvm_pkg::uvm_resource_db#( virtual svt_axi_slave_if)::read_by_name. So long as the Register Predictor receives a uvm_reg_bus_op object for eachThe TLM FIFO provides storage for the transactions between two independently running processes. print() routines you get what you expect. The UVM heartbeat can detect simulation hang or lock-up conditions at an early stage rather than the expiry of the global simulation timeout. このページの最後に載せておきます。. Accellera believes standards are an important ingredient to foster innovation and continues to encourage industry innovation based on its standards. Length: 4 Days (32 hours) The Universal Verification Methodology (UVM) is the IEEE1800. build_phase (phase) must be called in the. That means the other parameter Tname of. UVM TestBench architecture. The update can be performed using the using the physical interfaces (frontdoor) or uvm_reg::poke () (backdoor) access. The uvm_resource#(type T) is a parameterized class that provides additional functions like read() and write() for resource operation. This class constructor has a string name argument which is used for messaging and debugging. I did not register any class with the same name, unless the parent one which, I suppose, does not present any problem. uvm_object is basically the main class. The UVM factory knows which component to create even if the component type is overridden. The reason when case2 work is that P1 is assigned to P2 as P2 handle, so a cast from P2 to P2 itself is always ok. This enables us to monitor and record the transactions via the interface within this block. For Design specification and Verification plan, refer to Memory Model. A policy object can be passed along to set parameters like depth of comparison, verbosity, maximum number of. Example 1 - Standard new() constructor for UVM components For transactions (data objects), each object is a unit of data with multiple fields, and transactions do not have a parent. 4) uvm_object required to define the uvm_object::creat() method. The scope of the randomize() object is the this argument inside. 1. Posted November 30, 2015. No string-based lookup support for multiple types with the same type name. In create method, we have to construct a new object of configuration class and update all the important fields and return it. Constraints may be added via inheritance in a derived class. The packer determines how the packing. The UVM class library provides the basic building blocks for creating verification data and components.