. It is extended from its parent class uvm_resource_dbMarch 24, 2021. uvm_object is basically the main class. Hence, it is required to have proper synchronization to avoid objects/components being called before they are created, The UVM phasing mechanism serves the purpose of synchronization. Deploying Parameterized Interface with UVM Wayne Yun AMD, Inc. What is a UVM Object? On the other hand, UVM objects are transient. events. logger. On calling `uvm_do () the above-defined 6 steps will be executed. They allow access to the functions copy, compare, pack, unpack, record. If you haven't included the file "monitor. Factory is a centralized location to make calls from look-up tables for creation of any transaction types. We have seen put and get methods to operate with only one outstanding transaction at a time i. trigger. That's it. // Create a new class with a single member called // count that stores integer values class Packet; int count; endclass module tb; // Create two "handles" for the class Packet // Note: These "handles" now. 2-2020 standard. Classes derived from uvm_object must implement the pure virtual methods such as create. You're trying to assign a handle of base class type to a handle of derived class type, which isn't allowed in SV. uvm config db set method void uvm_config_db#(type T = int)::set(uvm_component cntxt, string inst_name, string field_name, T value); Where, T is the type of element being configured. 1 to create reusable and portable testbenches. reg. 2. if you just declare the P2 as" My_Packet P2;" , the cast will work. UVM is based on Open Verification Methodology (OVM) and Verification Methodology Manual (VVM). UVM 1. This locking mechanism is implemented using lock and grab methods. A UVM sequence is just a SystemVerilog object that is constructed by calling new. . 2 uvm_object constructor. This method calls uvm_event_base::wait_trigger followed by get_trigger_data. Then you can do: typedef uvm_object_registry# (abc_test_seq,`STR (`SEQ_NAME (abc))) type_id;. T he run_phase is implemented as a forever begin-end loop. It does a deep comparison. Share. It allows for generic containers of objects to be created, similar to a void pointer in the C programming language. 613. event_object event_object_h; uvm_object temp_obj; . Refer to “Macros” in the UVM 1. uvm_test extends from uvm_component which extends from uvm_object. `uvm_field_intとは. The UVM is completely described in the IEEE 1800. The set_type_override() is another static function of the uvm_object_registry. The handle to the uvm_resource object is stored in two kinds of uvm_queues. Follow. uvm_component_param_utils uvm_object_param_utils. An appropriate `uvm_field_* macro is required to use based on the data type of class properties. Factory is a singleton object and there is only one instance of the factory in a UVM environment. Field definition remains the same as print_field method. I guess the name "automation" is used, because they automatically write code so you don't have to. 1 class-based verification library and reuse methodology for SystemVerilog. We would like to show you a description here but the site won’t allow us. Let’s call the record in our jelly bean scoreboard. g. uvm_object is the main class in which common functions to print, copy, and compare two objects of the same class are defined. The size variable indicates the number of bits. 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. Two things: 1) You could extend mem_seq_item from "uvm_sequence_item" instead of "uvm_object". They are distinct objects. This article explains how to use a verbosity threshold to filter messages. That means the other parameter Tname of. The UVM object is a data structure used for testbench configuration and it is the base class available for component and sequence branch. Must define a pool before use: typedef uvm_pool(. The difference between a UVM Object and a UVM Component is that UVM components are non-transient, meaning they have a static nature. Abstract- SystemVerilog provides several mechanisms for layering constraints in an object. class my_test extends uvm_test uvm_table_printer m_printer; //. It also becomes easier to connect to design regardless of the number of ports it has since that information is encapsulated in an interface. UVM_WARNING @ 0: reporter [TPRGED] Type name 'packet2mem_comp_Str' already registered with factory. 1 (IEEE 1800. The uvm_object or sequence overriding is similar to the uvm_component overriding factory mechanism that returns the derived object handle using a base class handle. myagent. Classes derived from uvm_object must implement the pure virtual methods such as create. Inline constraints (i. sv" into the same package you probably need to import the package where monitor. S. This is particularly useful when dealing with serial forms of communication like SPI, I 2 C and RS-232. Thanks,Hello lets say I have a code like this, the parameters NUM_MASTERS and NUM_SLAVES are defined in configuration object: class abc extends uvm_scoreboard; configuration cfg; wrapper_class master[];. It works with uvm_object and interface. Let’s implement the callback in uvm_sequence to modify the sequence_item before sending it to the driver. : bit get(uvm_component cntxt, string inst_name, string field_name, inout T. Here is my thought/search process: I've found that uvm_factory class has a register method which registers a proxy object of a given type. UVM components support logging with the following steps. Writing Verilog test benches is always fun after completing RTL Design. do_pack. 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. UVM_DEFAULT specifies. Share. 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. I can't use a generate loop inside the class and I couldn't find out a way to use a for loop to pass the individual parameters. 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. Note that all the functions are static and must be called using the :: scope operator. Inside a uvm_env class, I try to create an array of another uvm_env class. Create and register the callback object. You can use the uvm_object_registry (T,S) or uvm_component_registry (T,S) registration macros. We would like to show you a description here but the site won’t allow us. raise_objection (uvm_object obj = null, string description = ” “, int count = 1) Raises number of objections for corresponding object with default count = 1. UVMFactory is used to create objects of type UVMComponent and UVMObject (and their derived user-defined types). UVM has a rich reporting facility. uvm_pool and semaphore 101. A uvm_queue is created for every unique field_name. `uvm_do (Item/Seq) This macro takes seq_item or sequence as argument. UVM pre-defines six verbosity levels; UVM_NONE to UVM_DEBUG. Its intention is to print the name of the type of a given object instance. First we’ll handle blocking operations. Don’t confuse the class variable and the object. 2 User’s Guide. We would like to show you a description here but the site won’t allow us. To implement some important methods in classes and variables, UVM provides the UVM Macros. 02. Unfortunately this wont work yet because we have to register seq_item as follows `uvm_object_param_utils(seq_item#(A)). To access a DUT signal in a UVM component or UVM object, you can use the UVM Register Abstraction Layer (RAL) to create a register model of the DUT’s design. UVM pre-defines six verbosity levels; UVM_NONE to UVM_DEBUG. set_type_override_by_name ("base_sequence",`STR (`SEQ_NAME (abc))); In. It allows for generic containers of objects to be created, similar to a void pointer in the C programming language. The UVM 1. 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. Both UVM Factories allow you to create objects, either the base type or a derived, without changing the call to create(). For Design specification and Verification plan, refer to Memory Model. 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. Does an abstract class (virtual class. The uvm_object class is the base class for all UVM data and hierarchical classes. `uvm_object_param_utils_begin. uvm_reg::update. uvm_component provide a set of convenience functions that call the uvm_factory member functions with a simplified interface. wait_trigger_data. SNUG 2018 Page 6 SystemVerilog Virtual Classes, Methods, Interfaces Rev 1. pyuvm is the Universal Verification Methodology implemented in Python instead of SystemVerilog. {"payload":{"allShortcutsEnabled":false,"fileTree":{"distrib/src/reg":{"items":[{"name":"sequences","path":"distrib/src/reg/sequences","contentType":"directory. Every class item derived from uvm_object will have a printer instance within it. UVM configuration provides. “value” is the actual object handle shared through the uvm_config_db. 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. H. The usage of Factory involves three steps. e. Subtypes of uvm_printer implement different print formats, or policies. Let’s look at how we. uvm event callbacks are an alternative to using processes that wait on events. 2 Class Reference represents the foundation used to create the UVM 1. Testbench diagram. 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. Typically configuration classes and data objects are derived from. Factory is a singleton object and there is only one instance of the factory in a UVM environment. That means the default value is going to be used in new(). Every class item derived from uvm_object will have a printer instance within it. 2? I tried the following, which looked like it may work. The constructor of uvm_component adds a uvm_component parent argument which is used to create. UVM objects are. All the signals listed as the module ports belong to APB specification. `uvm_field_utils_begin. 1 Answer. A block represents a design hierarchy. uvm_event is used to synchronize the two processes. This keeps your code base stable,. Intro. sv & uvm_pkg. You can also use get_id(), get_message() etc. You need to create a uvm_object temp variable, then do an explicit dynamic cast, e. A flat uvm_config_db with wildcard scopes and many entries can be a performance hog. Bases: object. 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. g. *,_ALL_,UVM_DEBUG,run I want to leave the entire testbench verbosity as sv_medium, except for one object of the following class. Building UVM Verification Environment from Scratch. UVM REPORTING The uvm_report_object provides an interface to the UVM reporting facility. The specialized class type_id gives us access to all the static declarations inside ovm_object_registry. def compare_field (self, name, lhs, rhs, size, radix = UVM_NORADIX): """ Function: compare_field Compares two integral values. An uvm_component inherits from. Inside uvm_component_registry class there is a get method, which. raise_objection()을 호출하면 uvm_object 클래스의 카운트가 증가해서 0 값이 아닌 다른 값을 가지게 되고 그러면 uvm_phase의 phase executer가 시뮬레이션을 종료하지 않게 됩니다. It performs a deep copy. PyUVM Description. There is often a need to copy, compare and print values in these classes. So all you need to do is remove the type E parameter declaration. Such a configuration database allows us to store different configuration settings under different names. This object must be factory-enabled. Using Callback. 02. UVM_Object: uvm_object is basically the main class. Eventually, everything in UVM is derived from this base class, including uvm_sequence_item. uvm_factory. The UVM factory knows which component to create even if the component type is overridden. Use uvm_config_db# (uvm_object)::set. 02. sv is included. print_topology() or factory. uvm_object クラスはアブストラクト・クラスである為、uvm_object のインスタンスを作る事は出 来ません。但し、uvm_object クラスのハンドルを定義する事は可能です。例えば、メソッドの引 数として generic なハンドルを宣言する為に使用する事. The uvm_resource#(type T) is a parameterized class that provides additional functions like read() and write() for resource operation. The uvm_heartbeat class is derived from uvm_object and it is associated with a specific objection object. Interfaces can contain tasks, functions, parameters, variables, functional coverage, and assertions. Both the main sequence and the other sequence get an uvm_event with. The uvm_event class is directly derived from the uvm_object class. By applying stimulus to the register model, the actual design registers will exhibit the changes applied by the stimulus. Phases : UVM defines a set of simulation phases that enable users to control the order in which testbench components are created, initialized, and executed. 1에서는 uvm_object에 대한 constructor가 필수 사항이 아니었지만, UVM 1. Through this interface, components issue the various messages with different severity levels that occur during simulation. It is intended for verification engineers who want to use UVM 1. This method calls uvm_event_base::wait_ptrigger followed by. Interfaces can contain tasks, functions, parameters, variables, functional coverage, and assertions. Abstract- SystemVerilog provides several mechanisms for layering constraints in an object. Gets the data, if any, provided by the last call to trigger. Improve this answer. 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. As I understood for all items inherited from uvm_component, they all need uvm_component parent as part of constructor input argument. The update can be performed using the using the physical interfaces (frontdoor) or uvm_reg::poke () (backdoor) access. 05 Data Arrays 01. UVMFactory [source] ¶. UVM provides a transaction class that can be extended to create transaction objects that carry information between the DUT and the testbench. User classes derived directly from uvm_void inherit none of the UVM functionality, but. uvm_object::new says that m_inst_id == m_inst_count++. OOP design patterns take reuse another step. 04 Packed and Unpacked arrays 01. TimConclusion. UVMObject (name: str) [source] ¶ Bases: sv_obj. “virtual” keyword is common in all of them. uvm_objects have clone/do_copy virtual methods, that can be used to clone/ do a deep copy of an object. ), which extends from uvm_object, benefit from using uvm utility macros (`uvm_component_utils, `uvm_object_utils)? As I understand, `uvm_component_utils and `uvm_object_utils are used to register a class w/ the factory so objects of that class can be over. This class provides base functionality for both user-defined RegModel test sequences and “register translation sequences”. A cleaner way would be to use the sequence library provided by UVM as uvm_sequence_library. When a callback is attached to an event, the attached callback function/s is called each time the event is triggered. 1 Answer. 05 Data Arrays 01. The driver receives the item and drives it to the DUT through a virtual interface. uvm_config_db#(TYPE)::set(this,"*. Accellera believes standards are an important ingredient to foster innovation and continues to encourage industry innovation based on its standards. 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. Abstract- SystemVerilog provides several mechanisms for layering constraints in an object. You need to create an array of ral_block_traffic_cfg objects: rand ral_block_traffic_cfg cfg [2]; You created an array of type uvm_reg_block, named it ral_cfg, but it has nothing to do with the ral_block_traffic_cfg object. pyuvm is the Universal Verification Methodology implemented in Python instead of SystemVerilog. 1 features from the base classes to the. UVM TestBench to verify Memory Model. The uvm_void class is the base class for all UVM classes. ), instance identification fields (name, type name, unique id, etc. 在使用UVM 寄存器的时候，本质是将high_level的uvm_reg_transaction (也叫uvm_reg_item)转换成物理的transaction (物理dirver所使用的transaction,用户定义的BUS_transaction),转换过程是. Object Overriding; UVM Phases; UVM Objections; UVM Object. Blocks ¶. Yes, the UVM create() method calls new() constructor on the object without any arguments (string name is not passed in there). The UVM heartbeat can detect simulation hang or lock-up conditions at an early stage rather than the expiry of the global simulation timeout. Factory is a singleton object and there is only one instance of the factory in a UVM environment. The UVM sequencer provides the facility to have exclusive access for the sequence to a driver via a sequencer using a locking mechanism. ; Once you convert your testbench from passing individual values to passing config objects, you can see the bigger picture, which is that a testbench is configured and built from the top down, guided by the configuration. . 1 class-based verification library and reuse methodology for SystemVerilog. The UVM TLM library defines several abstract, transaction-level interfaces and the ports and exports that facilitate their use. 1 min read. 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. It is an abstract class with no data members or functions. uvm_object has both as seen in its constructor. In our case, two uvm_queues are created; one for the "jb_if1" and the other for the "jb_if2". drop_objection (uvm_object obj = null, string description = ” “, int count = 1) Drops number of objections for corresponding object with default count = 1 The copy method does a copy of the mentioned object. uvm_reg_sequence. 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. The uvm_object_registry has static methods, which you call with the class::type_id::create () syntax. uvm_object-based class declarations may contain one of the above forms of utility macros. to drive the designated signals into DUT. A flat uvm_config_db with wildcard scopes and many entries can be a performance hog. For more efficient and more flexible implementation, we can use user definable do_*() hooks. Description. I have two class handles inside my sequence item. Blocking operationsPacking is just a way to convert your uvm_object into a bit array. It has various methods to create different uvm_component or uvm_object instances and also to override it. 2. 1. However, are they supported by UVM?When working with UVM, the phrase "you gotta use the factory!" gets drilled into our heads constantly. The clone () method was declared in uvm_object and returns a handle of type uvm_object. event_object event_object_h; uvm_object temp_obj; . base. The first three methods above take uvm_object_wrapper as their type argument (s). A scope is a context like an instantiation of the component in the uvm. On calling `uvm_do () the above-defined 6 steps will be executed. Create a custom class inherited from uvm_env, register with factory, and call new. ”. A resource is any piece of information that is shared between more than one component or object. You can think of any method call as having an implicit this argument. UVM also introduces a bunch of automation mechanisms for implementing print, copy, and compare objects and are defined using the field macros. 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. You're trying to assign a handle of base class type to a handle of derived class type, which isn't allowed in SV. get_trigger_data. Posted November 30, 2015. This improves flexibility and scalability of testbench. TYPE’s constructor, if defined, must have default values on all it arguments. task body; i2c_packet pkt; pkt = i2c_packet::type_id::create("pkt"); pkt. 4) uvm_object required to define the uvm_object::creat() method. We would like to show you a description here but the site won’t allow us. __init__() if you override the __init__() method in a uvm_component. 2-2017. svh" endpackage. The UVM application programming interface (API) defines a standard for the creation, integration, and extension of UVM Verification Components (UVCs) and verification environments that scale from block to system. The UVM agent is a hierarchical component that groups together other verification components that are dealing with a specific DUT interface. A policy class to allow pairs of transactions to be handled as a single uvm_object type. Read more: UVM Object [uvm_object] In my last post, I recommended that you give every SystemVerilog object either a unique ID or name. 1. Static components & Dynamic components. uvm_config_db is a parameterized class that is parameterized with the data type of object that is being set or get. Steps involved are, Write callback class. uvm_config_dbに渡すパラメータタイプはuvm_object_wrapperになります。これはuvm_config_dbにtypeを登録する場合の型です。 第一引数は通常はthisです。 第二引数は対象となるシーケンサのUVMの階層名+フェーズ名になります。From the application point of view, UVM Factory facilitates an object of one type to be substituted with an object of derived type without having to change the structure of the Testbench or modify the Testbench code. This class will also need to be able to get information from the config_db using hierarchical paths, and plain old uvm_objects don't have hierarchy. The compare method returns 1 if comparison matches for the current object when it is compared with the R. UVM TestBench to verify Memory Model. In the declaration of class A, one can invoke the `uvm_object_utils (A) or `uvm_component_utils (A) registration macros. the reason for this is that for IUS the m_inst_id is being set to the. This is known as the UVM factory override mechanism. uvm_component provide a set of convenience functions that call the uvm_factory member functions with a simplified interface. Using start_item/finish_item methods. As the name suggests, it keeps a track of the sequences that are registered with it, and calls them a number of times in a random fashion. A policy object can be passed along to set parameters like depth of comparison, verbosity, maximum number of. Classes deriving from UVMObject must implement methods such as create and get_type_name. answered Apr 21, 2014 at 0:28. Inline constraints (i. Pack. Teams. As name indicates, Dynamic components are generated, perform their tasks and their life span is finished at the end of a simulation cycle. typedef uvm_object_string_pool #(uvm_event #(uvm_object)) uvm_event_pool; We’ll go in detail of uvm_pool in another post. You should be compiling classes into a package. This enables us to monitor and record the transactions via the interface within this block. Include the class inside the testbench and instantiate an object. For this purpose, the factory needs to know all the types of classes created within the testbench by a process called as registration. ”. 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. To avoid the overhead of creating an instance of every component and object that get registered, the factory holds lightweight wrappers, or proxies. The driver receives the item and drives it to the DUT through a virtual interface. 02 SystemVerilog 기초 1 01. This means that all uvm_components are report objects, which is why you must call super(). TLM Communication. By knowledge I mean uvm_component is set up to link parents with children as a database that can be traversed via a named hierarchy. build_phase (phase) must be called in the. Here are my codes: typedef class tmp_for_test; class config_agent extends uvm_agent; typedef config_agent this_type; tmp_for_test #(int, byte) tmp_f_t; // Provide implmentations of virtual me. There are different variations to this macro, just like `uvm_do_*. factory. uvm_resource_pool rp = uvm_resource_pool::get(); uvm_resource#(T) _type = new(); uvm_queue#(uvm_resource_base) q; q =. Extend that class and implement the virtual method. uvm_object like uvm_transaction is not connected to any particular DUT interface and its fields can take any random value based on randomization constraints. OOP enables writing reusable code. That means the other parameter Tname of. Improve this answer. Place the callback hook. Similarly uvm_object::compare() calls the __m_uvm_field_automation() with UVM_COMPARE. There are two branches in the hierarchy : Under uvm_component: Classes that define verification components like driver, monitor and. 3. The uvm_analysis_port is a specialized TLM based class whose interface consists of a single function write () and can be embedded within any component as shown in the snippet below. The factory infrastructure is responsible forWe would like to show you a description here but the site won’t allow us. Share. These loggers are part of the cocotb logging system. The uvm_config_db class provides a convenience interface on top of the uvm_resource_db to simplify the basic interface used for uvm_component instances. The first kind of queues store the handles to the uvm_resource objects that have the common field_name. In order to create a user-defined sequence : Derive from uvm_sequence base class with a specified data object type. The first kind of queues store the handles to the uvm_resource objects that have the common field_name. uvm_component provide a set of convenience functions that call the uvm_factory member functions with a simplified interface. get_type_name isn't intended to print the name of a type. First, let's. Line 11-Line 15 Use the UVM functions to automatically implement functions such as copy(), compare(), print(), pack(), and so on. These macros are used to start sequences and sequence items on default sequencer, m_sequencer. UVM TestBench architecture. Inline constraints (i. These macros can appear anywhere in the declaration space of the class declaration of T and will associate the string S to the object type T. Once unzipped, I see the source files with uvm. System Verilog has virtual methods, virtual interfaces, and virtual classes. In other words, uvm_objects are transient, such as transactions that are created when needed and disappear when not used anymore. The uvm_object class is the base class for all UVM data and hierarchical classes. We would like to show you a description here but the site won’t allow us. The factory is a special class in UVM that creates an instance for you of whatever uvm_object or uvm_component type you specify. uvm_env is extended from uvm_component and does not contain any extra functionality. 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. This section defines the proxy component and object classes used by the factory. That means the default value is going to be used in new(). A block has one or more address maps, each corresponding to a physical. The UVM methodology enables engineers to quickly develop powerful,. Policy classes are used to implement polymorphic operations that differ between built-in types and class-based types. A memory is a collection of contiguous locations. 03 Operators 01. print(); Use the uvm_object_utils and uvm_field_* macros in your uvm_sequence_item class to control what gets printed. Add a comment. 02. Share. 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. Also, uvm_pool is a singleton class , that explains why it has global access. Implement the function "create()" `define m_uvm_object_create_func(T) function uvm_object create (string name=""); T tmp; `ifdef. For convenience, you can use the subtype, uvm_in_order_built_in_comparator # (T) for built-in types. Jun 20, 2014 at 15:13. Implementations of uvm_object::do_pack and uvm_object::do_unpack should regard this bit when performing their respective operation. 1. Then you can do: typedef uvm_object_registry# (abc_test_seq,`STR (`SEQ_NAME (abc))) type_id;. The uvm_object provides methods like create, clone, copy, record, compare, print, etc. But, virtual_sequence and virtual_sequencer do not require any virtual keyword. 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). 1. argument object. 1. 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. After the utility macro are the field automation macros in the form ‘uvm_field_*(data member, flag). uvm_sequence_item class hierarchy As shown in the above diagram, uvm_sequence_item is derived from the uvm_transaction class. We would like to show you a description here but the site won’t allow us. This class will also need to be able to get information from the config_db using hierarchical paths, and plain old uvm_objects don't have hierarchy. trigger. The first kind of queues store the handles to the uvm_resource objects that have the common field_name. User classes derived directly from uvm_void inherit none of the UVM functionality, but such classes may be placed.