Posting answers to few System Verilog Questions (Please refer System Verilog Interview Questions for questions) 10> What is the need of virtual interface ? List The Predefined Randomization Methods. Read more: Computer Skills: Definitions and Examples It allows verification component re-use across verification projects. What are difference between SVA and other assertions? How to avoid race round condition between DUT and test bench in SystemVerilog verification? In SystemVerilog all uninitialized object handles have a special value of null, and therefore whether it is holding an object or not can be found out by comparing the object handle to null. Without Using Randomize Method Or Rand,generate An Array Of Unique Values? The package construct of SystemVerilog aims in solving the above issue. But a module can not call a task or function in a program. Write A Clock Generator Without Using Always Block. Question 14. The size of the dynamic array that needs to beRead More In Verilog declaration of data/task/function within modules are specific to the module only. The new[] operator is used to allocate memory for a dynamic array. Each subroutine retains a local copy of the argument. Program block is newly added in SystemVerilog. 13.// How to use them14.import ABC::Color; // Just import Color15.import ABC::*; // Import everything inside the package. Which hardware description language is more flexible? In formal verification, all cases (inputs and state) are covered implicitly by the tool without the need forRead More Question 10. What Is The Difference Between Byte And Bit [7:0]? 04.// Example void function05.function void my_xor;06.input a; // b and c are hidden input here07.x = a ^ b ^ c;08.endfunction : my_xor09. The data member value can be read with a type that is consistent with current tag value, making it impossible to write one type and read another type of value in tagged union. task pass(int i) // task pass(var int i) pass by reference {delay(10);i = 1;printf(” i is changed to %d at %dn”,i,get_time(LO) );delay(10);i = 2;printf(” i is changed to %d at %dn”,i,get_time(LO) );}, Universal Verification Methodology (UVM) Interview Questions. Scope resolution operator ( :: ) links method declaration to class declaration. Question 22. Modports are used for specifing the direction of the signals with respect to various modules the interface connects to. What Is Circular Dependency And How To Avoid This Problem ? Agreed, we can achieve the same via cross module referencing or by including the files, both of which are known to be not a great solution. What Is Layered Architecture ? 1 What is Formal Verification? always_comb is sensitive to changes within content of a function, whereas always @* is only sensitive to changes to the arguments to the function. Question 4. System Verilog Interview Questions. ... button, else your test will be automatically submitted. Engineering 2021 , Engineering Interview Questions.com, on 300+ [UPDATED] System Verilog Interview Questions, It is used to specify synchronization characteristics of the design, It Offers a clean way to drive and sample signals, Provides race-free operation if input skew > 0, Helps in testbench driving the signals at the right time, Can be declared inside interface,module or program, Object Oriented Programming for Hardware Verification, Improve Your SystemVerilog OOP Skills by Learning Principles and Patterns, Enhancing SystemVerilog with AOP Concepts (On how to mimic AOP features in OOP, good for guyz coming from e background), $random system function returns a 32-bit signed random number each time it is called, $urandom system function returns a 32-bit unsigned random number each time it is called. A queue is a variable-size, ordered collection of homogeneous elements. In SV, we use mailbox to get data from different modules and compare the result. Data can be sent to a mailbox by one process and retrieved by another. A Queue is analogous to one dimensional unpacked array that grows and shrinks automatically. That implies that the constraint solver doesn’t follow the sequence in which the constraints are specified. Question 30. Type casting in SV can be done either via static casting (‘, ‘, ‘) or dynamic casting via $cast task/function. There is no type-checking done. A mailbox is a communication mechanism that allows messages to be exchanged between processes. What Is The Difference Between Rand And Randc? This Verilog quiz is crafted to test your concepts across a broad range of fundamental Verilog concepts. 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The content inside the package can be accessed using either scope resolution operator (::), or using import (with option of referencing particular or all content of the package). Even the procedural looking constrains like if … else … and -> constrains, both if and else part are tried to solve concurrently. There are mainly following ways to avoid the race condition between testbench and RTL using system verilog. Practice and Preparation is quite essential for anyone looking for a job as a verification engineer. It’s hard to insert the data within the queue. class Scoreboard extends vmm_xactor; Packet_channel drvr2sb_chan; Packet_channel rcvr2sb_chan; function new(string inst = “class”, int unsigned stream_id = -1, Packet_channel drvr2sb_chan = null, Packet_channel rcvr2sb_chan = null); super.new(“sb”,inst,stream_id); if(drvr2sb_chan == null) `vmm_fatal(this.log,”drvr2sb_channel is not constructed”); else this.drvr2sb_chan = drvr2sb_chan; if(rcvr2sb_chan == null) `vmm_fatal(this.log,”rcvr2sb_channel is not constructed”); else this.rcvr2sb_chan = rcvr2sb_chan; `vmm_note(log,”Scoreboard created “);endfunction:new, task main(); Packet pkt_rcv,pkt_exp; string msg; super.main(); forever begin rcvr2sb_chan.get(pkt_rcv); $display(” %0d : Scoreboard : Scoreboard received a packet from receiver “,$time); drvr2sb_chan.get(pkt_exp); if(pkt_rcv.compare(pkt_exp,msg)) $display(” %0d : Scoreboard :Packet Matched “,$time); else `vmm_error(this.log,$psprintf(” Packet MissMatched n %s “,msg)); endendtask : mainendclass. In this article, we look at 10 knowledge-based Verilog questions and examples of successful answers. Initial block doesn’t have any such restrictions of execution in zero time (and can have delay, wait and non-blocking statements). Q1. – Clock specification – Input skew,output skew – Cycle delay (##), 01.Module M1(ck, enin, din, enout, dout);02.input ck,enin;03.input [31:0] din ;04.output enout ;05.output [31:0] dout ;06. FUNCTIONAL VERIFICATION QUESTIONS (Q i1)Explaino ehowi tooinject qare crc ierroroq jinre a ipacket owhichqhas justz datau yande ocrczx fields. Interview Questions & Answers Part – 5 (Verilog & System verilog) February 11, 2020 Interview Questions & Answers Part – 4 (Verilog & System verilog) January 24, 2020 Let’s Learn Perl (Part-7) Pattern Matching (Part-II) January 13, 2020 Here, you may find the most frequently asked Interview Questions on SystemVerilog, UVM, Verilog, SoC . The desperation of high tech firms is evident in aggressive job posts offering paid relocation, bonuses and other incentives. data_u; Now here XYZ union can contain either bit [31:0] data or an int data. It can be driven and read. Inside a program block, program variable can only be assigned using blocking assignment and non-program variables can only be assigned using non-blocking assignments. What Are The Ways To Avoid Race Condition Between Testbench And Rtl Using Systemverilog? Most Asked Technical Basic CIVIL | Mechanical | CSE | EEE | ECE | IT | Chemical | Medical MBBS Jobs Online Quiz Tests for Freshers Experienced. What are the ways to avoid race condition between testbench and RTL using SystemVerilog? To have bidirectional short-circuit connection SystemVerilog has added alias statement. How To Check Weather A Handles Is Holding Object Or Not ? More generally, the term factory method is often used to refer to any method whose main purpose is creation of objects. In SystemVerilog based constrained random verification environment, the test environment is divided into multiple layered as shown in the figure. What Data Structure You Used To Build Scoreboard? Final block can be used to display statistical/genaral information regarding the status of the execution like this:-, 1.final begin2.$display(“Simulation Passed”);3.$display(“Final value of xyz = %h”,xyz);4.$display(“Bye :: So long, and Thanks for all the fishes”);5.end. How To Randomize Dynamic Arrays Of Objects? Whenever an union is defined as tagged, it stores the tag information along with the value (in expense of few extra bits). The factory method design pattern handles this problem by defining a separate method for creating the objects, whose subclasses can then override to specify the derived type of product that will be created. Question 12. If you know answers to any of these then you are well come to share the same by commenting to this post. What Is The Dfference Between Always_combo And Always@(*)? 1.typedef union{2.bit [31:0] a;3.int b;4.} //define register variables. $monitor can be selectively enabled or disabled … The function new() is the class constructor function in SystemVerilog. extern keyword allows out-of-body method declaration in classes. Another big advantage of virtual interface is that class can dynamically connect to different physical interfaces in run time. Question 11. Question 27. But the probability of choosing a particular solution change by it. The blocking assignment statement (= operator) acts much like in traditional programming languages. Queues can be used to model a last in, first out buffer or first in, first out buffer. Question 5. (Verilog interview questions that is most commonly asked) The Verilog language has two forms of the procedural assignment statement: blocking and non-blocking. 07.clocking sd @(posedge ck);08.input #2ns ein,din ;09.output #3ns enout, dout;10.endclocking:sd11. HDL design and verification engineers are being absorbed by the job market faster than universities can create them. Report a Bug or Comment on This section - Your input is what keeps Testbench.in improving with time! But Linkedlist can easily insert the data in any location. Question 17. It serves these purposes, Having said this the major difference between module and program blocks are. What Is Solve And Before Constraint ? (a==0) || (b==1)). An union is used to stored multiple different kind/size of data in the same storage location. What Is The Need Of Alias In Sv? Question 28. No such restrictions on module, Program blocks get executed in the re-active region of scheduling queue, module blocks get executed in the active region. Question 39. In the case where we want to enforce that the read-back data-type is same as the written data-type we can use tagged union which is declared using the qualifier tagged. Or in simple terms factory pattern help in creation of the object when you dont know the exact type of the object. If it is a complex always block statement like always (@ posedge clk or negedge reset_), always @(posedge clk or negedge reset_) begin, if(!reset_) begin data <= '0; end else begin data <= data_next; endend, // Using forever : slightly complex but doable, forever begin fork begin : reset_logic @ (negedge reset_); data <= '0; end : reset_logic begin : clk_logic @ (posedge clk); if(!reset_) data <= '0; else data <= data_next; end : clk_logic join_any disable forkend. Download PDF - System Verilog Interview Questions And Answers [pld4e17r7wln]. a)0 b)X c)Z d)None of the above 2.Which logic level is not supported by verilog? It allows a lower-level software layer to call a subroutine (or function) defined in a higher-level layer. It helps in ensuring that testbench doesn’t have any race condition with DUT, It provides an entry point for execution of testbench. It can be written with a bit [31:0] data and read-back with a int data. What Is The Difference Between Program Block And Module ? Like other creational patterns, it deals with the problem of creating objects (products) without specifying the exact class of object that will be created. There are many difference between initial and final block. C Interview Questions. Question 37. class ABC;// Dynamic arrayrand bit [7:0] data [];// Constraintsconstraint cc {// Constraining sizedata.size inside {[1:10]};// Constraining individual entrydata[0] > 5;// All elementsforeach(data[i])if(i > 0)data[i] > data[i-1];|}endclass : ABC. Queue has a certain order. It is defined in a class to initialize data members of the class. “this” pointer refers to current instance. A blog to collect the interview questions and answer for ASIC related positions. Verilog interview questions - Verilog interview questions and answers for Freshers and Experienced candidates to help you to get ready for job interview, After preparing these Verilog programming questions pdf, you will get placement easily, we recommend you to read Verilog Interview questions before facing the real Verilog interview questions Freshers Experienced Question 23. Modports are part of Interface. A small SystemVerilog code snippet to illustrate #5, 01.module dummy;02.logic a, b, c, x, y;03. 16.program main;17.base_class my_class_object;18. If you are preparing to interview for a position that uses the Verilog language, you need to be familiar with some of the most commonly asked Verilog interview questions. Its not a actual hardware register but it can store values. Wires are used for connecting different modules. But they needed to be driven from verification environment like class. //define register variables. But later on, System Verilog and Verilog has merged into a new IEEE standard 1800-2009. Using covergroup : variables, expression, and their cross. 10.function void my_or;11.input a; // b and c are hidden input here12.y = a | b | c;13.endfunction : my_xor14. 06.// Tagged union expression07.data_tagged_u data1 = tagged a 32’h0;08.data_tagged_u data2 = tagged b 5;09. Analogous to picking of card from a deck of card without replacing. The output of the last shift register is fed to the input of the first register. To solve this issue virtual interface concept was introduced in SV. the normal way of creating the object is : 01.// Normal Type based object creation02. data_tagged_u;05. class Scoreboard;mailbox drvr2sb;mailbox rcvr2sb; function new(mailbox drvr2sb,mailbox rcvr2sb); this.drvr2sb = drvr2sb; this.rcvr2sb = rcvr2sb;endfunction:new, task start(); packet pkt_rcv,pkt_exp; forever begin rcvr2sb.get(pkt_rcv); $display(” %0d : Scorebooard : Scoreboard received a packet from receiver “,$time); drvr2sb.get(pkt_exp); if(pkt_rcv.compare(pkt_exp)) $display(” %0d : Scoreboardd :Packet Matched “,$time); else $root.error++; endendtask : startendclass. Question 13. It provides syntactic context (via program … endprogram) that specifies scheduling in the Reactive Region. It can contain module/class/function/task/constraints/covergroup and many more declarations (for complete list please refer section 18.2 of SV LRM 3.1a). All the variables are looked simultaneously. 04.initial begin05.MIN = 50; 06.for ( int i = 0;i begin 07.if( randomize(var) with { var < 100 ; var > MIN ;}) 08.$display(” Randomization sucsessfull : var = %0d Min = %0d”,var,MIN);09.else 10.$display(“Randomization failed”);11.end12. For example, in a 4-register counter, with initial register values of 1100, the repeating pattern is: 1100, 0110, 0011, 1001, 1100, so on. So the code will look like:-, 01.usb_packet My_usb_packet;02….03.if(My_usb_packet == null) begin04.// This loop will get exited if the handle is not holding any object05…..06.end else begin07.// Hurray … the handle is holding an object08….09.end. Ans: Crc ierroro einjecttioni canobe qdonere by imodifyingoq jthere crc ivalue oonly.q If idatao eisi modifiedoto qinjectre crc ierror,oq jthenre it imay oendqup inz au ysituatione othatzx the new modified packet may have the same crc. Virtual interface is a data type (that implies it can be instantiated in a class) which hold reference to an interface (that implies the class can drive the interface using the virtual interface). SVA ( System verilog Assertion) 1. Question 26. A. VHDL B. Verilog C. C D. C++ Answer: A Modules don’t have any such restrictions. For example (a==0) -> (b==1) shall be solved as all the possible solution of (! System verilog interview questions, verification engineer interview questions.