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Verilog is a hardware description language (HDL) used to model electronic systems. It is most commonly used in the design and verification of digital circuits at the register-transfer level of abstraction. Verilog allows for the description of systems ranging from chip level to the architectural level, and it is widely used in field-programmable gate array (FPGA) and application-specific integrated circuit (ASIC) design. The language supports both behavioral and structural modeling. Behavioral modeling describes how a system operates, while structural modeling describes how components are connected together to form a system. Verilog was first developed by Gateway Design Automation in 1984, but it has since been standardized as IEEE Standard 1364. It has undergone several updates over time with added features like improved testbench support, four-value logic simulation capability, among others. Despite its wide usage in industry settings for hardware design, Verilog also serves as an educational tool for students studying digital logic or computer architecture courses due to its simplicity and ease of understanding compared to other HDLs such as VHDL.

Ask the right questions secure the right Verilog talent among an increasingly shrinking pool of talent.

First 20 minutes

General Verilog app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Verilog application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

What are the basic data types used in Verilog?

The basic data types used in Verilog are: Nets (wire), Registers (reg), Integer, Real, Time, and Event.

How would you define a module in Verilog?

A module is defined using the 'module' keyword followed by the module name, list of ports, and the module body enclosed within a pair of parentheses. For example: module ModuleName (input a, output b);

What are the different types of modeling in Verilog?

The different types of modeling in Verilog are: Gate Level Modeling, Dataflow Modeling, Behavioral Modeling, and Switch Level Modeling.

How would you implement a D flip-flop in Verilog?

A D flip-flop can be implemented using an always block and non-blocking assignment. For example: always @(posedge clk) begin q <= d; end

What is the difference between blocking and non-blocking assignments in Verilog?

Blocking assignments (=) execute in the order they are encountered, blocking subsequent assignments until they are completed. Non-blocking assignments (<=) allow assignments to execute in parallel.

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What you’re looking for early on

Does the candidate exhibit a deep understanding of Verilog language?

Has the candidate demonstrated experience with hardware description languages (HDLs)?

Is the candidate comfortable with debugging Verilog codes?

Can the candidate effectively work with EDA tools?

Next 20 minutes

Specific Verilog development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you define a two-dimensional array in Verilog?

A two-dimensional array can be defined in Verilog using the following syntax: reg [3:0] array_name [0:7]; This creates an 8 element array, each with 4 bits.

Describe the difference between initial and always block in Verilog.

The 'initial' block is executed only once at the start of simulation, while the 'always' block is executed throughout the simulation whenever the specified event occurs.

What are the different types of system tasks in Verilog?

System tasks in Verilog include $display, $monitor, $write, $stop, $finish, $time, and $random, among others.

How would you implement a four-bit counter in Verilog?

A four-bit counter can be implemented using an always block and non-blocking assignment. For example: always @(posedge clk) begin counter <= counter + 1'b1; end

Describe the difference between $finish and $stop system tasks in Verilog.

$finish stops the simulation and returns control to the operating system while $stop halts the simulation and returns control to the simulator command level.

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At this point, a skilled Verilog engineer should demonstrate strong problem-solving abilities, proficiency in Verilog programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Verilog.

What does the following Verilog code do?
module AND_Gate (input a, b, output c); assign c = a & b; endmodule
This code defines a simple AND gate in Verilog. It takes two inputs 'a' and 'b', performs a bitwise AND operation on them and assigns the result to the output 'c'.
What is the output of the following Verilog code?
module test; reg [3:0] a; initial begin a = 4'b1010; $display("%b", a); end endmodule
This code will display '1010'. It first declares a 4-bit register 'a', assigns the binary value '1010' to 'a', then displays the binary value of 'a'.
What does the following Verilog code do?
module shift (input [7:0] a, output [7:0] b); assign b = a >> 2; endmodule
This Verilog code defines a shift module. It takes an 8-bit input 'a' and performs a right shift operation by 2 places on 'a', then assigns the result to the 8-bit output 'b'.
What will be the output of the following Verilog code?
module test; reg a, b; wire c; assign c = a & b; initial begin a = 1'b0; b = 1'b1; #10 $display("%b", c); end endmodule
This code will display '0'. It first declares two registers 'a' and 'b', assigns binary values '0' and '1' to 'a' and 'b' respectively, then performs a bitwise AND operation on 'a' and 'b'. The result is assigned to the wire 'c', and after a delay of 10 time units, the binary value of 'c' is displayed.

Wrap-up questions

Final candidate for Verilog Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Verilog application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the different types of delays in Verilog?

There are three types of delays in Verilog: Gate delay, Interconnect delay, and Behavioral delay.

How would you implement a shift register in Verilog?

A shift register can be implemented using an always block and non-blocking assignment. For example: always @(posedge clk) begin shift_reg <= shift_reg << 1; end

What is the difference between procedural and continuous assignments in Verilog?

Procedural assignments happen inside procedural blocks (initial, always) and can be executed in a sequential manner. Continuous assignments are used to drive values onto nets and are concurrent in nature.

Verilog application related

Product Perfect's Verilog development capabilities

Beyond hiring for your Verilog engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Verilog projects, and can engage in multiple capacities.

Verilog Consultive assessments

Verilog Application Conversion Assessment Verilog Application Integration Assessment Verilog Data & Database Integration Assessment

Custom Verilog development projects

Custom Verilog App Conversion Verilog Custom App Development Process App UI Design for Verilog Facelifts

Hiring guide for Verilog Engineers

Verilog Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the Verilog engineer at this point.

Verilog Consultive assessments

Custom Verilog development projects