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Verilog Tutorial

Verilog is a Hardware Description Language (HDL). It is a language used for describing a digital system such as a network switch, a microprocessor, a memory, or a flip-flop. We can describe any digital hardware by using HDL at any level. Designs described in HDL are independent of technology, very easy for designing and debugging, and are normally more useful than schematics, particularly for large circuits.

What is Verilog?

Verilog is a HARDWARE DESCRIPTION LANGUAGE (HDL), which is used to describe a digital system such as a network switch or a microprocessor or a memory a flip-flop.

Verilog Tutorial

Verilog was developed to simplify the process and make the HDL more robust and flexible. Today, Verilog is the most popular HDL used and practiced throughout the semiconductor industry.

HDL was developed to enhance the design process by allowing engineers to describe the desired hardware's functionality and let automation tools convert that behavior into actual hardware elements like combinational gates and sequential logic.

Verilog is like any other hardware description language. It permits the designers to design the designs in either Bottom-up or Top-down methodology.

  • Bottom-Up Design: The traditional method of electronic design is bottom-up. Each design is performed at the gate-level using the standards gates. This design gives a way to design new structural, hierarchical design methods.
  • Top-Down Design: It allows early testing, easy change of different technologies, and structured system design and offers many other benefits.

Verilog Abstraction Levels

Verilog supports a design at many levels of abstraction, such as:

  • Behavioral level
  • Register-transfer level
  • Gate level

Behavioral level

The behavioral level describes a system by concurrent algorithms behavioral. Every algorithm is sequential, which means it consists of a set of executed instructions one by one. Functions, tasks, and blocks are the main elements. There is no regard for the structural realization of the design.

Register-Transfer Level

Designs using the Register-Transfer Level specify a circuit's characteristics using operations and the transfer of data between the registers.

The modern definition of an RTL code is "Any code that is synthesizable is called RTL code".

Gate Level

The characteristics of a system are described by logical links and their timing properties within the logical level. All signals are discrete signals. They can only have definite logical values (`0', `1', `X', `Z`).

The usable operations are predefined logic primitives (basic gates). Gate level modeling may not be the right idea for logic design. Gate level code is generated using tools such as synthesis tools, and his netlist is used for gate-level simulation and backend.

History of Verilog

  • Verilog HDL's history goes back to the 1980s when a company called Gateway Design Automation developed a logic simulator, Verilog-XL, and a hardware description language.
  • Cadence Design Systems acquired Gateway in 1989 and with it the rights to the language and the simulator. In 1990, Cadence put the language into the public domain, with the intention that it should become a standard, non-proprietary language.
  • The Verilog HDL is now maintained by a nonprofit making organization, Accellera, formed from the merger of Open Verilog International (OVI) and VHDL International. OVI had the task of taking the language through the IEEE standardization procedure.
  • In December 1995, Verilog HDL became IEEE Std. 1364-1995. A significantly revised version was published in 2001: IEEE Std. 1364-2001. There was a further revision in 2005, but this only added a few minor changes.
  • Accellera has also developed a new standard, SystemVerilog, which extends Verilog.
  • SystemVerilog became an IEEE standard (1800-2005) in 2005.

How is Verilog useful?

Verilog creates a level of abstraction that helps hide away the details of its implementation and technology.

For example, a D flip-flop design would require the knowledge of how the transistors need to be arranged to achieve a positive-edge triggered FF and what the rise, fall, and CLK-Q times required to latch the value onto a flop among much other technology-oriented details.

Power dissipation, timing, and the ability to drive nets and other flops would also require a more thorough understanding of a transistor's physical characteristics.

Verilog helps us to focus on the behavior and leave the rest to be sorted out later.


Before learning Verilog, you should have a basic knowledge of VLSI Design language.

  • You should know how Logic diagrams work, Boolean algebra, logic gates, Combinational and Sequential Circuits, operators, etc.
  • You should know about Static timing analysis concepts such as setup time, hold time, critical path, limits on clock frequency, etc.
  • ASIC and FPGA basics and Synthesis and simulation concepts.


Our Verilog tutorial is designed to help beginners, Design Engineers, and Verification Engineers who are willing to learn how to model digital systems in the Verilog HDL to allow for automatic synthesis. By the end of this tutorial, you will have gained an intermediate level of expertise in Verilog.


We assure you that you will not find any problem with the Verilog Tutorial. But if there is any mistake, please post the question in the contact form.

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