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Lexical Tokens

Behavioral Modeling

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Lexical tokens are the basic building blocks of Verilog code that are keywords, identifiers, operators. They are like a way of communicating with the language and are useful for constructing Verilog statements and expressions. Some of the lexical tokens are:
a. White space

b. Comments

c. Numbers

d. Operators

e. Identifiers and Keywords

f. Datatypes

1. Nets

2. registers

g. Module declaration

White Space

In Verilog, we use this white spaces in output commands like $display, $monitor, $strobe etc. In this “\t” represents tab space, “\n” represents new line.

Comments

There are 2 ways for writing comments in Verilog. One way is to enclose the comment in “/*……..*/” . This will be helpful when there are multi-lined comments. and another way is to append “//” at the beginning of the sentence. This will be helpful for writing comments that are single-lined or of short context. 

/*
This is an example for Multi-lined comment.
Hello there
welcome to Verilog tutorial 
*/

//this is a example for single line comment. 
//Hello there.

Getting Started with Verilog

For a long time, computer programming languages like FORTRAN, Pascal, and C were used to describe computer programs and their code execution is sequential. But there isn’t any language to describe the digital circuits. This is when Hardware Description Language(HDL) came into play. HDLs are even popular for verification purposes. There are mainly two types of HDL:

  • Verilog HDL
  • VHDL (Very High-Speed was Integrated Circuit (VHSIC) Hardware Description Language)

Note: Verilog HDL and VHDL aren’t the same. VHDL was used before Verilog came into existence. the difference between them will be discussed in the later part.

Table of Content

  • What is Verilog?
  • Gate Level Modeling
  • Data-Flow Modeling
  • Behavioral Modeling
  • Operators
  • Identifiers and Keywords
  • Datatypes
  • Module Declaration
  • Classification of Verilog
  • Verilog HDL Vs VHDL

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What is Verilog?

Verilog is a hardware description language that is used to realize the digital circuits through code. Verilog HDL is commonly used for design(RTL) and verification(Test-bench) purposes for both Field programmable gate arrays(FPGA) and Application-specific Integrated Circuits(ASIC). There are mainly three levels of abstraction(Different perspectives or views at which a design can be viewed or analyzed) for writing in Verilog:...

Gate Level Modeling

If a circuit is represented completely using basic gates it is called gate level modeling. For example refer the below circuit of half adder where we can represent it simply using the AND and XOR gates. this level of abstraction involves describing the circuit using primitive logic gates such as AND, OR, XOR, etc. This level provides a detailed representation of the circuit’s structure and logic. Given Below is the RTL Code for Half Adder....

Data-Flow Modeling

Here in this level of abstraction we make use of the functions that define the working of the circuit instead of it’s gate structure. This abstraction level mainly focuses on the flow of data through the circuit logic gates or functional expressions....

Behavioral Modeling

This is the highest level of abstraction in Verilog. At this level the designers describe the functionality of the circuit without specifying the functionality and structure of digital circuit. This modeling will be helpful because it focuses on what the circuit should do rather than how it should be implemented....

Lexical Tokens

Lexical tokens are the basic building blocks of Verilog code that are keywords, identifiers, operators. They are like a way of communicating with the language and are useful for constructing Verilog statements and expressions. Some of the lexical tokens are: a. White space...

Numbers

There are mainly 4 used number systems in Verilog. They are...

Operators

There are mainly 3 types of operators, they are:...

Identifiers and Keywords

Identifier is the name given to a function, task or for a module in Verilog. These Identifiers must be in lowercase and they are case sensitive. Characters like Numbers, underscore, special characters like $ can be used for naming the identifier but they cannot be used as the first character of the identifier because they are reserved for some inbuilt function in Verilog....

Datatypes

There are 4 basic values in Verilog:...

Module Declaration

Given Below is the Code for module declaration...

Different Classification of Verilog

Verilog-1995: Verilog-1995, also known as IEEE Standard 1364-1995, is the initial version of Verilog that introduced the language’s basic syntax and features. It provides the fundamental constructs for describing digital circuits, including modules, ports, data types (wire, reg), and basic behavioral and structural modeling techniques. Verilog-2001: Verilog-2001, an extension of Verilog-1995, introduced several new features and enhancements to the language to improve code readability, re-usability, and ease of design. It addressed some limitations of the previous version and introduced new constructs for better modeling and verification. SystemVerilog: SystemVerilog is a significant extension of Verilog that adds new features and capabilities for both design and verification. It incorporates features from the Vera and Specman languages, providing a comprehensive solution for design, verification, and system-level modeling. Verilog-AMS (Analog and Mixed-Signal): Verilog-AMS is an extension of Verilog that enables modeling of analog and mixed-signal systems alongside digital logic. It provides constructs for describing continuous-time analog behavior, such as voltage and current, in addition to digital signals and logic....

Difference Between Verilog HDL and VHDL

Given Below is the Table for the difference between Verilog HDL and VHDL...

Advantages of Verilog

Concise Syntax: Verilog has a straightforward syntax that allows for quick and efficient coding of digital circuits. Industry Standard: It is widely used and accepted in the semiconductor industry, making it easier to collaborate with others and access resources. Simulation and Synthesis: Verilog supports both simulation and synthesis, allowing designers to verify their designs and translate them into actual hardware. Hierarchical Design: Verilog enables hierarchical design, which allows for the creation of complex systems by breaking them down into smaller, manageable modules....

Disadvantages of Verilog

Steep Learning Curve: Verilog can be a bit difficult to understand for beginners due to syntax and concepts and takes time to get proficient. Tool Dependency: Verilog design requires specialized tools for synthesis, simulation, and verification, which may come with associated costs and compatibility issues. Version Compatibility: Compatibility issues may arise when using different versions of Verilog or when interfacing with third-party tools and libraries. Verification Challenges: While Verilog supports simulation-based verification, establishing comprehensive test benches and ensuring complete coverage can be complex and time-consuming....

Applications of Verilog

Embedded Systems: Verilog is used to design hardware components in embedded systems like microcontrollers and FPGAs. Digital Signal Processing: Verilog enables the implementation of DSP algorithms in hardware for applications like audio and video processing. Networking: Verilog is utilized in the design of networking hardware such as routers, switches, and network interface cards. ASIC Design: Verilog is commonly employed in application-specific integrated circuit (ASIC) design for custom hardware implementations. Autonomous Vehicles: Verilog finds applications in automotive electronics for systems like engine control units and advanced driver-assistance systems (ADAS)....

Conclusion

Verilog is the digital design equivalent of a magic tool, enabling us to make incredible things in the field of electronics. From basic circuits to complex devices, Verilog enables us to explain their operation in a language that computers understand. Indeed, learning it can be a little challenging at first, but the opportunities are infinite once you get the hang of it!...

Getting Started with Verilog – FAQs

What are the best practices for writing efficient Verilog code?...

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#Getting Started #Verilog #Electronics Engineering

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