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Table of contents
1.
Introduction
2.
What is Verilog?
3.
Strength of Verilog
4.
Weakness of Verilog
5.
What is VHDL?
6.
Strength of VHDL
7.
Weakness of VHDL
8.
Application of Verilog and VHDL
9.
Difference between Verilog and VHDL
10.
Frequently Asked Questions
10.1.
What are the different types of modelling in Verilog?
10.2.
Which is better, VHDL or Verilog?
10.3.
What are some common VHDL tools and simulators?  
11.
Conclusion
Last Updated: Mar 27, 2024

Difference between Verilog and VHDL

Author Rashmi
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Introduction

Verilog and VHDL are two popular Hardware Description Languages (HDLs) used for designing and simulating digital circuits. Despite having the same function, both languages have different syntaxes, design approaches, and applications.

difference between verilog and vhd

In this blog, we will discuss the difference between Verilog and VHDL language along with their strengths and weaknesses.

What is Verilog?

Verilog is a text-based hardware description language used to describe electronic systems and circuits. It is designed for logic synthesis, timing analysis, test analysis (including testability analysis and fault grading), and verification through simulation.

The IEEE Verilog standard document is the Language Reference Manual or LRM. The Verilog HDL is defined in its entirety and this authoritative definition.

Verilog defines four abstraction levels to implement modules and is primarily a structural and behavioral language. 

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

  • Behavioral level
  • Register-transfer level
  • Gate level
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Strength of Verilog

The strength of verilog are:-

  • Verilog is simple to learn and has a simple syntax, making it especially simple for people with programming experience.
     
  • It is widely used in the industry and has a sizable user base, so a wealth of support and information is available.
     
  • It offers a quick and easy way to simulate and test digital circuits before they are used.
     
  • It is simple to integrate with other design tools because it is compatible with a wide range of platforms and design tools.
     
  • The short syntax of Verilog enables quicker development and requires less code to be written.

Weakness of Verilog

The weakness of Verilog is:-

  • Verilog has limited abstraction support, which can make designing and verifying complex systems more challenging.
     
  • Verilog is weakly typed; errors involving data types might not be discovered until runtime.
     
  • Verilog does not offer as strong formal verification support as other languages, such as SystemVerilog, despite having simulation tools.
     
  • Verilog has poor concurrent programming support, making it challenging to design systems with intricate interconnections.
     
  • Verilog lacks object-oriented programming support, making designing and maintaining large, complex systems more challenging.
     
  • Verilog only provides a small amount of support for dynamic simulation, making it more difficult to design systems requiring runtime configuration changes.

What is VHDL?

VHDL is the Hardware Description Language. Under the guidelines of the VHSIC program, this language was first made available to the DoD in 1981.

 It is particularly well suited as a language to describe the structure and behavior of digital electronic hardware designs, such as ASICs and FPGAs, and traditional digital circuits. It can represent the behavior and structure of electronic systems.

An entity in VHDL describes a hardware module. To represent the entity, we can use the following:

  1. Entity declaration
  2. Architecture
  3. Configuration
  4. Package declaration
  5. Package body
     

The syntax for declaring entity:-

entity entity_name is
   Port declaration;
end entity_name;

Strength of VHDL

The strength of VHDL are:-

  • VHDL supports high-level abstraction very well, making it possible to design complex systems quickly.
     
  • VHDL is strongly typed, and data type errors are caught early in the development cycle.
     
  • Verification is well supported by VHDL, which has many built-in features for formal verification, simulation, and debugging.
     
  • VHDL has strong concurrent programming support, simplifying designing intricate connections between components.
     
  • VHDL has object-oriented programming support, simplifying designing and maintaining extensive, complex systems.
     
  • VHDL has good dynamic simulation support, enabling runtime configuration changes throughout the simulation.

Weakness of VHDL

The weakness of VHDL are:-

  • Steep learning curve: Compared to other hardware description languages, VHDL has a more complex syntax and is generally thought to be more challenging to learn.
     
  • Longer development time: Compared to other hardware description languages, VHDL may require more time to develop and debug due to its high level of abstraction and emphasis on verification.
     
  • The high level of abstraction in VHDL can make it challenging to optimize designs at a low level, which may limit performance.
     
  • Limited parallelism support: Despite VHDL's strong support for concurrent programming, the complexity of the language makes it challenging to achieve maximum parallelism.
     
  • Limited portability: Although VHDL is a standard language, some implementation differences between design tools and platforms may prevent full portability.

Application of Verilog and VHDL

Some applications of Verilog and VHDL are:-

  • FPGA design: Field-Programmable Gate Arrays (FPGAs), frequently employed in digital signal processing, video and audio processing, and control systems, are designed using Verilog.
     
  • Application-Specific Integrated Circuit (ASIC) design: Verilog is also used in ASIC design. Before the physical implementation of the chip, it is used to describe the behavior of circuits and to test the functionality of the design.
     
  • Processor Design: Verilog designs digital signal processors (DSPs), microcontrollers, and processors of all kinds.
     
  • Verification: Before using their design in hardware, designers can test and validate it using Verilog's simulation and verification tools for digital circuits.
     
  • System-on-Chip (SoC) design: Verilog is used to create SoCs, which are integrated circuits that include a variety of subsystems, including processors, memory, and other components.
     

Now, we wil see the difference between Verilog and VHDL in next section.

Difference between Verilog and VHDL

In this section, we will see a difference between Verilog and VHDL.

Verilog

VHDL

It is a hardware description language used for modeling electronic systems. It is a hardware description language used to describe digital and mixed-signal systems.
It is based on the C language. It is based on Ada and Pascal languages.
It is case-sensitive. It is case insensitive.
It is easier to learn. It takes work to learn.
It does not support a multidimensional array. It supports a multidimensional array.
Verilog does not allow concurrent task calls. VHDL allows concurrent procedure calls. 
It is a simple datatype. It is a complex datatype.
There is no concept of the library in Verilog. The library is present in VHDL.

Frequently Asked Questions

What are the different types of modelling in Verilog?

The various types of Verilog modelling include gate-level modelling, which describes the actual physical implementation of the circuit using logic gates, RTL modelling, which represents the registers and logic in the circuit; and behavioral modelling, which describes the functionality of a circuit.

Which is better, VHDL or Verilog?

VHDL and Verilog are both hardware description languages that are used in electronics design. The choice depends on project requirements and the ecosystem. VHDL is known for its strictness and readability because it is a strongly typed language, while Verilog is more compact, efficient and easy to read. 

What are some common VHDL tools and simulators?  

Xilinx ISE, Altera Quartus, ModelSim, GHDL, and Synopsys Design Compiler are just a few of the many VHDL tools and simulators. To assist in the design and verification of digital circuits, these tools offer a variety of features like syntax highlighting, code completion, waveform analysis, debugging, and synthesis.

Conclusion

Congratulations on finishing the blog!! Understanding the difference between Verilog and VHDL languages can help designers choose the right language for their design needs.

We hope this blog has helped you. We recommend you visit our articles on related topics, such as:

  1. Verilog Interview Questions
  2. Difference between BJT and Mosfet
  3. Difference between Parallel and Series Connections
     

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