10 Differences Between verilog and vhdl

Difference between Verilog and VHDL

Are you interested in digital design and hardware description languages? Verilog and VHDL are two popular hardware description languages used to model and simulate digital systems. In this article, we’ll explore the differences between Verilog and VHDL and understand their uses in the field of digital design.

What is Verilog?

Verilog is a hardware description language (HDL) used to design and simulate digital systems. It was developed by Phil Moorby in the early 1980s and has been widely adopted in the industry. Verilog allows designers to describe and model digital circuits, modules, and systems to be implemented on electronic devices such as field-programmable gate arrays (FPGAs) and application-specific integrated circuits (ASICs).

Examples of Verilog

Here’s a simple example of a Verilog code that describes a 2-to-1 multiplexer:

module mux2to1(input wire a, b, sel, 
               output wire y);
   assign y = (sel) ? b : a;

Uses of Verilog

Verilog is widely used in various electronic design automation (EDA) tools and applications:

  • Designing and verifying digital systems
  • Creating and simulating complex digital circuits
  • Synthesizing hardware designs for implementation on FPGAs and ASICs
  • Creating testbenches for functional verification

What is VHDL?

VHDL (VHSIC Hardware Description Language) is another popular hardware description language used for digital design. It was developed by the U.S. Department of Defense in the 1980s and has since become an IEEE standard (IEEE 1076). VHDL is widely adopted in the industry and is used for modeling, simulating, and synthesizing digital systems.

Examples of VHDL

Here’s a simple example of a VHDL code that describes the same 2-to-1 multiplexer:

entity mux2to1 is
   port(a, b : in std_logic;
        sel : in std_logic;
        y : out std_logic);
end mux2to1;

architecture behavior of mux2to1 is
   y <= b when sel = '1' else a;
end behavior;

Uses of VHDL

VHDL finds applications in various stages of the design process:

  • Designing and verifying digital systems
  • Creating behavioral or RTL (Register Transfer Level) models
  • Synthesizing hardware designs for implementation on FPGAs and ASICs
  • Creating testbenches for functional verification

Differences between Verilog and VHDL

Difference Area Verilog VHDL
Typing system Weak Strong
Conciseness More concise syntax Longer syntax, more verbose
Language origin Based on the C programming language Dominated by ADA language features
Simulation performance Faster simulation speed Relatively slower simulation speed
Event-driven modeling Naturally suited for event-driven modeling Supports both structural and behavioral modeling styles
Tool support Widely supported by EDA tools Supported, but not as widely as Verilog
Concurrency Concurrent statements are implicit Concurrent statements must be explicitly defined
Standard version IEEE 1364 IEEE 1076
Case sensitivity Case sensitive Not case sensitive
File extension .v .vhdl or .vhd


In conclusion, both Verilog and VHDL are powerful hardware description languages used for modeling and simulating digital systems. Verilog is known for its concise syntax, weaker typing system, and faster simulation speed, making it a popular choice for many designers. On the other hand, VHDL has a more verbose syntax, stronger typing system, and wider support for structural and behavioral modeling styles. The choice between Verilog and VHDL often depends on individual preferences, project requirements, and tool availability.

People Also Ask

Here are some common questions about Verilog and VHDL:

Q: Which one should I learn - Verilog or VHDL?
A: The choice depends on your specific requirements, project constraints, and tool availability. Both languages are widely used, so learning either one will enhance your digital design skills.

Q: Can I use Verilog code in a VHDL project, or vice versa?
A: Generally, it is not recommended to mix Verilog and VHDL code directly. However, both languages can be compiled or synthesized together using mixed-language simulation and synthesis tools.

Q: Are Verilog and VHDL compatible with each other?
A: Verilog and VHDL can coexist in the same design project, but they have different syntax and coding styles. Interoperability between the two languages can be achieved using dedicated conversion tools or language constructs.

Q: Which language is more widely adopted in the industry?
A: Verilog is more widely adopted in the industry due to its concise syntax, faster simulation speed, and extensive tool support. However, VHDL is still prevalent, especially in industries that require stronger typing and richer modeling features.

Q: Can I use Verilog or VHDL for software programming?
A: Verilog and VHDL are hardware description languages specifically designed for modeling and simulating digital systems. They are not intended for software programming, but rather for hardware design and verification.

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