Introduction to HDL

Posted by Srihari Rao On Sunday, December 16, 2012 1 comments
HDL - VHDL and Verilog

There are many programming languages being used today for many purposes. In those HDL is one programming language. Then today let us learn what is this HDL and why it is used.

Introduction to HDL

What is HDL and why HDL?

Hardware Description Language (HDL) is a Computer-Aided Design (CAD) tool for the modern design and synthesis of digital systems. It is used to verify complex designs before they are manufactured by any company. Once the design is made ready it is written in form of code and will test the components connections and behavior. Once it is verified thoroughly then the circuits will be manufactured. They are generally realized by programmable chips like Application-Specific Integrated  Circuits (ASIC) and FPGA's and would require CAD tools. HDL is one such CAD tool.

The designer uses HDL to describe any digital system in a computer language which is similar to high level language such as 'C'. There are two widely used HDL's. They are:

  1. VHDL
  2. Verilog
History of VHDL

VHDL stands for Very High Speed Integrated Circuit (VHSIC) Hardware Description Language. It was developed in early 1980's under the VHSIC program. Many companies were involved in designing VHSIC chips for US Department of Defense  At that time each company used their own HDL which provided them only gate level design tools. So the need for standard HDL was generated.

IBM, Texas Instruments and Intermetrics was given the work of developing a powerful standard HDL based tool by DoD. First publicly available standard was VHDL version 7.2 in 1985. In 1989 this VHDL was made to standardize by IEEE. In 1987 it became IEEE Standard 1076-1987.In 1993 VHDL was updated and more feature were added to it to become IEEE standard 1076-1993. 

History of Verilog

In 1983 Gateway Design Automation developed a hardware description language for its newly introduced logic simulator, Verilog-XL. In 1990 Verilog HDL was available as public domain. In 1995 Verilog HDL became IEEE standard 1364-1995. The language is currently maintained by the Open Verilog International (OVI) organization. Verilog code structure is based on C language. 

That's a brief introduction of HDL. We will be posting more about HDL like some basic programs to verify some digital circuits. In my next post i will be providing software to debug and run and your HDL codes.

Have anything to ask. Just comment below.



Efraín Gustavo Barragán Jácome said...

I found your article very interesting.
Congratulations from Mexico

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