What is HDL??

HDL is any language from a class of: Computer languages Specification languages Modeling languages

It is a textual description consisting of expressions, statements and control structures of:

the spatial and temporal structure and behavior of electronic systems

formal description and design of an electronic circuit and digital logic

allows for the automated analysis, simulation, and simulated testing of an electronic circuit.

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What is HDL??

HDL is any language from a class of: Computer languages Specification languages Modeling languages

It is a textual description consisting of expressions, statements and control structures of:

the spatial and temporal structure and behavior of electronic systems

formal description and design of an electronic circuit and digital logic

allows for the automated analysis, simulation, and simulated testing of an electronic circuit.

Purposes of HDL

simulation

synthesis

Simulation: First it is used to write a model for the expected behavior of the circuit before that circuit is designed and built. The model is fed into a computer program called a simulator which allows the designer to verify that the solution behaves correctly. This process is known as Hardware Simulation.

Synthesis: Second, it is used to write a detailed description of a circuit that is input into another computer program called a logic compiler. The output of the compiler is used to configure a programmable logic device such as an FPGA to perform the hardware function. This process is known as Hardware Synthesis.

Uses of HDL:

to write executable specifications for hardware.

to model a piece of hardware before it is created physically.

It is this executability that gives HDLs the illusion of being programming languages.

they are more precisely classified as specification languages or modeling languages.

Simulators capable of supporting discrete-event (digital) and continuous-time (analog) modeling exist, and HDLs targeted for each are available.

Different levels of Abstraction:

Architecture / Algorithm LevelDescribe the functionality (behavior) of a circuit

Register Transfer Logic (RTL) LevelDescribe the data flow of a circuit

Gate LevelDescribe the connectivity (structure) of a circuit

Switch Level

Design Flow of using HDL:

Why use the HDL ?

Difficult to design directly on hardware

Mixed-level modeling and simulation

Easier to explore different design options

Reduce design time and cost

These days, it would be impossible to design a complex system on a chip for a mobile device or any other consumer electronics product without an HDL.

Types of HDLs:

There are three types of HDLs

VHDL VERILOG SYSTEM VERILOG

VHDL and Verilog are considered general-purpose digital design languages, while SystemVerilog represents an enhanced version of Verilog. Each has its own style and characteristics. VHDL has roots in the Ada programming language in both concept and syntax, while Verilog’s roots can be tracked back to an early HDL called Hilo and the C programming language.

System Verilog includes a set of extensions to the Verilog HDL to help engineers design and verify larger and more complex designs.

 

Verilog 

  Verilog Similar to

C.   Popular in

commercial, on coasts of US.

  Designs contained

in “modules.

VHDL

Similar to Ada.

Popular in Military, Midwest US.

 

Designs contained in “entity” “architecture” pairs.

C programming:

General-purpose programming language

C program can be compiles for a very wide variety of commuter platforms and operating system

This language has become available to wide range of platforms and operating systems from embedded computers to supercomputers.

Difference b/w CPL & HDL

CPL

• C is a middle level language A mix of high level language and an assembly language.

• C can only handle sequential instructions.

• C program can successfully written with pure logical and algorithmic thinking

HDL

• HDL is a hardware description language It is uses for implementing the hardware circuit

• VHDL also allows both sequential and concurrent executions

• VHDL programmer needs thorough working knowledge of the hardware circuits. He should be able to predict how a given code will be implemented in hardware.

CPL

We don’t care about resource usage in C. Because C program runs on a computer which uses powerful processor with high speed.

HDL

The memory and other logic elements are limited in a FPGA. It is very difficult to implement image processing algorithms in VHDL than in C.

Advantages of HDL:

Advantages compared to traditional schematic-based design• Design with RTL description + logic

synthesis toolo Abstract levelo Independent to fabrication technologyo Reuse when fabrication technology

changing• Functional verification can be done early

o Optimized to meet the desired functionality

• Analogous to computer programmingo Textual description with comments

Conclusion:

Software programming languages and HDL are very different languages.

Because both have many basic level differences even if they seem to have few similarities.

In contrast to most software programming languages like C, HDLS includes n explicit notion of time which is the primary attribute of hardware.