VHDL

Vhdl signed adder source

VHDL (VHSIC Hardware Description Language) is a hardware description language used in electronic design automation to describe the behavior and structure of electronic systems. VHDL can be used to describe the design at various levels of abstraction, from the system level down to the gate level.

History

VHDL was developed in the 1980s under the Very High-Speed Integrated Circuit (VHSIC) program initiated by the United States Department of Defense. The language was standardized by the Institute of Electrical and Electronics Engineers (IEEE) as IEEE 1076 in 1987.

Language Features

VHDL is a strongly typed language and supports a wide range of modeling capabilities, including:

• Behavioral modeling
• Dataflow modeling
• Structural modeling
• Mixed-level modeling

Data Types

VHDL supports a variety of data types, including:

• Scalar types (e.g., integer, real, boolean)
• Composite types (e.g., array, record)
• Access types (e.g., pointer)
• File types

Concurrent and Sequential Statements

VHDL allows the use of both concurrent and sequential statements. Concurrent statements are used to describe the parallel nature of hardware, while sequential statements are used within processes to describe algorithms.

Libraries and Packages

VHDL supports the use of libraries and packages to promote code reuse and modularity. Commonly used libraries include the IEEE library, which provides standard logic types and arithmetic functions.

Applications

VHDL is widely used in the design and verification of digital systems, including:

• Application-specific integrated circuits (ASICs)
• Field-programmable gate arrays (FPGAs)
• Digital signal processing (DSP) systems
• Microprocessors

Advantages

Some of the advantages of using VHDL include:

• Strong typing and rigorous syntax, which help in catching errors early in the design process
• Support for multiple levels of abstraction
• Portability across different hardware platforms
• Extensive support for simulation and verification

Related Pages

• Verilog
• SystemVerilog
• Hardware description language
• Electronic design automation
• Digital circuit
• FPGA
• ASIC

See Also

• IEEE 1076
• VHSIC
• Simulation
• Synthesis