VHDL is a hardware description language used in electronic design automation to describe digital and mixed-signal systems. VHDL can also be used as a general purpose programming language.
VHDL was originally developed at the behest of the United States Department of Defense in order to document the behavior of the ASICs that supplier companies were including in equipment. The idea was that if the government wanted to verify the equipment worked as specified, they could do so by reading the documentation. The language was first introduced in 1981, and the most recent standard was published in 2008.
VHDL is a declarative language, meaning that the programmer does not specify the order in which the operations are to be performed. This is in contrast to imperative languages, such as C, in which the programmer must specify the order of operations.
VHDL is used primarily in two ways:
* To design new digital hardware
* To verify the functionality of existing digital hardware
When used for design, VHDL code is synthesized into a logic circuit. This circuit can then be implemented on an FPGA or ASIC.
When used for verification, VHDL can be used to simulate the behavior of digital hardware. This allows for the detection of bugs and the testing of new designs before hardware is actually built.
VHDL has a number of features that make it well suited for use in electronic design automation:
* Hardware can be described at multiple levels of abstraction, from the behavior level to the gate level.
* VHDL is a text-based language, making it easy to use with existing text editors and tools.
* VHDL code can be reused, making it easy to design complex systems.
* VHDL is platform independent, meaning that code can be run on any computer.
VHDL is a complex language, and it can take some time to learn. However, there are a number of resources available to help, including books, online tutorials, and courses.