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VHDL Overview
VHDL is an industry standard modeling language for the description and design of electronic systems. Although intended for the simulation of digital hardware designs, VHDL contains many features which are part of many other modern programming, hardware description and C.A.E. and simulation languages. The acronym VHDL stands for VHSIC Hardware Description Language, with VHSIC in turn referring to the Very High Speed Integrated Circuit program. This program sponsored by the Department of Defense (DoD) in 1981 had the aim of developing high-speed integrated circuits and involved several major DoD contractors.
VHDL supports a broad set of constructs that enable a digital design to be described at different levels of abstraction such as algorithmic, register transfer or logic gate level.
It offers several styles of design modeling. Behavioral style architecture consists of VHDL processes that provide a sequential description of the behavior of the design but include no information as to how the design is to implemented. The flow of control and the movement of data can also be specified in dataflow style architecture. It models the design in a concurrent environment in which several movements can happen at the same time. The dataflow style is therefore very suitable for describing the parallelism of data movement in a digital design. Finally structural style architecture permits structural implementation using component declarations and instantiations. It comprises a list of concurrently active components and their interconnections.
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