VHSIC Hardware Description Language
| Paradigm | concurrent, reactive |
|---|---|
| First appeared | 1980s |
| Typing discipline | strong |
| Website | IEEE VASG |
| Influenced by | |
| Ada, Pascal | |
VHDL (VHSIC Hardware Description Language) is a hardware description language used in electronic design automation to describe digital and mixed-signal systems such as field-programmable gate arrays and integrated circuits. VHDL can also be used as a general purpose parallel programming language.
VHDL was originally developed at the behest of the U.S Department of Defense in order to document the behavior of the ASICs that supplier companies were including in equipment.
The idea of being able to simulate the ASICs from the information in this documentation was so obviously attractive that logic simulators were developed that could read the VHDL files. The next step was the development of logic synthesis tools that read the VHDL, and output a definition of the physical implementation of the circuit.
Due to the Department of Defense requiring as much of the syntax as possible to be based on Ada, in order to avoid re-inventing concepts that had already been thoroughly tested in the development of Ada, VHDL borrows heavily from the Ada programming language in both concepts and syntax.
The initial version of VHDL, designed to IEEE standard IEEE 1076-1987, included a wide range of data types, including numerical (integer and real), logical (bit and boolean), character and time, plus arrays of bit called bit_vector and of character called string.
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