VHDL: software based hardware designs

In the VLSI (Very Large-Scale Integrated Circuits) era, a structured design process is required. An ideal design process can exist only if a language exists to describe hardware at various levels so that the managers, users, designers, testers, simulators, and machines can understand it. The IEEE standard VHDL hardware description language is such a language. Languages such as CDL (Computer Design Language), ISPS (Instruction Set Processor Specification), AHPL (A Hardware Programming Language), and IDL (Interactive Design Language) have been used in the past. Early in the VHSIC program it was found that none of the existing hardware description languages could be used as a standard tool for the design, manufacturing, and documentation of digital circuits to complete systems. VHDL was defined because a need existed for an integrated design and documentation language to communicate design data between various levels of abstraction. In this article, the authors describe the usefulness and impact of VHDL on the digital system designs and present some practical case studies.