Languages for integrated circuit design

The second half of the twentieth century will be remembered as the era of the invention and proliferation of integrated circuits and the electronic systems built around them. Calculators existed before, but they were mechanical. In the 21st century, these calculators, now microprocessors, will be no more than a component of a "system-on-a-chip". On this chip, other mutations will take place: optical, micromechanical (already mastered), molecular, even biological.

In fact, all these aspects are merely the wrapping of mathematical machines. This has always been perceptible in the field of software, where high-level languages or machine languages are more or less rigorous, but immaterial, variations on the notions of automaton functions, algorithms or processes.

But a machine, even a mathematical one, needs a physical support, just as information needs the support of mass and energy. This support is the electronic hardware, integrated circuits and peripherals.

The invention of circuit design languages ("Hardware Description Language": HDL) – which had not yet been integrated – dates back to the early 1960s in both the USA and Europe. It was motivated by the desire to keep the design process at an abstract level for as long as possible, and to postpone the transition to physical implementation until such time as no decision could be taken independently of the technology. It was also a response to the continuous and exponential growth in the complexity of the electronic systems to be designed, a problem common to both hardware and software, which may explain why the syntax of HDL languages followed the evolution of programming languages with a reasonable ten-year lag. At the end of the 1960s, it was "Algol", a decade later "Pascal", then in the 1980s "C" or "ADA". These HDLs also incorporated the most advanced concepts of program specification languages. When it comes to specifying a complete system (digital circuits, analog circuits, sensors, software) integrated on a single chip, there will be no difference. Although HDL languages can describe some of the constraints imposed by a technology (temporal, topological, resolution functions...), these can be treated as external parameters. The language domain is that of abstract objects, theoretically capable of being realized with any technology, provided that suitable design support software is provided.

This creates a new situation. On the one hand, because of their complexity, which can no longer be mastered even by very large design teams, the systems to be designed require all the CAD software available. Even more efficient CAD software will undoubtedly be developed, but conversely, the circuits designed will be increasingly limited to those that the CAD software of...