MAX + plus II: FPGA Integrated Digital Device Development Environment
The general tendency for the development of the element base of digital circuitry, starting with the appearance of the first integrated circuits in the early 60s to the present, is a continuous increase in the number of logic elements (LEs) placed on the chip, while reducing the unit cost of one element. An increase in the number of LEs continuously opens up the possibility of creating increasingly complex digital devices placed on a single chip. The main (far from complete) positive results of this trend include:
constant expansion of functionality and improvement of consumer properties of final products;
reduction in size and power consumption;
A reflection of this trend in the elemental base of digital circuitry was the transition from integrated circuits (ICs) of small and medium degrees of integration to large (LSI) and super-large (VLSI) integrated circuits. One of the most revolutionary results in the development of microelectronics was the possibility of creating the first microprocessors (early 70s), which gave a powerful impetus to the introduction of digital information processing technologies in all areas of human activity.
However, far from all the practical tasks of digital circuitry can be solved only using microprocessors alone. This is due to the feature that is organically inherent in all microprocessors and is related to the fact that the solution of any task by a microprocessor always consists of a sequence of steps of finite duration, while for solving many problems (including those related to ensuring the operation of the microprocessors themselves) devices with minimal delay are required perform logical functions. There are three main ways to meet this need:
The use of standard discrete digital logic sets of general application, for example, 74-series logic chipsets (TTL, CMOS) and typical peripheral LSIs.
Using custom VLSI.
Use of programmable logic integrated circuits (FPGAs).
For a long time, sets of discrete digital logic of various series have been the main element base for the development of digital devices. The composition of such kits includes a large number of individual microcircuits designed both to perform basic logical functions (AND, OR, NOT) and to perform the functions of typical digital devices, such as triggers, registers, counters, multiplexers, decoders, etc. , which makes it possible to use them to develop more complex functionally complete digital devices.
The main disadvantage of discrete logic is that the development of end products usually requires a large number of chips. The consequence of this is the large number of external connections, the complexity of the design and the large dimensions of the printed circuit boards, the large length of the connecting conductors, the complexity of constructing devices with a high clock frequency, and low reliability. To reduce the number of microcircuits in the design of microprocessor systems, a number of peripheral LSIs have been developed, which are specialized digital devices designed to perform some typical functions as part of microprocessor systems, such as dynamic RAM controllers, interrupt controllers, direct memory access controllers, bus controllers, etc. .d. However, even the use of peripheral LSIs does not completely overcome the main disadvantages of discrete digital logic.
The most cardinal problem of dimensions, speed, simplification of PCB designs and reliability is solved by developing and manufacturing custom VLSIs (a classic example is the chipsets of motherboards and expansion cards for personal computers). Unfortunately, this way is economically justified only for large-scale production of the same type of final product, due to the high cost and long lead times for the production of custom VLSI. In addition, when using custom VLSI, the possible modification of products requires significant additional material and time costs.
At the same time, in practice quite often there are requirements for the development of original digital devices and products that are not designed for large-scale production, for which the development of custom VLSI is not acceptable either for economic reasons or for terms of execution. For a long time, the only way to solve such problems was to use discrete logic integrated circuits and peripheral LSIs, since the capabilities of the first generations of simple FPGAs were very limited, and the price of complex FPGAs was very high, in addition, there were some difficulties with the design of digital devices for FPGAs .
In recent years, however, there has been a sharp breakthrough both in the technology of manufacturing FPGAs and in the development of tools for designing digital devices on FPGAs and manufacturing finished products.