Essay About Complex Plds And Logic Circuits

Electrical Engineering
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Architecture of FPGAs and CPLDs: A Tutorial
Abstract
This paper provides a tutorial survey of architectures of commercially available high-capacity
field-programmable devices (FPDs). We first define the relevant terminology in the field and then
describe the recent evolution of FPDs. The three main categories of FPDs are delineated: Simple
PLDs (SPLDs), Complex PLDs (CPLDs) and Field-Programmable Gate Arrays (FPGAs). We
then give details of the architectures of all of the most important commercially available chips,
and give examples of applications of each type of device.
1 Introduction to High-Capacity FPDs
Prompted by the development of new types of sophisticated field-programmable devices (FPDs),
the process of designing digital hardware has changed dramatically over the past few years.
Unlike previous generations of technology, in which board-level designs included large numbers
of SSI chips containing basic gates, virtually every digital design produced today consists mostly
of high-density devices. This applies not only to custom devices like processors and memory, but
also for logic circuits such as state machine controllers, counters, registers, and decoders. When
such circuits are destined for high-volume systems they have been integrated into high-density
gate arrays. However, gate array NRE costs often are too expensive and gate arrays take too long
to manufacture to be viable for prototyping or other low-volume scenarios. For these reasons,
most prototypes, and also many production designs are now built using FPDs. The most compelling
advantages of FPDs are instant manufacturing turnaround, low start-up costs, low financial
risk and (since programming is done by the end user) ease of design changes.