Bench Talk

There’s an adage in writing—write about what you know. Well, I’m an engineer, so they asked me to write about engineering things.

Along with doing my duty by day as an engineer, I recently got called to do something else. I’ve been asked if I’m willing and able to teach a college philosophy course this spring on metaphysics and epistemology. But don’t worry! Besides my engineering degree, I also have a degree in philosophy, so I’ve seen these complicated words before. Metaphysics is the study of reality, and epistemology is the study of knowledge.

You, Me, and Aristotle: Knowledge and Logic

In preparation to teach this course, I must develop a syllabus and read books to refresh myself on these topics. In the world of metaphysics, one of the must-reads is a classic called Metaphysics (circa 350 BC) by Aristotle (384–322 BC). In it, Aristotle states: “All men naturally desire knowledge” (Book 1, Part 1, 980a.21).

In studying these subjects, one must study logic as well, so one can properly employ the methodology of reasoning well. Here again, Aristotle is helpful. I’ve been working my way through some of what he wrote in Organon (a Greek term meaning “organ,” “instrument,” or “tool”), where he lays out his influential understanding of logic as well as how to categorize.

There’s a good chance you’re not about to show up in my philosophy class this spring to learn more about Aristotle, knowledge, and logic. However, I suspect that if you’re like many other engineers, you may be interested in knowing more about the logic behind programmable solutions categorization and how to distinguish their specific classifications.

The Programmable Logic Device

A programmable logic device (PLD) is a circuit that a user can configure and reconfigure to perform a logic function. Vital to the world of technology today, PLDs find a host of applications in various industries and sectors including:

• Communications
• Data centers
• Industrial technology
• Automotive technology

Within electronic systems that employ PLDs, one will often find three key elements, which are:

• Microprocessors: to control and compute
• Memory: to store
• Logic: to manage and manipulate

Three Types of Programmable Logic Devices

Three types of devices are classified as PLDs. These include field-programmable gate arrays (FPGAs), complex programmable logic devices (CPLDs), and system-on-chip (SoC) field-programmable gate arrays (I find the latter is abbreviated in various ways, including SoC FPGA, programmable SoC, gate array SoC, gate array programmable SoC, or similar. You get the point!).

Let’s discuss the PLD with the complicated acronym first. In many cases, it’s desirable to combine the microprocessor functions within a single device. This is achieved by using a hard-embedded processor core—such as an Arm^® processor—and memory functions with programmable logic. Essentially, this is what a SoC FPGA is (Note: This my acronym of choice!).

While CPLDs and FPGAs are both classified as PLDs as well, they are also standard semiconductor integrated circuits (ICs)—or chips. CPLDs are suitable for small, uncomplicated, logical tasks—contrary to FPGAs—and are used in applications where glue logic—that is, custom logic circuitry—is needed to interface off-the-shelf ICs. CPLDs and FPGAs also differ in their internal architecture regarding how they perform their logical operations. CPLDs employ look-up tables (LUTs). In contrast, FPGAs utilize a sea-of-gates that are frequently exemplified as AND, NAND, OR, and NOR gate combinations.

In general, due to having a non-volatile configuration memory, CPLDs don’t need a flash each time they receive power—a feature many consider to be a security advantage. An example is the Intel^® MAX^® CPLD Series, which features up to 8Kbits of non-volatile storage for critical system information. In 2014, the introduction of Intel^® MAX^® 10 FPGA represented a leap forward in integration and FPGA capabilities.

The MAX^® 10 represented a new series of non-volatile programmable logic devices, displacing what was once the sole domain of the CPLD. This revolutionary single chip (with dual configuration) integrates flash, analog-to-digital converter (ADC), RAM, and digital signal processor (DSPs) functionality without needing external flash, and it operates at silicon speed—"instant-on.” Intel’s new approach to FPGA design has ushered in better design flexibility, lower bill of materials (BOM) costs, a lower printed circuit board (PCB) footprint, better system reliability, and greater design security.

FPGAs are designed to have high levels of complexity and a wide range of integration capability, while also being available for standard configurations and part numbers. FPGAs give engineers the flexibility to tailor their products and deliver them to market quickly. Upon a successful completion of design, FPGAs are suitable for volume production, because they are highly repeatable and much of the electrical functionality of the device is easy to change—primarily through software reprogramming. Relative to application-specific integrated circuits (ASICs) and application-specific standard parts (ASSPs), FPGAs offer lower upfront expenditures, a faster time to market, and increased design flexibility. Programmable solutions provide value to customers by way of lower costs and power use. Simultaneously, these solutions provide improved performance and density in designs that experience the continuous burden of increased complexity, reduced time to market, higher needs for customized solutions tailored to specific demands, and market pricing pressures.

With their stress-free capacity to expand input/output (I/O), FPGAs provide a cost-effective, application-specific peripheral set that delivers all the necessary interfaces. Their ability to be custom-tailored for a specific application yields improved performance—particularly, by maximizing the application’s performance per watt. FPGAs are very adaptable to change. This allows customers to have lower inventory risks, because they can always receive parts with the latest revision(s), which mitigates hardware obsolescence through product migration and updates.

Back to Aristotle

While Aristotle is long gone, his thoughts live on through his legacy of writings. He has helped to shape us from the past up to the present. I don’t know anywhere close to what Aristotle knew, but I do know one thing: You as a design engineer, and as a person, innately want to know and understand. You want what you design to be a logical extension of your ideas and thinking. Here’s to hoping that you use your mind to its fullest. If PLDs are one way to meet and enhance your designs, my desire is that you’re successful in using these logical devices without any creative limitations. After all, Aristotle believed that the excellent person will live a good life (Nicomachean Ethics). As an engineer, who am I to argue with kind of logical thinking!