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Nothing left to be invented in embedded control (Part 2)

Posted: 25 May 2015 ?? ?Print Version ?Bookmark and Share

Keywords:microcontroller? MCU? Flash? PWM? CMOS?

An example, borrowed once more from the intelligent power supply class of applications, would show a simple synchronous switching regulator (buck) topology implemented by directly connecting the output of a comparator (peak-current detect) to the COG module. (More on this in the next installment.)

In summary, the "whole" is now bigger than the sum of the parts we started with, and the number of possibilities has increased exponentially.

The programmable logic fallacy
At this point, pushing these concepts to an extreme, it would be tempting to deduce that we would be best served by a system where each module is divided into the smallest possible logical unit (gates) and, as in a CPLD or FPGA, we had the ability to design every single element of the solution from scratch, from the ground up. Unfortunately, despite much focus in the recent years, the cost and power-consumption limitations of solutions adopting such extreme approaches renders them prohibitively expensive; not to mention the complexity and cost of the tools required to handle their design.

Core independent peripherals and their combinations, on the contrary, can be mastered in minutes, and are found in the most inexpensive and extremely low power devices available today. They speak to the designers that have worked in the embedded-control space for decades, using a familiar language and paradigm.

But wait, there's more
The number of core independent peripherals has increased at a steady pace over the past couple of years. As it would be impossible to list them all in detail, I will instead refer the reader to the Microchip Web page dedicated to the subject, and will proceed to a brief introduction of only a small selection based on purely personal preference...

HLT
The Hardware Limit Timer or HLT is essentially a re-triggerable timer. It exposes to the CLC and other peripherals a reset input that allows the timer to be restarted automatically without CPU intervention. Further, it can produce a direct output (pin/flag/interrupt) upon expiration. The most common use is as a synchronous watchdog of sorts, or an automatic timeout for the activity of other peripherals.

CRC-SCAN
This Cyclic Redundancy Check module is defined to operate on configurable (up to 16bit) polynomials, to satisfy most CRC algorithm standards. It is designed to be used stand-alone or in combination with a flexible memory scanner to perform very fast Flash memory checks, during normal CPU operation with minimal or no impact on its performance. Its primary use is in safety applications to assure UL or ISO Class B certification, while greatly reducing the CPU workload, timing constraints and application code size.

ZCD
The Zero Cross Detect module offers a clever solution to the problem of monitoring the status of a power line, while completely removing the danger of substrate current injection. The result is external component reduction, along with maximum on-chip analogue signal chain performance and robustness. Typical applications are found in many low-cost appliances for sensing (safety) or phase-cutting (TRIAC) output control.

Angular timer
The Angular Timer offers the transparent conversion of angles (expressed in degrees) into a proportional time delay (clock cycles), based on a given periodic input. It relieves the CPU from the need to perform extensive math calculations (including multiplications and divisions in 16 or 32bit precision) reducing code size, removing look up tables, and simplifying the application. Typical applications include motor control and various phase-cutting (TRIAC) applications.

To infinity and beyond
As we have seen, the power of the core independent peripherals is multiplied when we connect them togethercomposing new, perhaps never before imagined, functional blocks that relieve the CPU from potentially large computational loads and real-time constraints.

In the next and last installment of this brief article series, we will explore a few more examples of core independent peripherals; combining their functionality with analogue peripherals to create new "intelligent" analogue solutions that achieve further simplification, along with reduced cost and power consumption.

About the author
Lucio Di Jasio is the EMEA Business Development Manager for Microchip Technology Inc. He has held various technical and marketing roles within the Company's 8, 16 and 32bit divisions for the past 20 years. As an opinionated and prolific technical author, Lucio has published numerous articles and several books on programming for embedded-control applications. Following his passion for flying, he has achieved both FAA and EASA private pilot licence certifications.


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