So many microcontrollers…

Author : Andrea Riverso | Head of Product Management | Farnell

01 June 2019

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There are so many microcontrollers on the market today that it can be hard for electronics design engineers to decide which one to select for any given project. In part I of its focus on embedded system design, Andrea Riverso, Head of Product Management at electronic component & system distributor, Farnell reviews some of the hardware options available…

This article was originally featured in the June 2019 issue of EPDT magazine [read the digital issue]. Sign up to receive your own copy each month.

When evaluating the embedded microcontroller market, it would be very easy to think that the domination of Arm as the core architecture has allowed the market to stagnate – but, in fact, nothing could be further from the truth. The market remains buoyant, with a large number of new devices launched across a number of architectures.

Arm is certainly a firm favourite, especially within the 32-bit embedded market. This architecture is supported by more than 1,000 companies delivering silicon, development tools and software, and there have been more than 100 billion processors shipped that use the Arm architecture. Most of the leading microcontroller companies offer Arm-based microcontrollers or processors, but despite Arm’s strength, there are also great alternatives: the two most prominent being MIPS and RISC-V.

MIPS was one of the original RISC architectures spun out of Stanford University in the 80s. As one of the first processors of its time, MIPS had a major impact on the teaching of computer architecture.

RISC-V is relatively new, but is the leading open-source core, as a free and open instruction set architecture (ISA), and was designed to be used in modern computerised devices, such as warehouse-scale cloud computers, high-end mobile phones and the smallest embedded systems, all of which demand performance and power efficiency. RISC-V removes the need for expensive licences and gives flexibility to users.

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The wider market
Texas Instruments is an interesting case: not only does the company have Arm-based 32-bit microcontrollers, it also uses its own core called MSP430. MSP430 is designed for very low power consumption, making it a great option for applications such as process control systems, where this is important. In these applications, the individual sensor units must handle localised data analysis as well as communications. This has led to manufacturers including a microcontroller in the sensor node to enable these additional features.

Another popular 32-bit architecture that has been used in a range of embedded processors is the IBM Power Architecture. The most common use for this architecture is in data centre applications (IBM Servers, workstations, supercomputers) and embedded NXP processors, particularly for automotive, networking, consumer and industrial applications.

A primary driver of the cost of semiconductors is the area of silicon required, suggesting that more complex processors will be more expensive. As process geometries shrink, many microcontrollers are pad-limited. This makes the additional silicon area required for a 32-bit core less important, although smaller word-length processors are often manufactured in lower-cost process technologies than 32-bit devices can use.

Not just 32-bit
Most embedded applications find that 32-bit cores provide sufficient performance for their application requirements. So 64-bit processors tend only to be used in highly data or compute intensive systems. Such applications include those requiring real-time multitasking and higher processing power, such as computer-aided design, database management systems, and some technical and scientific projects. Both MIPS and Arm have 64-bit processor cores available.

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Going in the other direction, the use of 4-bit processors has decreased dramatically, with the most common use being in infrared remote controls and security alarms. There is still significant development of 8-bit processors, typically offering lower performance, but at a much lower cost than a 32-bit core. Additionally, it is possible to reduce power consumption in an 8-bit core, as fewer transistors need to switch because the word length is a quarter of the size of 32-bit cores.

Microchip is the leading 8-bit microcontroller provider, with both the PIC and the AVR architectures. AVR came from the Microchip acquisition of Atmel. Microchip has a portfolio of around 1,200 8-bit microcontrollers. The company’s technology uses core independent peripherals to handle repetitive embedded tasks, without taking resources from the core. This means that some of the 8-bit devices can outperform 32-bit microcontrollers when handling common tasks.

Some pundits have been predicting the death of the 8-bit market for many years, but in fact the opposite is true with more 8-bit devices going into designs than 32-bit products. Technology advances such as core independent peripherals have been a major factor in this.

Most of the microcontroller vendors offered by Farnell have an 8-bit architecture. It is clear that there remains a strong market for 8-bit where there is only a low performance requirement. This has meant that these devices have been able to take advantage of the growth in the internet of things (IoT) applications. Many of these so-called ‘things’ perform basic tasks, such as taking a measurement and sending the data on for processing. They only wake when needed and consume very little power – tasks that are highly suited to some of the latest 8-bit devices.

Specialist processors
Sometimes, processors need to deliver performance for specific applications. Digital signal processors (DSPs) are microprocessors that have a specialist architecture designed specifically to perform calculations. For computer-intensive applications, DSP solutions from Texas Instruments (TI) are very popular.

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Texas Instruments devices are suited to complex applications, such as machine vision commonly used in factory automation and robot guidance. DSPs allow the analytical processing of images, providing sight to otherwise blind equipment.

For applications using artificial intelligence (AI), specialist processors are often the best choice. Many semiconductor vendors have projects to develop processors designed to increase the performance of embedded applications, as well as dedicated libraries that support AI.

Conclusion
Although at first glance it may appear that the success of Arm has made the microcontroller industry less exciting, there is a huge amount of interest and investment in the development of microcontrollers and microprocessors, using a range of different cores, to meet the needs of growing markets such as IoT and AI.

With such a wide range of MPU and MCU options, many design engineers turn to specialist distributors such as Farnell for expert, device agnostic advice to guide them through the maze and suggest the ideal microprocessors, microcontrollers and development kits to help them complete their embedded designs.


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