31 October 2006

Low-end Applications Demand 32-bit Processors

By Haydn Povey
The microcontroller landscape is undergoing a pronounced transformation.

While volume shipments of 8-bit microcontrollers are currently 7x those of their 32-bit counterparts, their growth rate is the complete reverse, with 32-bit microcontroller shipments growing 100x faster than 8-bit, according to industry estimates.

There are a number of solid business and technology trends driving this migration. Even applications that appear to be ‘low-end’ now demand more sophisticated processing, and can benefit from the additional performance delivered by the 32-bit processor architecture. Take the classic white goods product – the humble washing machine.

Government regulations and consumer demand for better energy and water utilization from a wash cycle now require a more efficient way of controlling the motor. The design of efficient fractional horsepower motor drives, which employ techniques such as pulse width modulation, presents some interesting technical challenges that require advanced algorithms to be implemented. These challenges are well beyond the capabilities of the 8-bit microcontroller, and often require a full 32-bit microcontroller such as those based on the ARM Cortex™-M3 processor which delivers 10-15x the performance per megahertz of an 8-bit 8051 device.

Future Application Trends
Looking into the future, a growing trend to simplify user interaction with appliances will further increase processing demands. Once again, the washing machine provides a graphic example. Faced with a confusing selection of 30 or more wash cycle options on the average washing machine, in practice most consumers limit their choice to just one or two familiar programs. The way forward is for the appliance itself to choose the best program. By sensing the weight of the load, temperature of the water, amount of dirt and so on, the intelligent machine will deliver the best results with the minimum use of energy, water and user intervention. This level of intelligence requires even more intensive computation from the processor.

Accompanying this trend toward more advanced processing, pervasive communication is placing further demands on microcontroller performance. Protocols such as integrated Ethernet, USB, ZigBee and Bluetooth are becoming routine additions to many products. What’s more, these trends span many application domains. From refrigeration to home automation, and automotive to industrial domains, processing demands are growing.

32-bit Production Cost Benefits
While the applications themselves are becoming more technically challenging to design and develop, it’s not all bad news for the manufacturers and designers.

Because a single 32-bit processor can perform the tasks of several 8-bit processors, many manufacturers are taking advantage of the opportunity to aggregate several 8-bit devices into one 32-bit processor. This brings two major benefits: a simplified development process and reduced production costs.

Cost has been a barrier to the adoption of 32-bit processors in the past. There are two main cost components: the development (or NRE) costs and the unit volume costs. In 2006, the cost of an 8-bit microcontroller varies somewhere between 30 cents and $7, with an average selling price of around $3.50. By way of comparison, devices based on ARM’s 32-bit Cortex-M3 processors can be purchased for as little as $1 in volume, and ARM7 processor-based implementations can be sourced from around $1.50.

As discrete devices, most processors are pad-limited – in other words the opportunity to shrink the die is constrained by the need to fit the bonding pads around the perimeter of the chip. As minimizing the size of the die is not a priority, microcontroller manufacturers will typically target previous-generation processes such as 0.25um and 0.18um, where the process development costs have already been amortized and the cost of mask sets is considerably reduced compared with the latest state of the art 90nm and 65nm processes. Today, unit volume cost is therefore much less of a barrier to designing with 32-bit processors.

Controlling Development Costs
With regard to development costs, design teams are experiencing a raft of benefits from the move to the 32-bit architecture. There are few standards in the 8-bit microcontroller world, which has led to a proliferation of different development platforms and tools. It’s not unusual for a single company to be burdened with maintaining an array of different tool chains depending on which 8- and 16-bit devices they support.

This severely constrains the opportunity for code re-use, and significantly increases overheads for tool chain maintenance and their engineer’s training requirements, whereas for 32-bit ARM devices it is possible to support multiple vendors’ devices, and easily port code between them, in a single IDE, such as the ARM RealView Microcontroller Development Kit or IAR Electronic Workbench.

Additionally, while programming 8-bit devices often still relies on writing the application in assembly code, 32-bit platforms are much more amenable to taking a high-level approach to code development, whether in ‘C’, UML or from a high-level tool such as MathWork’s Simulink. This means that the platform approach can often be taken, where an application can be developed once and re-targeted multiple times.

ARM Defines 32-bit
With application processing demands up and volume production costs down, there is an unmistakable migration to 32-bit processor architectures, even for product applications that have previously been tagged as ‘low-end’. Increased functionality and integration is driving the move from traditional 8-bit microcontrollers toward the greater performance and flexibility provided by cost-effective 32-bit designs.

Standardizing on a processor architecture and peripherals will help to manage the complexity, connectivity and compatibility of systems whilst decreasing the resource requirements during the development cycle.

ARM’s industry-leading 16/32-bit architecture is forward-compatible and protects investment in hardware and software. Most of the world’s leading microcontroller suppliers now provide ARM processor-based microcontroller products, offering a broad choice of manufacturing sources. The ARM Connected Community also offers a broad choice of application-specific intellectual property, operating systems and development environments from over 400 partners, making it the best supported microprocessor architecture available.