Energy-efficient processing

Sensors embedded within cars could run for decades without failing, using a low-power 32-bit processor unveiled by ARM on 23 February.

The company has already sold the licence for the Cortex-M0 processor to two companies: Triad Semiconductor and NXP Semiconductors. Dominic Pajak, product manager at ARM, said that his company designed Cortex-M0 to be a more energy-efficient alternative to 8-bit- or 16-bit-based processors.

The device consumes only 85µW of power when using ARM’s patented cell library, yet it is able to perform computations four times faster than an 8-bit processor. It is expected that this will support the drive to meet low-power microcontroller connectivity demands such as USB, ZigBee and Bluetooth, without having an impact on energy efficiency or code size.

Pajak added that the processor is also extremely small and fits all necessary memory into the same space taken by a 16-bit microcontroller.

ARM hopes that its processor will open the door to an array of low-power microcontroller applications in areas such as medical devices, gaming accessories, e-metering and wireless personal area networks. The Cortex-M0 is also believed to have potential use in devices such as intelligent sensors and actuators, where data must be captured in analogue and transmitted digitally to another device.

Geoff Lees, vice-president and general manager of the microcontroller division at NXP Semiconductors, said that many of these applications currently use only 8- or 16-bit processors. The limited processing capability restricts the functionality of these devices.

‘Eight-bit processors are pretty much only effective at controlling indicators and switches and panel controls and they are not very good at giving a rich user experience such as graphics or touch screen,’ he added. ‘The Cortex-M0 will allow embedded designers to use 32-bit processing in areas where they formally couldn’t because of cost and power constraints.’

The Cortex-M0 is in the same family of processors as the Cortex-M3, which has been employed in applications such as industrial control systems and wireless networking, including ethernet.

It does not come with all the functionality of the Cortex-M3, but it does cost less. This is mainly owing to the simplified architecture of the Cortex-M0, which is easier to manufacture. It is predicted that the end cost of the Cortex-M0 would be comparable to that of an 8-bit processor.

With the success of Cortex-M0, Pajak said that there is nothing technically stopping the design of an even more powerful processor. ‘However, I think 32-bit has hit the sweet spot for microcontroller-embedded applications,’ he said.

In the PC market, 64-bit computing has emerged because those machines must handle large amounts of applications and users must be able to load multiple types of code at any time. Embedded systems, on the other hand, tend to be more firmly specialised for certain functions.

Yet Lees noted that there could be a market for 64-bit processing for embedded systems.

‘This might happen in the distant future as desktop technology migrates toward embedded space, but it is not really a current trend,’ he said.

Siobhan Wagner