XMOS Adds ARM to its Multicore Mix

24 October 2013

XMOS Ltd., a pioneer of C-programmable, event-driven, multicore processors has cut a deal with Silicon Laboratories Inc. allowing it to make use of Cortex-M3 based microcontroller die within its xCore architecture components.

The claimed benefit is that users can get the high peak performance—approximately 500-MIPS—and determinism of the xCore architecture while taking benefit of the extremely low standby current—of the order of 100nA—and embedded flash provided by the Gecko MCU. It also means that XMOS can run ARM code that is now standard in many microcontroller applications.

Nigel Toon, CEO of XMOS (Bristol, England), said that while he has been positioning XMOS as a microcontroller company it is impossible to ignore the strength of ARM and the presence of ARM code in the market.

The result is the XCore-XA—XA for extended architecture—allows system designers to use high-level C/C++ software to configure a device with the exact set of interfaces and peripherals needed for their design, while at the same time re-using existing ARM binary code and taking advantage of ultra-low energy peripherals. The multiple virtual xCore processors can run real-time and latency-critical data plane applications and DSP code with the ARM available to run control plane software and communication protocol stacks and standard graphics libraries.

XMOS has always provided a full-featured Eclipse-based integrated development environment (IDE) called xTimeComposer and that has been extended to include parallel panes for xCore and ARM code design entry, compilation and debug support. Developers can also make use of the xSoftIP library of software-defined digital peripherals.

The partnership deal was originally drawn up between XMOS and Energy Micro AS (Oslo, Norway), a developer of ARM-based microcontrollers with a reputation for extremely low power peripherals that are very efficient during wake up modes. Silicon Labs acquired Energy Micro in June.

The first device in the xCore-XA family features one xCore processor and one Cortex-M3 microcontroller on separate die. These are then organized as eight virtual 32-bit processors by time-slicing of resources (seven xCore logical cores plus one ARM processor), together with 192-kbytes of SRAM and 1-Mbyte of flash memory. The device includes a low energy USB interface, low-energy peripherals and analog functions, including ADC, DAC, op-amps and capacitive sensing comparators.

Criticism has been levelled at xCore devices in the past for a lack of memory. The inclusion of the Gecko MCU, which includes embedded flash, may go a little way to alleviating that but a significant change will probably necessitate a redesign of the xCore on 28-nm CMOS. The xCore digital die is currently implemented on 65-nm.

Toon said it was necessary to be pragmatic about the presence of ARM in the market and that many customers will ready putting XMOS processors down next to ARM microcontrollers. Not re-inventing the wheel and letting a Gecko MCU provide low-power wake up, control and basic functionality left the xCore free to do real-time computation for such applications as hazardous plant monitoring, medical equipment, multi-axis motion control and vision processing such as edge-detection and image recognition.

Toon positioned the xCore-XA as a lower cost and lower power alternative to FPGAs. The part is priced at $16.39 in low volumes. On the technical front ARM's own Cortex-R series of cores, also optimized for real-time, deterministic applications could also provide competition, although they are not generally offered in a "with-peripherals" microcontroller format.

ARM is supportive of the XMOS innovation, which will help ship more Gecko die, which means more royalties for ARM. "ARM believes that xCore-XA represents a significant step forward for embedded systems, allowing engineers to create an integrated SoC that is configured completely in high-level software. Xmos is the leader for this category of configurable multicore microcontrollers and Silicon Labs produces outstanding low-energy ARM Cortex-M3 technology. By combining these two powerful solutions, Xmos has created a new category of low energy, programmable SoC products," said Nandan Nayampally, vice president of application systems marketing at ARM.

One hope is that the xCore-XA could also play in automotive applications. "Our xCore range will receive automotive qualification this year and we are designed into 2015 automotive platforms. We don't have a time line for xCore-XA yet," Toon said.

In the future XMOS could provide components with increased real-time capability and Toon is not averse to including wireless transceivers to address machine-to-machine (M2M) and Internet of Things (IoT) applications. When asked if that would also be done through an extension of the deal with Silicon Labs, Toon said: "We're talking to some other people about wireless."

XMOS will be demonstrating xCORE-XA at the ARM TechCon conference in Santa Clara, Calif., Oct. 29 to 31. Engineering samples and initial development boards will be available to lead customers in November, with a full production ramp in the first quarter of next year.

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