A Fresh New Look for Microcontrollers and their Memory Architectures

April 19, 2019

Connected ‘things’ are entering every aspect of our lives. Within these things – such as wearables, home monitoring nodes and industrial controllers – tiny embedded processors enable advanced functionality in form factors and power envelopes that are increasingly constrained. At the same time, many embedded applications require connectivity stacks, audio processing, and vision processing, as well as AI and machine learning algorithms. The amount of executable code for these functions has grown to substantial sizes.

This presents a challenge for designers of edge devices: how can they architect a system that achieves the needed performance and memory space needed to execute that considerable amount of code within extremely low power and area envelopes?

Many MCU vendors are looking at new architectures to address evolving computation needs. One example is NXP’s i.MX RT series of ‘Crossover Processors’ which combine the higher CPU speeds, multimedia interfaces and expandable memory of an applications processor into an MCU form factor designed for low cost and fast development time.

One particularly interesting thing about NXP’s crossover processors is that they don’t include internal flash memory; instead they rely on external flash, enabling them to support any size of code and data memory space, as required by the application. This design flexibility is one of several advantages that this architecture brings. The removal of internal flash also allows the processor to be designed with a more optimized process node supporting higher speeds. It also lowers the processor cost and the BOM in general. Code can be executed directly from external flash. This is called eXecute in Place, or XiP. XiP enables fast boot and wakeup from sleep mode as code and data are available instantly and do not need to be copied to RAM. This of course also saves power. And by taking advantage of the processor’s instruction/data caches XiP is guaranteed to deliver very good performance not much below the performance one would get from using internal RAM. By considering XiP from the start of the chip design process, engineers can build a system designed for memory expansion – providing the scalability needed to support next-generation connected applications.

Advancements in companion serial NOR flash memory architectures, with enhanced capabilities to address cost, power, performance and security challenges, make XiP operation a no-brainer for storing and executing software for ever-growing embedded applications. Adesto’s EcoXiP™ Octal flash memory provides high performance and low power consumption, allowing even time critical software to be executed directly out of non-volatile memory, reducing boot time and system cost. EcoXiP features an octal flash interface and double data rate (DDR) so when the processor has a cache miss and must access external flash it can quickly fill in the cache lines reducing the latency to a minimum and keeping the throughput high.

In the semiconductor industry, thousands of capable microcontrollers are already integrating the type of memory controller needed to support XiP capability from serial NOR flash. Together, the right serial flash memory coupled with a capable processor can provide the right performance, security, power consumption and development experience.

The combination of EcoXiP and the i.MX RT1050 crossover processor provide the embedded platform needed to conquer the challenges of future embedded design. Together with NXP, we’ve developed a whitepaper that provides an overview of how performance and usability are addressed for systems depending on external memory.

You can download that paper here.

Want to try out the combination of Adesto’s EcoXiP and NXP’s i.MX RT series of crossover processors? We provide Evaluation Kits (EVKs) featuring EcoXiP Octal flash paired with NXP’s high-performance i.MX RT1050 crossover processors The EcoXiP EVK can be purchased from your local Adesto distributor, or you can contact Adesto directly at ecoxip@adestotech.com.

If your performance requirements are more moderate, you should consider the EVK for the new cost-effective NXP i.MX RT1015, which features a Quad interface with Adesto’s 128Mbit, 133MHz Quad flash memory on-board.


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