Cortex-M23 and M33 Incorporate Latest TrustZone Features

Oct. 27, 2016

ARM’s latest Cortex-M platforms using the ARMv8-M architecture are out. They include the Cortex-M23 and Cortex-M33 families.

William G. Wong

Electronicdesign Com Sites Electronicdesign com Files Uploads 2016 10 26 Cortex M33 Fig 1

1. The ARMv8-M TrustZone supports provides secure code and peripheral execution environments.

ARM’s latest Cortex-M platforms using the ARMv8-M architecture are out. They include the Cortex-M23 and Cortex-M33 families, and they specifically target applications for the Internet of Things (IoT). One of the main features of the ARMv8-M architecture is the ARM TrustZone security support (Fig. 1) with its secure and non-secure states.

The Cortex-M23 targets the same space as the Cortex-M0+ very-small, ultra-low-power systems, while the Cortex-M33 targets the higher-end Cortex-M3 space. A platform for the higher-end Cortex-M7 is likely in the works, although the Cortex-M33 has floating point support.

The two platforms share a number of features, including the new instruction set support for TrustZone that is integrated with the new memory protection unit (MPU). The MPU provides 16 isolation regions that can be shared among applications. The region protection extends to peripherals. Features from the ARMv7-M include enhanced conditional compare and branch instructions, as well as immediate move instructions. There is also improved atomic support for C11/C++11 load-acquire and load-release instructions for more efficient semaphore handling.

Electronicdesign Com Sites Electronicdesign com Files Uploads 2016 10 26 Cortex M33 Fig 2

2. The Cortex-M33 adds features such as a three-stage pipeline and an FPU.

The platforms differ in implementation, with a two-stage pipeline for the Cortex-M23 and a three-stage pipeline for the Cortex-M33. This provides the Cortex-M33 with more performance. The Cortex-M33 has additional options, such as a floating point unit (FPU) and DSP instructions (Fig. 2).

Chips based on the Cortex-M23 and Cortex-M33 are still in the works, but turnover to sampling products from ARM licensees is expected to be early next year.

About the Author

William G. Wong | Senior Content Director - Electronic Design and Microwaves & RF

I am Editor of Electronic Design focusing on embedded, software, and systems. As Senior Content Director, I also manage Microwaves & RF and I work with a great team of editors to provide engineers, programmers, developers and technical managers with interesting and useful articles and videos on a regular basis. Check out our free newsletters to see the latest content.

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I earned a Bachelor of Electrical Engineering at the Georgia Institute of Technology and a Masters in Computer Science from Rutgers University. I still do a bit of programming using everything from C and C++ to Rust and Ada/SPARK. I do a bit of PHP programming for Drupal websites. I have posted a few Drupal modules.

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