STMicroelectronics STM32L5x2 microcontrollers

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STMicroelectronics’ ultralow-power STM32L5x2 microcontrollers (MCUs) are designed to emphasise security to ensure better protected IoT-connected applications.

Operating at clock frequencies to 110 MHz, the MCUs start from the Arm Cortex-M33 32-bit RISC core with Arm TrustZone hardware-based security. Trusted computing authenticates devices connected to a network by creating a protected execution environment for cyber protection and sensitive code (cryptography and key storage) that blocks attempts to corrupt devices or software. A second, independent execution environment allows for the running of untrusted code.

To this foundation, ST adds the freedom to include or exclude each I/O, peripheral or area of Flash or SRAM from TrustZone protection, allowing sensitive workloads to be fully isolated for maximum security. In addition, ST has engineered TrustZone to ensure support for secure boot, special read-out and write protection for integrated SRAM and Flash and cryptographic acceleration, including AES 128/256-bit key hardware acceleration, public key acceleration (PKA) and AES-128 On-The-Fly Decryption (OTFDEC), to protect external code or data. The STM32L5 also supports active tamper detection and secure firmware installation. With this attention to security, the STM32L5 has been certified to PSA Certified Level 2.

ST also adds techniques like adaptive voltage scaling, real-time acceleration, power gating and multiple reduced-power operating modes to enable the MCUs to deliver high performance and long run times, whether powered by coin cells or even through energy harvesting. In addition, an efficient switched-mode step-down regulator can be powered up or down on the fly to improve low power performance when the VDD voltage is high enough.

The MCUs offer 512 KB of dual-bank Flash that allows read-while-write operation to aid device management and the Flash ensures a high level of safety by supporting error correction code (ECC) with diagnostics. There is also a 256 KB SRAM and features to support high-speed external memory including single, dual, quad or octal SPI and Hyperbus Flash or SRAM, and an interface for SRAM, PSRAM, NOR, NAND or FRAM.

The series makes it easy for developers to build trusted PSA Certified devices based on the Arm Cortex-M33 processor, providing a robust and secure foundation for devices ranging from consumer products to industrial equipment. They are suitable for Industrial IoT applications — including metering, health (human or machine) monitoring and mobile point of sale — that require security, in a standard temperature grade (-40 to +85°C) for consumer and commercial applications or high-temperature grade (-40 to +125°C) for challenging environments.

For more information: https://blog.st.com/stm32l5-trustzone-security/.