Arm Introduces Cortex-M55 MCU Core, Arm Ethos-U55 microNPU for Cortex-M Microcontrollers

Artificial Intelligence and the Internet of Things often go hand in hand with AIoT being a new buzz word that came up last year or so. But for AIoT to scale we need ultra-low-cost, low-power solutions capable of doing inference at the sensor node level, and this is only possible with microcontrollers.

To achieve this goal, Arm has just unveiled the Arm Cortex-M55 microcontroller core optimized for artificial intelligence workloads that delivers up to a 15x uplift in ML performance and a 5x uplift in DSP performance with greater efficiency, as well as Ethos-U55 microNPU designed for Cortex-M microcontrollers that need even more AI performance (up to 480 times faster), while consuming as little power as possible.

Arm Cortex-M55

Key features and specifications:

Architecture – Armv8.1-M
Bus interface – AMBA 5 AXI5 64-bit master (compatible to AXI4 IPs)
Pipeline – 4-stage (for main integer pipeline)
Security – Arm TrustZone technology (optional)
DSP extension – 32-bit DSP/SIMD extension
M-Profile Vector Extension (MVE) – Helium (optional)
Optional Floating-point Unit (FPU)
Coprocessor interface – 64-bit (optional)
Instruction cache – Up to 64KB with ECC (optional)
Data cache – Up to 64KB with ECC (optional)
Instruction TCM (ITCM) – Up to 16MB with ECC (optional)
Data TCM (DTCM) – Up to 16MB with ECC (optional)
Interrupts – Up to 480 interrupts + Non-maskable interrupt (NMI)
Wake-up Interrupt Controller (WIC) – Internal and/or external (optional)
Multiply-accumulate (MAC) / cycle – Up to: 2 x 32-bit MACs/cycle, 4 x 16-bit MACs/cycle, 8 x 8-bit MACs/cycle
Sleep modes – Multiple power domains, Sleep modes (sleep and deep sleep), Sleep-on-exit, Optional retention support for memories and logic
Debug – Hardware and software breakpoints, Performance Monitoring Unit (PMU)
Trace – Optional Instruction trace with Embedded Trace Macrocell (ETM), Data Trace (DWT) (selective data-trace), and Instrumentation Trace (ITM) (software trace)
Arm Custom Instructions – Optional (available in 2021)
Robustness – ECC on instruction cache, data cache, instruction TCM, data TCM (optional); Bus interface protection (optional); PMC-100 (Programmable MBIST Controller, optional); Reliability, availability, and serviceability (RAS) extension

The faster ML performance is due to Helium technology and corresponding M-Profile Vector Extension (MVE) that were announced by Arm and covered on CNX Software in February 2019. Arm Cortex-M55 is just the first core to leverage the technology.

Arm Ethos-U55 microNPU

Arm Cortex-M55 cores and future compatible Cortex-M cores can be further extended with Ethos U55 microNPU with the following key features:

Performance (At 1 GHz) – 64 to 512 GOP/s
MACs (8×8) – 32, 64, 128, 256
Utilization on popular networks – Up to 85%
Data Types – Int-8 and Int-16
Network Support – CNN and RNN/LSTM
Winograd Support – No
Sparsity – Yes
Memory System
- Internal SRAM – 18 to 50 KB
- External on Chip SRAM – KB to Multi-MB
Compression – Weights only
Memory Optimizations – Extended compression, layer/operator fusion
Debug and Profile – Layer-by-layer visibility with PMUs
Evaluation and Early Prototyping – Performance Model, Cycle Accurate Model, or FPGA evaluations

Arm Ethos-U55 microNPU is compatible with TensorFlow Lite Micro framework and works on bare-metal Cortex-M55 platforms or ones running an RTOS. Arm provides several software components for the new IP including a TensorFlow Lite Micro runtime, CMSIS-NN, Optimizer, and a driver.

IoT platform Corstone-300

Arm also provides Corstone-300 reference design to let chip designers quickly get started with designs based on Cortex-M55 core(s) and Ethos-U55 microNPU. The platform comes with development tools such as CMSIS Software Packs, Trusted Firmware-M for security, RTOS Support (RTX, FreeRTOS, Zephyr OS and Mbed OS), Arm Development Studio based on Keil MDK, FPGA images, and fixed virtual platforms.

You’ll find more information in the announcement, and respective product pages for Arm Cortex-M55 and Arm Ethos-U55 here and there.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.