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M251/M252 Series

NuMicro® M251/M252 Series Microcontroller

A Low Power 5V Microcontroller Based on Arm® Cortex®-M23 Core

The industrial-grade NuMicro M251 / M252 series designed for industrial control applications. It is based on Arm Cortex-M23 secure core for Armv8-M architecture, running up to 48 MHz with up to 256 KB Flash and up to 32 KB SRAM. The power consumption in the deep power-down mode is down to 2.0 μA; NuMicro M251/M252 Series provides five kinds of power modes and three kinds of secure protect mechanisms to satisfy the sensor node devices which cares power consumption in IIoT applications.


Package Available: TSSOP20 ( 4.4×6.5 mm ) , TSSOP28 ( 4.4×9.7 mm ) , QFN33 ( 5×5 mm ) , LQFP48 ( 7×7 mm ), LQFP64 ( 7×7 mm ), LQFP128 ( 14×14 mm )

Target Application: Smart Home / Smart Home Appliance, Industrial Control / Industrial Automation, Smart City, IoT Device, Security Alarm System, Electronic Payments, Communication Modules, Portable Wireless Data Collector, Smart Door lock, Handheld Medical Device, ( GPS ) Location Tracker, Electronic Shelf Labels ( ESL )


Low Power

Industrial-grade Low-power MCU

The wide supply voltage ranges from 1.75V to 5.5V and operating temperature ranges from -40℃ to 105℃, NuMicro M251/M252 Series provides a rich package types from 20 pin to 128 pin, and 5 power modes for different operating scenarios. Integrating RTC with independent VBAT to support low power mode, low power UART supports transmission rate up to 9600 bps in power-down mode to make power management much efficiently in battery-powered devices. In terms of low power consumption, NuMicro M251/252 Series provide 138 μA/MHz in normal run mode. Power-down mode current with RTC on is down to 2.5 μA and Deep power-down current is less than 1.4 μA.

Fit for Industrial Control

Nuvoton Patented “PSIO”

NuMicro M251/ M252 Series provides up to eight channels of Nuvoton Patented Programmable Serial I/O (PSIO), accompany with PDMA hardware could realize several proprietary serial interfaces, such as DMX512, HDQ, 1-wire, Microwire, and programmable encoder, no matter the standard interface or proprietary interface can be realized by PSIO interface, which can not only adding the feasibility of proprietary interface but also shorten the complexity of program but to ease the loading from CPU.

Powerful Interface

Powerful Interface

Up to six pins of Voltage Adjustable Interface (VAI), External Bus Interface (EBI), Universal Serial Control Interface (USCI), QSPI, SPI/I²S, I2C, Smart Card Interface (ISO-7816-3), Watchdog timer, RTC, and up to 24 channels of PWM are provided. Those peripherals make it highly suitable for connecting comprehensive external modules. For high performance analog features, it integrates up to a 16-channel 12-bit 880 kSPS SAR ADC to sample the sensor data without delay, one Operational Amplifier (OPA) to amplify small signal for motor control, built-in 5 levels of internal voltage reference to provide precise voltage to ADC and ACMP, one 12-bit 1 MSPS voltage type DAC, and two rail-to-rail analog comparator (ACMP) to enhance product competitivity and reduce both external components and form factor.
 Chip Security  

Chip Security

To protect customer’s intellectual property, NuMicro M251/M252 Series provides several mechanisms, by using flash lock bit can prevent program from being read out by external programmer, built-in one eXecute-Only-Memory (XOM) region and four Memory Protection Unit (MPU) to protect critical codes, and one Tamper detection pin to detect the state transition status. NuMicro M251/M252 Series also equipped with 96-bit UID ( Unique Identification ) and 128-bit UCID ( Unique Customer Identification ).  Besides, Nuvoton provides safety library which can compliant with IEC-60730 requirement for Class B safety function to raise safety function for customers’ end products.

Target Application


Target Application

NuMicro M251/M252 series fits the low-power devices in the Industrial internet of things (IIoT) application. Firstly, the whole series supports 5V operating voltage and high immunity performance with 7KV ESD and 4.4KV EFT. Besides, NuMicro M251/M252 series offers five different power modes to extend the battery life of the IoT devices. Furthermore, there are three types of chip protection mechanism and rich periphiral to connect multiple sensors, which beneficial of IoT application.
Development Platform  

Development Platform

Moreover, Nu-Link and Nu-Link-2-Pro debuggers are available for evaluation and product development. Third-Party IDEs such as Arm Keil MDK (free-to-use of NuMicro M23-based project), IAR EWARM, and NuEclipse IDE with GNU GCC compilers are also supported. The latest NuTool-Code-Generator is available to generate the initial program automatically.


M251/M252 Development Platform

IC M251/M252 Datasheet
M251/M252 Technical Reference Manual (TRM)


Product Introduction
Technical Features:
M23 Core Efficiency
Programmable Serial I/O (PSIO)
Power Mode
XOM Operation
M251 Series
M252 Series
Hardware Development  - Hardware Introduction
Design Guide - ETT
Design Guide - USB Layout Guidelines
Design Guide - Crystal
Development Tool NuMaker-M251KG User Manual
NuMaker-M251SD User Manual
NuMaker-M252KG User Manual
NuMaker-M252SD User Manual
NuMaker-M251KG Quick Start
NuMaker-M251SD Quick Start
NuMaker-M252KG Quick Start
NuMaker-M252SD Quick Start
Quick Start a NuProject:
How to Download and Install KEIL
How to Download&Install Nu-Link KEIL Driver
Board Support Package
Debugging & Programming Nu-Link2-Pro User Manual
Nu-Link Driver for IAR User Manual
Nu-Link Driver for Keil MDK User Manual
Debugger & Programmer

NuLink-Gang/NuLink2-Pro & programming tool and usage scenarios
Features and Functions
In-Line Programming:
Drag and Drop Programming & In Circuit Programming
ISP (I2C Interface)
Off-Line Programming:
Using SPI Flash to Download Triggered by Control Bus
Through VCOM to Print UART Message on PC
Embedded Trace Macrocell (ETM)
Firmware Update:
Drag and Drop Programming & In Circuit Programming

Nuvoton Software Tool (NuTool) NuTool-CodeGenerater
NuTool NuTool-CodeGenerator
IDEs Keil MDK Nuvoton Edition *Free-to-use
IAR Embedded Workbench
NuEclipse (Windows Version) - within GNU Eclipse Framework
NuEclipse (Linux Version) - within GNU Eclipse Framework
IDEs & Nu-Link Driver    -


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