Introduction

For designers of STM32 microcontroller applications, being able to replace one microcontroller type with another from the same

product family easily is an important asset. Migrating an application to a different microcontroller is often needed when product

requirements grow, putting extra demands on memory size, or increasing the number of I/Os. The cost reduction objectives may

also be an argument to switch to smaller components and shrink the PCB area.

This application note analyzes the steps required to migrate an existing design from the STM32L1 series to the STM32U0

series. Three aspects need to be considered for the migration: hardware, peripherals, and firmware.

This document lists the full set of features available for the STM32L1 series and the equivalent features on the STM32U0 series

(some products may have fewer features depending on their part number).

To benefit fully from this application note, the user must be familiar with the STM32 microcontroller documentation available on

www.st.com, with a particular focus on the documents listed below:

• STM32L1 series datasheets.

• STM32U0 series datasheets.

•

STM32L100xx, STM32L151xx, STM32L152xx and STM32L162xx advanced Arm

-based 32-bit MCUs reference manual

(RM0038).

• STM32U0xxx reference manual (RM0503).

Migrating from STM32L1 to STM32U0 MCUs

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Application note

AN6020 - Rev 1 - March 2024

For further information contact your local STMicroelectronics sales office.

www.st.com

1 STM32U0 series overview

The STM32U0 series devices are a perfect fit in terms of ultra-low power, performance, memory size, and

peripherals at a cost-effective price.

In particular, STM32U0 series devices offer higher frequency and performance operations than STM32L1 series

devices. The STM32U0 series features an Arm

Cortex

‑M0+ processor at 56 MHz, versus a Cortex

‑M3

processor at 32 MHz featured on the STM32L1 series. STM32U0 devices also feature optimized flash memory

access through the adaptive real-time memory accelerator (Chrom-ART Accelerator).

STM32U0 series MCUs increase the low-power efficiency in dynamic mode (μA/MHz), and reach a very low level

of static power consumption on the various available low-power modes.

The detailed list of available features and packages for each product is available in the respective datasheets.

STM32U0 series devices include a larger set of peripherals with advanced features compared to the STM32L1

series, such as:

• Touch sensing controller (TSC).

• Low-power universal asynchronous receiver transmitter (LPUART)

• Infrared interface (IRTIM).

• Low-power timer (LPTIM).

• Voltage reference buffer (VREFBUF).

• DMA request multiplexer (DMAMUX).

• Clock recovery system (CRS) for USB.

• SRAM1 size is different on the various STM32U0 devices:

– 32 Kbytes for STM32U0x3.

– 8 Kbytes for STM32U0x1.

• Additional SRAM2 with data preservation in Standby mode:

– 8 Kbytes for STM32U0x3.

– 4 Kbytes for STM32U0x1.

• Optimized power consumption and an enriched set of low-power modes.

This migration guide covers only the migration from the STM32L1 series to the STM32U0 series, and as a

consequence any new features present on the STM32U0 series but not already present on the STM32L1 series

are not covered by this document. Refer to the

STM32U0 reference manuals and datasheets for an exhaustive

picture.

Table 1. STM32U0 memory availability

Part number

Flash memory size SRAM1 SRAM2 Feature level

STM32U031x4 16 Kbytes

8 Kbytes 4 Kbytes -STM32U031x6 32 Kbytes

STM32U031x8 64 Kbytes

STM32U073x8

64 Kbytes

32 Kbytes 8 Kbytes

With LCD + USB.

STM32U083x8

STM32U073 with

crypto.

STM32U073xB

128 Kbytes

With LCD + USB.

STM32U083xB

STM32U073 with

crypto.

STM32U073xC

256 Kbytes

With LCD + USB.

STM32U083xC

STM32U073 with

crypto.

Note: Arm is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.

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