March 2009 Rev 1 1/36
AN2645
Application note
Migration and compatibility guidelines
for STM8S microcontroller applications
Introduction
For designers of STM8S microcontroller applications, it’s important to be able to easily
replace one microcontroller type by another one in the same product family. 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. On the other
hand, cost reduction objectives may force you to switch to smaller components and shrink
the PCB area. This application note is written to help you and analyze the steps you need to
migrate from an existing STM8S-based design to any one of the 20+ other microcontroller
types in the fast-growing STM8S family.
To save your time, this application note groups together all the most important information
and lists the vital aspects that you need to address.
All the information included here can also be extremely worthwhile in your first STM8
design, not immediately concerned by a migration project. Studying the issues now will help
you tackle any future requirement by designing for compatibility from the beginning. To use
this application note fully, general STM8S knowledge is required, you can learn it from the
STM8S family reference manual (RM0016), the STM8S datasheets, and the STM8S Flash
program memory / data EEPROM programming manual (PM0051).
This document is divided into three main sections:
● Section 1: STM8S family compatibility: This section presents a first level view of the
different aspects of the STM8S family architecture that are important to consider when
planning a new design or migrating. The microcontroller blocks and peripherals are
grouped and identified either as compatible or compatible with minor limitations.
● Section 2: Planning for migration: This section gives an overview of common
migration cases. It provides a checklist of items which are potentially impacted by each
case to allow you to quickly analyze which subjects you need to anticipate.
● Section 3: Block-by-block compatibility: This section lists all the topics for each
block, focussing on the compatibility aspects in more detail.
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Contents AN2645
2/36
Contents
1 STM8S family compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1 Family concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2 Fully compatible blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3 Blocks that are compatible with minor exceptions . . . . . . . . . . . . . . . . . . . 7
1.4 Blocks that are compatible with significant exceptions . . . . . . . . . . . . . . . . 8
2 Planning for migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Block-by-block compatibility analysis . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1 Package pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.1 Migration from one sub-family to another one . . . . . . . . . . . . . . . . . . . . 13
3.1.2 Migration to a package with different pin-count within the same sub-family
15
3.1.3 System pins and package pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.4 Digital power supply and package pinout . . . . . . . . . . . . . . . . . . . . . . . 20
3.1.5 ADC power supply and voltage reference in package pinout . . . . . . . . 20
3.1.6 Alternate functions and package pinout . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2 Digital I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.1 GPIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.2 High-sink capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2.3 External interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.3 Timers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.4 Analog-to-digital converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.4.1 ADC inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.4.2 ADC supply and reference pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.4.3 ADC modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.5 Communication peripherals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.5.1 SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.5.2 I2C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.5.3 CAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.5.4 UART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.6 Clock controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.6.1 HSE clock frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.6.2 HSI clock frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
