INTRODUCTION

Substituting external EEPROM with emulated EEPROM from the embedded-Flash of the Microcontroller is a complex development. This application note assumes that readers are already familiar with the techniques used to secure the content of evolutive information in external EEPROM of embedded applications.

This application note is organized in 3 parts:

– description of the differences between external EEPROMs and embedded-Flash,

– general description of EEPROM emulation concept,

– introduction to embedded application aspects.

Although this application note is focused and applicable to ST10F269, ST10F280, ST10F276 (and its derivatives: ST10F275, ST10F273, ST10F272, ST10F271), ST10F252 and ST10F296, most of its content is not dependent on the microcontroller.

Description

External EEPROMs are often used in automotive applications to store adaptative/evolutive data. On the other hand, the Microcontroller used in those systems, are more and more based on embedded-Flash.

The trend to continuously reduce the number of components is forcing designers to look to use Flash memory to emulate EEPROM.

This application note will explain the differences between external EEPROMs and embeddedFlash and will give advises on how to substitute external EEPROM to emulated-EEPROM using the on-chip Flash of ST10F2xx devices.

Although the concept is easy to explain and implement “as is”, there are some embedded aspects that have to be taken into account.

In this application note, the handling of embedded aspects to secure the content of an external EEPROM are assumed to be known by the reader. So, this document is focusing on the differences between EEPROMs and embedded-Flash.