October 2012

Doc ID 16239 Rev 4

1/15

AN3057

Application note

How to manage simultaneous I²C and RF data transfers with

the M24LRxx-R and M24LRxxE-R devices

1

Introduction

The M24LRxx-R or M24LRxxE-R is an EEPROM device designed to be accessed via two

different interfaces: a wired I²C interface and a standard contactless ISO 15693 RFID

interface.

Figure 1.

Typical application of an M24LRxx-R or M24LRxxE-R dual interface EEPROM

ST has published various supporting application notes explaining how the RF interface

works and the basic principles of passive RFID technology. These documents are available

from: www.st.com/dualeeprom.

The possibility of using two different interfaces to control the dual-interface EEPROM implies

two host controllers: a microcontroller with an I²C bus and an ISO 15693 RFID reader. Due

to their nature, these two host controllers are not synchronized, which means that both

controllers might try to access the M24LRxx-R or M24LRxxE-R concurrently.

To manage this kind of situation, the M24LRxx-R or M24LRxxE-R has a built-in circuitry able

to handle possible concurrent communications and powering activities from the RF and I²C

sides.

This application note describes how the M24LRxx-R or M24LRxxE-R arbitration circuitry

operates.

Table 1 lists the products concerned by this application note.

Note:

The standard M24LRxx-R and energy-harvesting M24LRxxE-R devices will be referred to

as M24LRxx devices throughout the document.

Table 1.

Applicable products

Type

Applicable products

Dual interface EEPROMs

M24LRxx-R, M24LRxxE-R

SDA

SCL

M24LRxx

Application master

Application board

I²C bus

ISO 15693 RF

ISO 15693 RF

ai17547v2

www.st.com