AN3057 Datasheet, PDF (1/15 Pages) STMicroelectronics – How to manage simultaneous

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
Application master
SDA
SCL
I²C bus
M24LRxx
IISSOO 1155669933 RRFF
Application board
ai17547v2
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.
Table 1. Applicable products
Type
Applicable products
Dual interface EEPROMs M24LRxx-R, M24LRxxE-R
Note:
The standard M24LRxx-R and energy-harvesting M24LRxxE-R devices will be referred to
as M24LRxx devices throughout the document.
October 2012
Doc ID 16239 Rev 4
1/15
www.st.com