AN3057

RF - I²C arbitration mechanism description

Doc ID 16239 Rev 4

5/15

2

RF - I²C arbitration mechanism description

The M24LRxx arbitration circuitry is twofold. It contains:

●

a power management unit that handles the power coming potentially from the RF or the

I²C side

●

a communication arbitration unit that tackles potential concurrent communications from

the RF and the I²C sides

2.1

Communications and power supply conditions

The power supply management unit has been designed to allow for flexibility, especially

when both the RF power and the wired power line are active at the same time.

The basic principle is:

●

When supplied only from the RF side:

–

the M24LRxx can be accessed only by the RF reader

●

–

the M24LRxx will serve the first decoded command (either RF or I²C) and will not

decode any command from the other interface (either I²C or RF) until the first

decoded command is complete.

Table 2.

Four possible combinations of power supply sources

Possible

cases

RF field

Actions

Case 1

0 V or not

connected

Off

The M24LRxx is reset.

Case 2

0 V or not

connected

On

RF data transfers: yes

I²C data transfers: no

Case 3

1.

full details.

On

RF data transfers: yes

I²C data transfers: yes

(see Section 2.2: Communication

arbitration when the RF and I²C channels

are both active for details).

Case 4

On(1)

Off

RF data transfers: no

I²C data transfers: yes