AN4125

Recommendations when developing the M24LRxxE_R application software

Doc ID 023297 Rev 1

13/15

2.2

Issuing a command through the RF channel

Case 1: the M24LRxxE_R is processing an I²C command

If the M24LRxxE_R is processing a command from the I²C channel, no command issued on

the RF channel will be executed (the RF command will not provide any response) when the

M24LRxxE_R is I²C busy.

The application’s RF software should include an “I²C busy polling loop” (including a timeout

as there might not be a response) when issuing an RF command. In this way, the RF

command is always correctly executed once the I²C commands under execution are

completed.

Case 2: the M24LRxxE_R application is powered on

The first condition for a safe design of an M24LRxxE_R application is that all the sensitive

data stored in the M24LRxxE_R memory are protected with RF passwords, so that a

spurious RF command could not modify these data.

The second condition for a safe application design is that the application Master fully

supplied, and the RF field drops to zero while the M24LRxxE_R is decoding an RF

command, then the M24LRxxE_R is reset. This means that the Master has to supply the

the time (see Figure 10).

Depending on the application’s RF data transfer flow, it might also be wise to add a third

level of safety:

●

once an RF session (several commands) is completed, blindly send a Write-sector

Password command with a wrong password value: this will set the internal flag defining

the status of the presented password (flag set as “wrong password presented”).

Case 3: the M24LRxxE_R application is not powered

This is the typical case where the application is packed in a box (at the end of the production

line) and the data update is performed through RF.

The only condition for a safe application design is that the sensitive data stored in the

M24LRxxE_R memory are protected with RF passwords, so that a spurious RF command

could not modify these data.

Table 4.

Command processed

by the M24LRxxE_R

Device status

I²C command

I²C busy state

RF command

The M24LRxxE_R is fully dedicated to RF

commands