Recommendations when developing the M24LRxx application software

AN3057

10/15

Doc ID 16239 Rev 4

Important

It is paramount to exactly carry out the I²C polling sequence described in Figure 8 in order to

keep the M24LRxx in a constant I²C busy state.

●

Right method: once the device select is acknowledged, the I²C command starts

executing until full completion, that is, until the transmission of the Stop condition which

●

Wrong method: looping on the device select until it is acknowledged, sending a Stop

condition and then initiating a new I²C command: this is inadequate as an RF request

might have been served between [Ack] and the new I²C command (time slot during

which the M24LRxx is not in the I²C busy state.

Note:

If the application is disturbed by too great a number of decoded RF commands, it might be

convenient that the I²C bus master prompts the application to stop RF requests so that the

I²C bus can access the M24LRxx.

3.1.2

I²C requests and RF time slots

Application software management

In most cases, the application fully controls the I²C bus. On the other hand, it cannot always

predict RF commands. To have a robust application, the M24LRxx should be fully controlled

through the I²C bus, that is, the application master has to:

1.

determine when the I²C commands have to be transmitted

2.

determine the time slots during which RF transfers may be processed

The reason for this is that RF commands might not be properly transmitted (for example, if

the M24LRxx leaves the RF field). The I²C bus Master has to prevent this from happening by

applying the following rules:

●

The Master determines when the I²C commands have to be transmitted

pin only when an I²C data transfer is under way

●

The Master determines the RF time slots

completion of the I²C data transfer. RF transfers are processed more safely when the

–

If the decoded RF command is correct, it is executed (no need to supply power

–

If the RF command is truncated (M24LRxx is outside the RF field), the M24LRxx is

reset (Power-off state, see Figure 9).