Recommendations when developing the M24LRxxE_R application software

AN4125

10/15

Doc ID 023297 Rev 1

Important

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

keep the M24LRxxE_R 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 M24LRxxE_R 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 M24LRxxE_R.

2.1.2

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 M24LRxxE_R should be fullly

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 M24LRxxE_R 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

The Master delivers the supply voltage (through one of its I/Os) to the M24LRxxE_R’s

●

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 (M24LRxxE_R is outside the RF field), the

M24LRxxE_R is reset (Power-off state, see Figure 9).