ST25R3916 - Auxiliary definition register - nfc_n<1:0>, value = 512, unit: /fc?

[ctee]

Hello,

 

I have a question on the value of nfc_n<1:0> of the Auxiliary definition register.

The following tables talk about the field value, could you please explain further what is the meaning

of the value 512 in Table 14?

Is my interpretation as shown below correct?

When fc = 13.56MHz, 1 unit of T_RFW = 512 / fc = 37.76us

If n = 1, Total RF waiting time = 37.76us

if n = 2, Total RF waiting time = 2 x 37.76us

if n = 3, Total RF waiting time = 3 x 37.76us

if my interpretaion is correct, what happen when  n = 0, can n be set = 0 before NFC field on?

 

Thanks!

 

BR,

ctee

 

[Ulysses HERNIOSUS]

Hi ctee,

nfc_n defines the timing used by the RF collision avoidance procedure - triggered either by direct command or automatically in case of AP2P with nfc_ar=1.

The time until the field on is: T_IDT + nfc_n*T_RFW.

Yes, also nfc_n=0 is a legitimate value for this formula.

I hope this clarifies this topic for you.

BR, Ulysses