When I do an updateBinary on a ST25TA I get return of f2 2 or f2 3 What is that, it's not quite a WTX, and not quite a deselect?

[LAnse]

This is the same question that I posted on the NXP Community "Problems doing updateBinary"

I send 16 bytes using the NDEF updateBinary command after the NDEF Select file

0x2 0x0 0xd6 0x0 0x4 0x10 0x54, 0x77 0x61 0x73 0x62 0x72 0x69 0x6c 0x6c 0x69, 0x67 0x61 0x6e 0x64 0x74 0x68 

And get back 0xf2, 0x2

[Thomas Q.]

Hello,

The 0xF2 0x02 byte sequence is a valid S(WTX) response frame.

As depicted in table 20 of the datasheet of the ST25TA02KB product [1] :

• 0xF2 : S(WTX) without the DID field
• 0x02 : WTX=2, meaning an extended response delay of 2*FWT is requested by the tag,

FWT being the response delay coded by FWI in the ATS frame (see table 57)

Best regards,

NFC product support

[1] : https://www.st.com/resource/en/datasheet/st25ta02kb.pdf

[LAnse]

Hi Thomas,

Thanks for your answer! What I don't understand is that the payload is described in Table 21, and the two high bits b7 and b6 are shown as b11, so how can that byte be a 2?

Thanks,

Larry

[Thomas Q. · Accepted solution]

Hi Larry,

Table 21 of the datasheet describes the bit fields of the first byte of an S-block frame.

In your case :

0xF2 (hexa) -> 0b11110010 (binary) -> b7=1 b6=1 b5=1 b4=1 b3=0 b2=0 b1=1 b0=1

According to the table, this corresponds to a S(WTX) block with the DID field not present.

Regards,

TQ

[LAnse]

That looks right, you're a rock star! Thank you