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November 13, 2018
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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?

  • November 13, 2018
  • 4 replies
  • 1044 views

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

    This topic has been closed for replies.
    Best answer by Thomas Q.

    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

    4 replies

    Thomas Q.
    Thomas Q.
    ST Employee
    November 15, 2018

    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
    LAnseAuthor
    Associate
    November 15, 2018

    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.
    Thomas Q.Best answer
    ST Employee
    November 16, 2018

    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
    LAnseAuthor
    Associate
    November 16, 2018

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

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