title: NFC tag user memory binary
body: <p>I'm trying to read NDEF records out of some NTAG213 &amp; NTAG216 NFC tags, and I seem to be getting some extra bytes in the user memory i'm not expecting.</p>
  
  <p>Based on the <a href="https://www.nxp.com/docs/en/data-sheet/NTAG213_215_216.pdf" rel="nofollow noreferrer">spec</a>, the user memory should start from block 4, but when I read from the NTAG213 tags, i see 7 extra bytes before the NDEF record start, and 2 extra bytes for the NTAG216 tags.</p>
  
  <p>Here's the example of the NTAG213 memory:</p>
  
  <pre><code>01| 04 ae f4 d6 
  02| 0a d7 49 80 
  03| 14 48 00 00 
  04| e1 10 6d 00
  05| 03 db 91 01 &lt;-- NDEF starts at 91?
  06| 1a 54 02 65 
  07| 6e 43 4f 43 
  08| 4f 4e 55 54 
  09| 20 42 4f 44 
  10| 59 20 4d 49
  11| ...
  </code></pre>
  
  <p>The NDEF record appears to start with the header byte (91) in block 05, rather than the start on block 04.</p>
  
  <p>Does anyone know what the extra bytes are for, or how I can tell what the offset should be for reading back just the NDEF data?</p>
  
  <p>The bytes look a bit like some of the "Memory content at delivery".  But i'm not sure what the purpose is.</p>