title: Mifare Classic - Unknown Command
body: <p>I'm simulating a Mifare Classic (1K) tag, and following the o ISO/IEC 14443 Type A protocol.</p>
  
  <p>I could not found any information about what should be a proper response in case of receiving an unknown command from the reader (the reader supports other protocols).</p>
  
  <p>Should I respond with an invalid operation NAK? Should I just ignore the command?</p>