Hi,
My company uses mifare classic 1k acces cards. I want to implant a chip in my hand to open the door. Is the xNT chip ’ backward’ compatible and can I use the xNT chip or do i need the the xM1chip as this is based on the mifare classic?
Best ragrds,
Jeroen
Compatibility is a strange beast. It really depends on how your access control system utilizes the Mifare “classic” chip and its features. If the system writes data to memory blocks and/or leverages the access bits in any of the the security (crypto1) sectors of the classic tag, then the NTAG216 won’t work for this because the NTAG’s memory structure and feature set are nothing like the “classic” mifare tags.
But, both classic and NTAG chips are ISO14443A and both work approximately the same way when spitting out their UID serial numbers, so if your system just relies on the tag or card’s UID and nothing more, then it might work. The problem is that NTAG chips have a 7 byte UID and “real” classic mifare cards (the old ones) only have a 4 byte NUID or Non-Unique IDentifier, which they had to change once they ran out of IDs and cycled back around to 0x00 0x00 0x00 0x01 
… so, if a system that expects a 4 byte ID gets a 7 byte ID, two things may happen… first, no workies. Second, you get a truncated ID (either the first 4 bytes or the last 4 bytes are all that are used). That means it could still work, but it also means that there is a huge chance for collision, especially among other xNTs since we bought serialized die cut wafer chips.
You might also want to read a bit about cloning because I talk a bit more about UIDs there.
That sounds like al long shot, so I guess my best change is to wait for the xM1 to get released. Is there a rough estimation when this will be?
Probably 30ish or so days from now.