Hi,
I have a device which contains a chip with some calibration/ID data. The contacts are standard 6 gold plated pads as smart cards (credit, SIM ...) have. After some theoretic preparation (wiki, this app note) I tried to read the chip. I decided it is a synchronous smart card chip and used two wire protocol described in the linked appnote (Section 2.1) and datasheets of devices mentioned here. But I got only partial success. The chip is communicating somehow but the results are not as expected. After reset the chip should output 4 bytes of Answer-To-Reset data and then its I/O pin should go high impedance. My chip spits 16 bytes of data instead, followed by 24 bytes of 0xFF (= high impedance), then it shows another 8 bytes of data and another 12 bytes of 0xFF. Total 60 bytes of data and it repeats them again and again as long as I supply clock pulses. When I try to send a command it ignores it and continues output the 60 byte sequence. When I pull the Reset HIGH the chip pulls the I/O pin LOW (so disabling any communication and so it cannot be 3-wire device) and the 60 byte sequence restarts from the first byte after releasing the Reset.
I exhausted my knowledge and Googling does not show any usable information.
Currently my guess it this is a "dumb card" disguised as a smart card. It is unable to do more than present data in its one time memory. But I did not find any such "industry standard" solution so I don't know if it is true. Maybe I am only using wrong protocol? Do you have some experience with this?
Thanks
It could be that the access to the smart card is encrypted or so, and unless you pley the right fiddle it behaves dumb, which is not that dumb after all. I have a tiny bit experience with smartcards in a far past and there were a lot of company specific protocols then. Expect that didn't change.