Serial Smart Card Readers
It all depends on what type of smart card that you are trying to read.
Is it a  mifare card iso 14443 or ISO 7816 iso.  It should confrm to a standard of the card type (the beauty of standards)  The card is made up of different sectors that you can read and write to and a card identity number.  Some sectors are private and need an access code.  So if you have a card writer you can set these sectors as you wish and add your own access code.  A serial read of the card should send back the card number binary which then needs to be converted into hex or decimal.
If I have a 26bit card reader for a 32bit card then it will not read all of the bits of the card id.  Then also you will need to mask if the reader starts reading at the second bit and where it finishes. Does that make it a bit clearer.  Find what sort of card it is first then go from there. Good luck

Warren