From an old Loughborough Elec Eng student, if the swipe reader is anything like the type I use at work, you can connect the clock line to one of the interrupts and then when you get an int, just read the data line.

Just make sure you only enable the int when you get a signal from the card detect line, this way you dont waste cpu time if any random signals occur.

Be aware though, you then have to decode the data, std track 2 is 5 bits the top bit is parity and the lower 4 are the data ie.

pdddd ......... pdddd

That is provided you swipe the card in the right direction... if you hold the card with the stripe facing upward and at the top, the data starts from the right hand side about 7.5mm in.

Steve Troup