Hi Bruno,

your problem sounds interesting, so I have
try to solve it.

My answer:
Yes, you can make it with the 8051 and also in C.
It need 17µs to sample the bit and 50µs to execute
the interrupt (at 12MHz). This was many times shorter
than your requirements (50µs / 350 - 400µs)

My solution can you see at:
http://www.specs.de/~danni/temp/cardread.lst



Peter