I seems have a demo program of using the SED1335 chip with the 51MCU, I will check my CD to see it it still there.
Well if you are using the 51/52 port as I/O in I/O port mode ( not in data bus mode), try to put a 0FFH to the port before you try to get the input.
Good luck and best 73 from Li.

P.S. How can I send the file to you?
Or just post in here??