This may be old information to you, but unlike a PIC whose ports default to inputs, the 8051 I/O pins default as outputs and need to be initialized to be used as inputs. Here is a paper that discuss the process: http://www.edsim51.com/8051Notes/8051/p … Ouput.html. If you still are having problems, I might be able to power up a 89C52 board that I have and give it a whirl. It depends on how busy I get over the weekend.