Mikel,

Where does your code reside?

The 80C52 has no user-accessible internal code space. Presumably your code resides in external memory. That does not mate-up logically with your assertion that nEA is tied to Vcc. If nEA is tied to Vcc, it will execute code from within its ROM, which you can't modify.

How is your system configured? Where does the code reside?

If you use external memory, nEA has to be tied to Vss. In that case, P0 and P2 are used to route data and addresses to the external memory, and unavailable for I/O.

RE