Thanks for reply,

The datasheet of 89E564RD says that it is pin to pin compatible, software compatible, development tool compatible with 89C58.

This is a 51 derivative. The SFR are different but they are by default initialized to zero so that it is compatible with 89C58.

I have even tried the manufacturer's web site and done the necessary modification in my source file accordingly to make it 89C58 with 64 program memory.

What else i should try.

Regards,
kapil chaturvedi