Hi ridvvan,

if port P2 oscillate crazy, it sounds, that the 8051 try to access external code memory.
The reasons can be:

1.
the EA pin was not connected to VCC

2.
no reset was done

3.
no program inside the 8051 (erased state)

4.
the program runs outside the internal code size, e.g. the main loop was not finished with a jump to the beginning



Peter