☛ Yes, port 0 can be used as input output port.

☛ Port 0 is an open drain unlike ports 2,3,4.

☛ To use it as input or output the 10k ohm pull-up resisters are connected to it externally.

☛ To make port 0 as input port it must be programmed by writing 1 to all bits.

Example:

MOV A,#0FFH

MOV P0,A