MOV A,P1
LOOP: CJNE A,#01H,LOOP

will the above command will work if it is required to check Status of entire port...in above case if any bit of P1 goes high the instruction will move forward , if all bits are low it loop around CJNE Line.

Now if the above works how it is possible to find which bit is set ..but if the above does not works any command to check status of entire port and then selecting which bit is set or cleared.