hi..... i am doing a password based door lock system using microcontroller..... i am using keypad of phone to enter password, i used cm8870 to decode dtmf signals into binary code.... once i switch on the power it is taking the values itself... i used the loop


again:mov a,P0
anl a,#0fh
cjne a,#0fh,next
sjmp again
next:.........
..............

but this loop is not working.... Port 0 is stored with the previous value.... how to make all bits of port 0 high????