I am using an 87C52 (which is an 80C31 with internal RAM). I am NOT USING any EXTERNAL RAM or EXTERNAL ROM and I am trying to use PORT0 as an I/O port. PORT0 is being pulled up thru 100k ohm resisters and I am reading switches and writing to relays through PORT0.

When I write to PORT0 (PORT0 = 0x55) and then read PORT0 (temp = PORT0) the value of PORT0 never changes from a value of 0xFF.

I have even tried writing to PORT2 but its value also never seems to change.