P1 is a 8 - way 1/O port with internal pull ups, and the output of the P1 can be driven by the output buffer level (absorption or output current) 4 TL logic gates. Write to the port of.'1l., through the internal pull-up resistor pins theyarepulled high, this can be used as inputs. When used as inputs, because of the internal pullups, an externally being pulled low will source current (during 110.Flash programming and P1 receiving low 8 address