• Port 1 dedicated only for I/O interfacing when used as output port not needed to connect additional pull up register like port 0.

• It have provided internally pull up resistor the pin is pulles up or down through internal pull-up when we want to initialize as an output port.

• To use port-1 as input port 1 has to be written to the latch., Input mode when ‘1’ is written to the pin by the external device then it read fine. But when ‘0’ is written to the pin by the external device then the external source.

• Must sink current due to internal pull-up if the external device is not able to sink the current the pin voltage may rise leading to a possible.

• The internal FET pull up is used to help the port-1 to speed up when it is used as an output port the internal FET pull up has another FET that is in parallel to lower FET.

• FET is turned on for two clock periods when the transition on the pin is low to high arrangement provides low impedance path to the positive supply voltage.