I/O

• Inputs: pins that are designed to receive data from an external source. Inputs do not drive a pin to either ground or Vcc.

• Outputs: pins that are designed to send data to an external part. To signal data the chip internally connects the pin to either ground (low) to signal a 0 or Vcc (high) (to signal a 1).

• Some pins are I/O pins and can operate in either mode. The mode is selected through software.