Registers:
Enable Reg: enable the pin as a function or just a GPIO pin.
Direction Reg: I/O, input or output. (defined by hardware)
Output Reg: Activity, activize utility of the GPIO pin when high or low current. (0 or1)
Input Reg: The reg for input data. (device ==> cpu)
Input/Output:
Output: cpu ==> device (ex: led)
Input: device ==> cpu (ex: reset button)
