registers which determine if the digital pin is output mode or input mode.
registers for bi-directional I/O.
registers to control digital I/O.
register that controls the reference voltage, the presentation of the ADC conversion and analog channel selection.
register to control AD conversion.
registers which store the result of AD conversion.
registers to control timers and counters.
registers to set the duty ratio for PWM output.
registers related to timer interruption.
Definitions of the interrupt vectors.
registers incremented by each timer clock.
registers to control timer interruption.
registers to control external interrupts.
registers related to Universal Synchronous and Asynchronous serial Receiver and Transmitter.