16.3.2.1 Basic Functions

Each I/O pin Pxn can be controlled by the registers in PORT x. Each pin group x has its own set of PORT registers, the base address of the register set for pin n is at the byte address $\mathrm{plus}(\mathrm{PORT}, \mathrm{plus}(\mathrm{0x10}, n))$ . The index within that register set is n.

To use pin number n as an output only, write bit n of the PORT.DIR register to '1'. This can also be done by writing bit n in the PORT.DIRSET register to '1' - this will avoid disturbing the configuration of other pins in that group. The n^th bit in the PORT.OUT register must be written to the desired output value.

Similarly, writing a PORT.OUTSET bit to '1' will set the corresponding bit in the PORT.OUT register to '1'. Writing a bit in PORT.OUTCLR to '1' will clear that bit in PORT.OUT to zero. Writing a bit in PORT.OUTTGL or PORT.IN to '1' will toggle that bit in PORT.OUT.

To use pin n as an input, bit n in the PORT.DIR register must be written to '0' to disable the output driver. This can also be done by writing bit n in the PORT.DIRCLR register to '1' - this will avoid disturbing the configuration of other pins in that group. The input value can be read from bit n in register PORT.IN as long as the ISC bit is not set to INPUT_DISABLE.

Writing a bit to '1' in PORT.DIRTGL will toggle that bit in PORT.DIR, and toggle the direction of the corresponding pin.