17.3.2.1 Basic Functions

Each I/O pin Pxn can be controlled by the registers in PORTx. 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 PORTx.DIR register to '1'. This can be done by writing bit n in the PORTx.DIRSET register to '1', which will avoid disturbing the configuration of other pins in that group. The n^th bit in the PORTx.OUT register must be written to the desired output value.

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

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

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