Datasheet

23.6.2 Basic Operation

23.6.2.1 Initialization

After reset, all standard function device I/O pads are connected to the PORT with outputs tri-stated and

input buffers disabled, even if there is no clock running.

However, specific pins, such as those used for connection to a debugger, may be configured differently,

as required by their special function.

23.6.2.2 Operation

Each I/O pin Pxy can be controlled by the registers in PORT. Each PORT group x has its own set of

PORT registers, with a base address at byte address (PORT + 0x80 * group index) (A corresponds to

group index 0, B to 1, etc...). Within that set of registers, the pin index is y, from 0 to 31.

Refer to I/O Multiplexing and Considerations for details on available pin configuration and PORT groups.

Configuring Pins as Output

To use pin Pxy as an output, write bit y of the DIR register to '1'. This can also be done by writing bit y in

the DIRSET register to '1' - this will avoid disturbing the configuration of other pins in that group. The y bit

in the OUT register must be written to the desired output value.

Similarly, writing an OUTSET bit to '1' will set the corresponding bit in the OUT register to '1'. Writing a bit

in OUTCLR to '1' will set that bit in OUT to zero. Writing a bit in OUTTGL to '1' will toggle that bit in OUT.

Configuring Pins as Input

To use pin Pxy as an input, bit y in the DIR register must be written to '0'. This can also be done by writing

bit y in the DIRCLR register to '1' - this will avoid disturbing the configuration of other pins in that group.

The input value can be read from bit y in register IN as soon as the INEN bit in the Pin Configuration

By default, the input synchronizer is clocked only when an input read is requested. This will delay the

read operation by two cycles of the PORT clock. To remove the delay, the input synchronizers for each

PORT group of eight pins can be configured to be always active, but this will increase power

consumption. This is enabled by writing '1' to the corresponding SAMPLINGn bit field of the CTRL

Using Alternative Peripheral Functions

To use pin Pxy as one of the available peripheral functions, the corresponding PMUXEN bit of the

PINCFGy register must be '1'. The PINCFGy register for pin Pxy is at byte offset (PINCFG0 + y).

The peripheral function can be selected by setting the PMUXO or PMUXE in the PMUXn register. The

PMUXO/PMUXE is at byte offset PMUX0 + (y/2). The chosen peripheral must also be configured and

enabled.