28.6.4 Events

The PORT allows input events to control individual I/O pins. These input events (EVU0-3) are generated by the EVSYS module and can originate from a different clock domain than the PORT module’s clock domain.

The PORT can perform the following actions:

• Output (OUT): I/O pin will be set when the incoming event has a high level ('1') and cleared when the incoming event has a low-level ('0').
• Set (SET): I/O pin will be set when an incoming event is detected.
• Clear (CLR): I/O pin will be cleared when an incoming event is detected.
• Toggle (TGL): I/O pin will toggle when an incoming event is detected.

The Output event is sent to the pin without any internal latency. For SET, CLEAR, and TOGGLE event actions, the action will be executed up to three clock cycles after a rising edge.

The event actions can be configured with the Event Action m bit group in the Event Input Control register( EVCTRL.EVACTn). Writing a '1' to a PORT Event Enable Input m of the Event Control register (EVCTRL.PORTEIn) enables the corresponding action on input event. Writing '0' to this bit disables the corresponding action on input event. Several actions can be enabled for incoming events. If several events are connected to the peripheral, any enabled action will be taken for any of the incoming events. Refer to the section “ EVSYS – Event System” for additional information on configuring the Event System.

Each event input can address one and only one I/O pin at a time. The selection of the pin is indicated by the PORT Event Pin Identifier of the Event Input Control register (EVCTR.PIDn). On the other hand, one I/O pin can be addressed by up to four different input events. To avoid action conflict on the output value of the register (OUT) of this particular I/O pin, only one action is performed according to the table below. This truth table can be applied to any SET/CLR/TGL configuration from two to four active input events.

Be careful when the event is Output (OUT) to pin. Because the events are received asynchronously, the I/O pin may have unpredictable levels, depending on the timing of when the events are received. When several events are output to the same pin, the lowest event line will get the access. All other events will be ignored.