20.3.4 Events

The TCA can generate the events described in the table below. All event generators except TCAn_HUNF are shared between Normal mode and Split mode operation.
Table 20-2. Event Generators in TCA
Generator Name Description Event Type Generating Clock Domain Length of Event
Peripheral Event
TCAn OVF_LUNF

Normal mode: Overflow

Split mode: Low byte timer underflow

 Pulse CLK_PER One CLK_PER period
HUNF

Normal mode: Not available

Split mode: High byte timer underflow

 Pulse CLK_PER One CLK_PER period
CMP0

Normal mode: Compare Channel 0 match

Split mode: Low byte timer Compare Channel 0 match

 Pulse CLK_PER One CLK_PER period
CMP1

Normal mode: Compare Channel 1 match

Split mode: Low byte timer Compare Channel 1 match

 Pulse CLK_PER One CLK_PER period
CMP2

Normal mode: Compare Channel 2 match

Split mode: Low byte timer Compare Channel 2 match

 Pulse CLK_PER One CLK_PER period
Note: The conditions for generating an event are identical to those that will raise the corresponding interrupt flag in the TCAn.INTFLAGS register for both Normal mode and Split mode.
The TCA has one event user for detecting and acting upon input events. The table below describes the event user and the associated functionality.
Table 20-3. Event User in TCA
User Name Description Input Detection Async/Sync
Peripheral Input
TCAn CNT Count on a positive event edge Edge Sync
Count on any event edge Edge Sync
Count while the event signal is high Level Sync
The event level controls the count direction, up when low and down when high Level Sync
Note:
  1. Event inputs are not used in Split mode.
  2. Event actions with level input detection only work reliably if the event frequency is less than the timer’s frequency.

The specific actions described in the table above are selected by writing to the Event Action (EVACT) bit field in the Event Control (TCAn.EVCTRL) register. Input events are enabled by writing a ‘1’ to the Enable Count on Event Input (CNTEI) bit in the Event Control (TCAn.EVCTRL) register.

Refer to the Event System (EVSYS) chapter for more details regarding event types and Event System configuration.