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 20-3. Event Generators in TCA
Generator NameDescriptionEvent TypeGenerating Clock DomainLength of Event
PeripheralEvent
TCAnOVF_LUNF

Normal mode: Overflow

Split mode: Low byte timer underflow

PulseCLK_PEROne CLK_PER period
HUNF

Normal mode: Not available

Split mode: High byte timer underflow

PulseCLK_PEROne CLK_PER period
CMP0

Normal mode: Compare Channel 0 match

Split mode: Low byte timer Compare Channel 0 match

PulseCLK_PEROne CLK_PER period
CMP1

Normal mode: Compare Channel 1 match

Split mode: Low byte timer Compare Channel 1 match

PulseCLK_PEROne CLK_PER period
CMP2

Normal mode: Compare Channel 2 match

Split mode: Low byte timer Compare Channel 2 match

PulseCLK_PEROne 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 20-4. Event User in TCA
User NameDescriptionInput DetectionAsync/Sync
PeripheralInput
TCAnCNTCount on a positive event edgeEdgeSync
Count on any event edgeEdgeSync
Count while the event signal is highLevelSync
The event level controls the count direction, up when low and down when highLevelSync
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.