29.4.5.1 Start Event

The start event for the counter/timer start is selected using the START bits in the TUxyHLT register. The available options include:
  1. No hardware Start: The counter/timer starts when the ON bit is set. This is the software-based start option. Any Stop events are ignored, but will still cause a capture.
  2. Either edge of the ERS signal (edge-triggered): The counter/timer starts at the event of either the rising or falling edge of the ERS signal.
  3. Rising edge of the ERS signal (edge-triggered): The counter/timer starts at the event of a rising edge of the ERS signal. When the EPOL bit is set, the polarity is inverted and the counter/timer starts at the event of a falling edge of ERS signal. See Figure 29-10 for an example of rising ERS edge Start and either ERS edge Stop condition.
  4. ERS = 1 (level-triggered): The counter/timer starts at the presence of a logic one of the ERS signal. When the EPOL bit is set, the polarity is inverted and the counter/timer starts at the presence of a logic zero of the ERS signal. Any Stop events that occur when ERS = 1 (or 0, based on EPOL) are ignored, but will still cause a capture. See Figure 29-11 for an example of level-triggered Start.
Important:
  1. In the event of a level-triggered Start/Reset, the active level must be asserted for at least one timer clock period to ensure proper sampling. If the duration of the asserted level is less than one timer clock, there is a possibility of the level trigger being missed and not sampled by the timer module.