The RTC can generate events at periodic intervals, allowing for direct peripheral actions without CPU intervention. The periodic events can be generated on the upper eight bits of the RTC prescaler, and will be generated on the rising edge transition of the specified bit. The resulting periodic frequency can be calculated by the following formula:
Where refers to the asynchronous clock is set up in the RTC module configuration. The n parameter is the event source generator index of the RTC module. If the asynchronous clock is operated at the recommended frequency of 1KHz, the formula results in the values shown in Table 14-1.
Table 14-1. RTC Event Frequencies for Each Prescaler Bit Using a 1KHz Clock
n
Periodic event
7
1Hz
6
2Hz
5
4Hz
4
8Hz
3
16Hz
2
32Hz
1
64Hz
0
128Hz
Note: The connection of events between modules requires the use of the SAM Event System (EVENTS) Driver to route output event of one module to the the input event of another. For more information on event routing, refer to the event driver documentation.
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