Low-Power Oscillator

The ATWINC15x0B has an internal 32 kHz clock to provide timing information to various Sleep functions. Alternatively, the ATWINC15x0B allows an 32 kHz external clock for this purpose, which is provided through pin 24 (RTC_CLK). The software is used to select between the internal clock and the external clock.
Note: The current software implementation does not require an 32.768 kHz clock.

The internal low-power clock is a ring-oscillator and has accuracy within 10,000 ppm. When using the internal low-power clock, the advance wake-up time in the beacon monitoring mode must be increased to 1% of the sleep time to compensate for the oscillator inaccuracy. For example, for the DTIM interval value of 1, wake-up time must be increased by 1 ms.