Sleep Mode Operation; 21.10 Synchronization - Microchip Technology megaAVR 0 Series Manual

21.9

Sleep Mode Operation

The RTC will continue to operate in Idle Sleep mode. It will run in Standby Sleep mode if the RUNSTDBY
bit in RTC.CTRLA is set.
The PIT will continue to operate in any sleep mode.

21.10 Synchronization

Both the RTC and the PIT are asynchronous, operating from a different clock source (CLK_RTC)
independently of the main clock (CLK_PER). For Control and Count register updates, it will take a
number of RTC clock and/or peripheral clock cycles before an updated register value is available in a
register or until a configuration change has an effect on the RTC or PIT, respectively. This synchronization
time is described for each register in the Register Description section.
For some RTC registers, a Synchronization Busy flag is available (CMPBUSY, PERBUSY, CNTBUSY,
CTRLABUSY) in the STATUS register (RTC.STATUS).
For the RTC.PITCTRLA register, a Synchronization Busy flag (SYNCBUSY) is available in the PIT
STATUS register (RTC.PITSTATUS).
Check for busy should be performed before writing to the mentioned registers.
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2018 Microchip Technology Inc.
Datasheet Preliminary
®
megaAVR 0-Series
Real-Time Counter (RTC)
DS40002015A-page 261