In this mode, software must explicitly perform write operations when safe to do so.
This condition needs to be ensured by specific time-sensitive code.
In this mode, write operations are safe to do immediately after a falling edge of the
32KHz clock. Software should do the following sequence in order to prepare for MMR
writes in this mode.
- Identify the MMR writes to be performed and prepare a buffer of the writes to be
performed, so that a tight loop can perform the MMR writes.
- Poll RTC_SYNCPEND until two subsequent reads see a 1 and a 0 for the value of
O32K_CLK_OBS, which indicates the falling edge.
- If required, write RTC_KICK0 and RTC_KICK1 with the unlock values.
- Poll RTC_GENRAL_CTL.
- Perform each MMR write in sequence. MMR writes should be done in order of
increasing address offset.
- If required, write RTC_KICK0 with zeros to lock the functional lockout.
Once these steps are completed, MMR values should be stored safely in the ON
domain.