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LPC43xx RTC: How to avoid reiniting after each Deep Power Down wakeup

Question asked by Kha Vo on Dec 10, 2016
Latest reply on Dec 28, 2016 by Kha Vo

Hi all,

I have to sleep the LPC4337 MCU in a long time, so I use RTC wake up from Deep Power Pown mode, but there is an issue with RTC initializing:


As LPC43xx RTC Datasheet:

The RTC is configured as follows:
• See Table 874 for clocking and power control. The 1 kHz output of the 32 kHz oscillator must be enabled in the CREG0 register in the CREG block (see Table 97).


But this is clock is disabled after reset (wake-up):

This mean I have to enable these bits each bootup (wakeup) and reinitialize whole RTC?


So my questions is: Does RTC need to reinitialize fully after wakeup? If not, how to do that.


PS. I did try to omit the initializing sequence on wake up, but in that case RTC alarm doesn't work any more so it doesn't wake up after second sleep (RTC time increases normally). I may miss somethings.


Kha Vo