I am working on Low power mode on Kinetis K21. Based on page 31 in AN4503, I got this:
If the MCG was in PEE when LLS mode was entered from Run mode, it will exit in PBE mode. Note that any module's clocks sourced from the PLL have been off in LLS. Upon wake-up, the frequency will be changed and therefore baud rates and timer counter time bases will change as well. The PLL is functioning but not engaged.
Does this mean I have to reset MCG again to switch it from PBE to PEE once it exits from LLS mode? Or I just need wait a little bit for PLL and system will be automatically back to PEE mode?