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K25 LLS wakeup results in COP reset

Question asked by matthews on Jan 1, 2016
Latest reply on Jan 2, 2016 by Mark Butcher

I am running software on a K25. I successfully can enter and exit LLS low power mode when the watchdog COP is not enabled. I am using the LPTMR to wakeup the processor every 120 seconds. (Code resembles the example found here: Starting Point for Kinetis Low Power LLS Mode | MCU on Eclipse )


When I wakeup from LLS with no watchdog enabled code execution resumes on the instruction following the WFI. With the watchdog enabled, code execution also resumes after the WFI. I immediately service the watchdog but the processor resets with a COP reset shortly after waking up. Any ideas why the watchdog is tripping even though I am servicing it?


The watchdog is using the LPO 1 kHz clock. The reference manual indicates when the 1 kHz clock source is selected, the COP counter is re-initialized to zero upon entry to either debug mode or stop (including VLPS or LLS) mode. The counter begins from zero upon exit from debug mode or stop mode. Something isn't adding up.


My watchdog timeout is set to 1.024 seconds.