Low power mode and watchdog operation

[scottyevans]

Hello,

I'm workng with a KL02 device and have it going to sleep every 30 seconds when a particular input is not high. I'm finding that this works when the watchdog is disabled but not when it is enabled.

does the watchdog fire if the device goes into sleep? I'm guessing that if the watchdog counter isnt reset (as I'm doing continuously in the program) the watchdog will reset.

[jingpan]

hi Scott,

The COP watchdog will not generate a interrupt to wakeup the MCU. Since in sleep mode  COP continue to work, I guess the MCU maybe reseted by watchdog.  You'd better feed dog periodically before watchdog reset.

Regards

[scottyevans]

Hi Jing

I am servicing the watchdog alot during operation and am doing it just before it goes to sleep (writing 0x55 and 0xAA in the SRVCOP register).

Are you saying that the COP continues to count while in sleep mode? this would explain things. how would I stop it while in sleep mode? obviously i dont want the processor to reset if it goes to sleep

Regards

[mjbcswitzerland]

Hi

When you write SLEEP mode which low leakage mode is involved (WAIT, STOP, VLPS, VLLSx)?

Regards

Mark

[scottyevans]

Hi Mark

Im going into VLPS. The datasheet suggests that it should be static in this mode. So i was expecting it to cease, and then continue from where it was.

Im using the internal clock, so Id expect it to reset upon entry, but not to count as its in VLPS

Regards

[mjbcswitzerland]

Scott

I have used VLPS on many KL parts with enabled COP and never experienced a reset (using LPO set to 1.024s). Therefore I don't expect the behavior that you are seeing....

Regards

Mark