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FXTH871 PWU Flag Bits Unresponsive

Question asked by Carl Saunders on Jul 3, 2018

Hello Community,


I am running in to a problem with the FXTH871, in particular with the PWU Flag Bits.


There are 2 flag bits that I can see that on the datasheet say will be set whenever a Periodic Wake Up is what removes the MCU from SLEEP modes.  These 2 bits are: PWUCS0_WUF & SIMSES_PWUF.


*From the datasheet:


PWUCS0_WUF: Wakeup Interrupt Flag — The WUF bit indicates when a wakeup interrupt has been generated by the PWU. This bit is cleared by writing a one to the WUFAK bit. Writing a zero to this bit has no effect. Reset clears this bit.


SIMSES_PWUF: PWU Flag — This bit indicates that the PWU module caused the last exit from STOP mode.



Neither of these bits seems to be set when I use PWU to wake up the MCU from SLEEP modes.  I am certain that the PWU is responsible for the wake up as well because I can adjust the time on the PWU, and it correctly wakes up at whatever time I set it to.


I have attached the very simple code that I am running right now to this post.  I am hoping that somebody can answer to me