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Why was NVIC interrupt pending register not cleared by the reset switch on FRDM-K20D50M board?

Question asked by Yasuhiko Koumoto on Sep 26, 2014
Latest reply on Oct 2, 2014 by Yasuhiko Koumoto

Hello all,


I found strange phenomenon. That is, NVIC interrupt pending registers (i.e NVIC_ISPR0 and NVIC_ICPR0) are not cleared by the reset switch on FRDM-K20D50M board.
The background is that I made a program which showed the wake up from the low power mode by RTC alarm interrupt but MCU exited from the low power mode suddenly after entering the mode for every second time. In the odd times, it succeeded. In the even times, it failed. I analyzed it and found NVIC interruts were pending even after reset. When I added NVIC interrupt clear code in the RTC setting routine, such slip phenomenon became not happened.
Can anyone answer that it is the correct behavior or the board problem?


Best regards,

Yasuhiko Koumoto.