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What are the differences in the effect of Watchdog reset, POR, external reset signal, and SYSRESETREQ?

Question asked by Atilla Filiz on Jul 4, 2019
Latest reply on Jul 8, 2019 by Jing Pan

I understand they are different reset sources, but is there any difference in what modules/peripherals they reset or not?


We do have an MK64FX board that uses i2s and DMA. Under some conditions (when the DMA IRQ handler is not fast enough to return before the next IRQ arrives) we get into a state where the watchdog timer might reset the system.

Here is what I have tried:


1. When the overflow is detected, run the function that initializes the i2s bus and DMA again. The audio data I read from now on is invalid, even after resetting the external audio chip as well.

2. When the overflow is detected, let the watchdog timer reset the chip. Similar to 1, the audio input is bogus.

3. Similar to 2, but during bootup if there is a watchdog reset, we also issue a soft reset request using SYSRESETREQ bit. The audio is still similar 1 and 2.

4. After 1, 2, or 3 happens, I generate an external reset signal by pressing a button. The whole hardware is re-initialized correctly.  Everything works again.

5. After a power-on, audio works without issues.


My question is, what might be happening that an external reset pulse can fix, but a watchdog or soft reset cannot?