reset pin keeps low voltage after ECU running into problems

[Faker]

Hi,   

    There was a ECU using s32k144 which has a problem that its reset pin stays low voltage during state of bus sleep that is one of state of net mamagement of Autosar.  When ECU enters into NM_PREPARE_BUS_SLEEP, it calls SystemSoftwareReset() api. And then at NM_BUS_SLEEP state it calls api to enters VLPS mode . See Figure 1 for the pseudocode.

  I don't know which action can result reset keeping low.  Is it soft reset or after into VLPS hanging in an undetermined state or another conditions can lead to reset pin low voltage ?

    I use s32k144 that (PREDIV_SYS_CLK= 48 MHz) / (BUS CLK = 48 MHz) ,a ratio of 1:1. With this clock setting,mcu can hang in an undetermined state. What does phenomena of this state? Can it result reset pin to low voltage? See figure 2.

[lukaszadrapa]

Hi @Faker 

"undetermined state" is not defined exactly, so asserted reset is also possible. Please make sure the workaround is implemented:

Once it is fixed, are there any issues?

Regards,

Lukas

[Faker]

Once it is fixed, are there any issues?

It is hard to recurrence. So the above two situations are also our guess.

[lukaszadrapa · Accepted solution]

Except known erratum ERR011063, I can see only two possible reasons for asserted reset (i.e. reset asserted forever):

- reset is asserted by some external circuits, so it's not related to the microcontroller

- it's caused by internal low voltage detectors due to supply conditions - when reading your description, this is not that case.

So, I recommend to implement ERR011063 workaround and then test it again. I can understand that it's not easy to replicate it but such behavior corresponds to ERR011063.

There are no other known issues, so this is a very likely reason.

Regards,

Lukas

[Faker]

    I wonder soft reset api may go wrong to result reset pin staying low, Because we don't have any experience about reset pin low when ECU goes into problem.  We have located the problem happened when ECU is going to sleep, so we guess it may be happened at sotfware reset api or clock setting radio.Which of the two is more likely or another cases lead to this problem which reset pin keep low state.

    Any suggestions are welcome.Thanke you.