LPC4357: Cannot detect watchdog reset

[johanborkhuis]

I am trying to implement the WWDT function in the LPC4357. According to the user manual (section 38.5) I should be able to read the Watchog Mode register and determine if a watchdog reset was performed:

When the Watchdog Timer is configured so that a watchdog event will cause a reset and the counter reaches zero, the CPU will be reset, loading the stack pointer and program counter from the vector table as in the case of external reset. The Watchdog time-out flag (WDTOF) can be examined to determine if the Watchdog has caused the reset condition. The WDTOF flag must be cleared by software.

After a reset however the WDTOF is always 0, even if I break inside the Reset handler. How can I determine if the reset was caused by a watchdog timeout?

Regards,

Johan Borkhuis

[kerryzhou · Accepted solution]

Hi Johan,

    Thanks a lot for your patience.

    I already get the feedback from our according department. This problem already be confirmed, WDTOF can't be used as the watchdog timeout reset flag.

    Now, a workaround may help you.

    Just refer to use RGU mechanism with software flag to do it.

   You can define a variable in the RAM, after you enable watchdog, you can give a fixed value to that variable, then check the variable value before RAM initialization after code start, if it is the data which you defined after enable the watchdog, it means the reset is caused by the watchdog reset.

   Wish it helps you. Until now, I didn't find any other useful register to detect the watchdog timeout reset in LPC4357, so you can try the above RAM method workaround.

Have a great day,
Kerry

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[johanborkhuis]

Kerry,

Thank you for the answer. We had already made a solution that was comparable to this one, not using the RAM but using the RTC scratch area, as this area will not be cleaned by any startup code and can also be used to store other restart reasons.

Regards,

Johan Borkhuis

[kerryzhou]

Hi Johan Borkhuis,

   Thank you for your question.

   After the test on my side, I also reproduced your problem, I already help you to check it with our according department.

  Any updated information, will let you know, please wait patiently.

Kerry

[johanborkhuis]

Kerry,

Did you already get an answer from the other department?

Regard,

Johan Borkhuis

[kerryzhou]

Hi Johan,

   Our according department also reproduced this problem, they are still checking it now.

  Any updated information, I will let you know.

  Thanks a lot for your understanding.

Kerry