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F29H85X-SOM-EVM: Inquiry on CPU Behavior After Entering NMI

Lawrence Wang
Prodigy 570 points
Part Number: F29H85X-SOM-EVM

Tool/software:

Hi experts,

Our customer has the following questions regarding CPU behavior after entering NMI:

  1. After the CPU enters NMI and performs the necessary flag-clearing operations, will the CPU automatically reset if no manual reset is triggered?
  2. Under what conditions will the CPU automatically reset after entering NMI?
  3. Does entering NMI itself cause the MCU CPU to reset?
  4. What scenarios could lead to a passive reset of the CPU after entering NMI?
  5. After entering NMI, will the CPU remain in the NMI state, or are there certain conditions under which it can return to normal operating mode?
  • 0
    TI__Genius 13135 points

    Hi,

    Lawrence Wang said:
    After the CPU enters NMI and performs the necessary flag-clearing operations, will the CPU automatically reset if no manual reset is triggered?

    After CPU enters NMI and the ESM raw status register flags are cleared the NMIWD counter stops and resets to preload value. After this CPU does not reset. If needed reset can be triggered manually.

    Also if the error flags are not cleared then the NMIWD counter expires and reset is triggered by High priority watchdog event (high priority watchdog interrupt) output.

    Lawrence Wang said:
    Under what conditions will the CPU automatically reset after entering NMI?

    See explaination above.

    Lawrence Wang said:
    Does entering NMI itself cause the MCU CPU to reset?

    See above, no just entering NMI does not cause CPU to reset. The NMI WD counter in ESM has to expire to cause reset.

    Lawrence Wang said:
    After entering NMI, will the CPU remain in the NMI state, or are there certain conditions under which it can return to normal operating mode?

    Exiting NMI ISR will exit CPU NMI state. NMI is just like any other RTINT interrupt

    NMI should only occur under MCU critical error conditions. If user decides to clear error conditions and esm error flags to exit NMI isr and continue normal operation they can do so.

    Thanks