The current two reset reasons are mia_isResetReasonPor and mia_isResetReasonTimedWake. You may try to ascertain whether a reset is due to watchdog by observing for it when the watchdog is enabled and disabled.
Our device is using with BLE 20737S and when system is reset due to some exception, I try to
query mia_isResetReasonPor() but the reason code = 1 which is the same as normal power-on reason.
Is that correct or wrong; I originally think there will have different reason from normal power-on reason.
The reason is correct. But it did not say what is the trigger to your exception.