I am using MKM34Z256VLL7 controller in my application. During development I stuck up in one critical issue i.e., Micro controller damage and also it is not able to reprogram.
While scrutinizing the issue, I found that if I connect - disconnect the Micro UART connection (Pin 91 and Pin 92) to external communication devices then micros are getting damaged; UART is running on 3.3V supply/signal level.
Another in recent experience, Micro damaged just while connecting the DSO - oscilloscope probe ground to micro ground. I checked the oscilloscope, its ground was isolated to mains supply and board remains untouched so there is no electrical over stress. Here Micro controller supply remains 3.3V but reset signal is permanently remains at low 0V level. Also I am not able to reprogram it.
Can you please help me to get rid out of this critical issues.