I have started to develop an electronic control unit using MPC5634M. I have provided the SW preliminary. i have run the SW. In some cases which the system is running, the supply voltages is disconnected suddenly, After re connection of the system to supply voltage, the circuit hasn't any action. For example i would like to connect to the micro by Rs232 but i can't. But after some times (some hours in some cases or some days even), the system comes back to normal situation. I appreciate if some expert people can help me in this regard.