For an unknown reason our MCU (MCF52110CAE80) freezes and the only way to restart it is a power cycle.
When the MCU freezes, pulling RSTI pin low does not reset the MCU. We have a Voltage Supervisor with Watchdog Timer connected on RSTI pin but it can not do its job when the MCU is in this state.
When the MCU is in this state, RSTO pin is always low. It seems the MCU is stuck in reset and can not start. Also, the PSTCLK/CLKOUT pin is steady (high or low) on the scope instead of oscillating at 80MHz, so it may be the on-chip oscillator or the PLL that are not working.
Sometimes, the same MCU freezes 5 times a day and, then, it does not freeze for a week. We do not know the cause of the problem, but since it is much more common in the winter when the heating system is working, so it might be ESD.
Does someone know a way to prevent this "stuck in reset" state?
Note: The MCU page of our schematics is attached