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Our Board witch MC9S12XET256 when there was electromagnetic signals, would be stay in current dead sometimes, not reset

Question asked by hongjian zhang on Dec 27, 2016
Latest reply on Dec 28, 2016 by lama

A few days before, I push a question about our board with hy64 was influenced by cellphone call, and that mcu could go to reset every time, but today another board with mc9s12xet256 couldn't go to reset sometimes, it reset sometimes and then dead, only reconnect the power can save it.  


We use outside oscillator, and init it at the beginning of main program, and then config the pll module. at last we open the cop watchdog.


I think this state is that: our watchdog was used the first time of the electromagnetic signals disturb and reset, but when the mcu begin to work after reset, before our cop watchdog begin useful there was electromagnetic signals disturb still,and the program go into a illegal address or go into somewhere and couldn't go into normal state. 


I don't understand why the chip designer not open the cop watchdog at the beginning of the reset,  if it was what I said above, how can we avoid such thing? Besides, my opinion of the problem, I can't make sure ,only my thoughts.