To solve the problem that with a WDT(watch dog timer) doing nothing else but interrupting a system after the timeout of the WDT, a system is stopped in the case of falling into a serious state where restoration from a fault can not be performed just by interruption.
The fault is coped with by the procedure of linking the WDTs in a plurality of stages, the procedure of having the linked WDTs strongly intervene the system stepwise, the interruption for a slight fault restorable by the interruption, unmaskable interruption for the fault of a middle degree which can not restored except by the unmaskable interruption and system reset for a serious fault which can not be restored except by reactivation. Also, by a WDT reset port provided with a plurality of ports for which validity and invalidity are determined by setting, the fault of a computer for which a plurality of processors are parallelly operated is monitored as well.
ARAI TOSHIAKI
SATO MASAHIDE
UKAI HIROKI
