To detect the period abnormality of the operation clock of an arithmetic part.
A first arithmetic part calculates a first difference as a difference between the period of a first clear signal and the period of a second clear signal, and when the first difference deviates from a predetermined range, determines that either the period of the operation clock of the first arithmetic part and the period of the operation clock of a second arithmetic part is abnormal. The second arithmetic part calculates a second difference as a difference between the period of the second clear signal and the period of the first clear signal, and when the second difference deviates from a predetermined range, determines that at least either the period of the operation clock of the second arithmetic part or the period of the operation clock of the first arithmetic part is abnormal.
HOSHINO TAKAMICHI
TAKAYAMA NAOKI
IKETOMI TSUTOMU
YABUUCHI TATSUSHI
MINEO TOMOAKI
