PURPOSE: To perform the monitoring of abnormality without interrupting the operation of a processor, by comparing the inspection data with the normal data of a program memory while the program memory is not accessed by a processor which executes a processing.

CONSTITUTION: During the outputting of the status signal (a) of a processor 20, the inspection cell of the program memory 10 is read in an input device 110. Next, the norm cell of a memory 30 corresponding to a read inspection data is read, and compared with the inspection cell at a comparator 130. If coincidence is obtained in a compared result, an inspection cell pointer is advanced by a unit quantity by an address arithmetic unit 120, and the same procedure is repeated hereafter. If discrepancy exists in the compared result, an output signal (b) is outputted to an error processing circuit 140. The error processing circuit 140 starts up an alarm device 40 by an alarm signal (d), and meanwhile, applies interruption on the processor 20 by a signal (c).