PURPOSE: To improve the reliability of a memory, minimize a decrease in throughput for the reliability improvement, and speed up processing by keeping a microprocessor in reading operation for the memory if data read out of the memory become abnormal, and ending the reading operation for the memory once by a memory control circuit and performing the reading operation again.

CONSTITUTION: This method is provided with the memory control circuit 2 which checks the normalcy of the data read out of the memory 3 when a microprocessor 1 reads the data out of the memory 3. Then if the data are abnormal, the memory control circuit 2 holds the microprocessor 3 in the reading operation while the reading of the memory 3 is ended once and performed again. Further, the memory control circuit 2 does not send out a response for ending the reading operation by the microprocessor 1 to the microprocessor if the data are abnormal.