PURPOSE: To guarantee the stored contents of a RAM and to prevent the generation of a fatal failure in an information processor by comparing the contents of the RAM backed up by a battery.

CONSTITUTION: Prior to the disconnection of a power supply for a device, an arithmetic processing circuit 3 specifies a prescribed address of the RAM 1 through an address bus 4. The data of a specific format are stored in the address through a data bus 5. When power is supplied to the device disconnected from a power source, the circuit 3 applies the address of the RAM 1 through the bus 4. The data stored in the address are read out from the RAM 1 and applied to a comparator 2 through a data bus 5. The data applied through the bus 5 are compared with the data of the specific format which are previously stored in the RAM 1 by the comparator 2. When a compared result applied from the comparator 2 through a signal line 6 indicates the discrepancy of both the data, the circuit 3 decides the destruction of the contents stored in the RAM 1.