Electronic apparatus with memory backup system

DETAILED DESCRIPTION Accordingly, an object of the invention is to provide an electronic apparatus capable of exactly deciding, during interruption of power supply thereto, validity of data retained in a memory with the aid of a memory backup power source.
Another object resides in providing an electronic apparatus adapted to ascertain the validity of the memory by checking the voltage of a memory backup power source prior to charging the memory backup power source, when power supply to the apparatus is resumed.
A further object is to provide an electronic apparatus wherein data writing and data reading are prohibited with regard to the memory, in case the voltage of a backup memory power source is below a predetermined value at the time power is again supplied.
A preferred embodiment of the present invention comprises a memory for storing data therein, a memory backup power source for furnishing electric power to the memory when power supply to the electronic apparatus is interrupted, a circuit for charging the memory backup power source after resumption of the power supply to the apparatus, voltage checking circuit for generating an error signal when the voltage of the memory backup power source is below a predetermined value, and control circuit for temporarily preventing the action of the charging circuit to the memory backup power source upon resumption of the power to the apparatus, and thereby render the action of the voltage checking circuit effectual.