DIGITAL ARITHMETIC UNIT

PURPOSE:To ensure a normal writing operation despite the absence of a power holding capacitor by preparing an EEPROM and writing the decided data out of the arithmetic result together with the flag data. CONSTITUTION:Plural process signals undergo the A/D conversion and a microprocessor of a digital arithmetic part 2 applies the arithmetic operations to these digital signals. These arithmetic results are stored in a memory RAM 3. A read/write control part 4 writes the decided data into the blocks B1 and B2 of an EEPROM 1 and controls them out of those arithmetic results. In this case, the flag data is also written to show whether the data is normally written or not. Thus the data written into the blocks B1 or B2 is correctly held despite the occurrence of an unexpected trouble. As a result, the data can be correctly written into the EEPROM 1 even with no use of a power holding capacitor.