SELF-DIAGNOSTIC SYSTEM FOR A/D CONVERSION SECTION OF MICROCOMPUTER

PURPOSE:To attain clear fail processing discrimination of an A/D converter section by inputting a power voltage and a reference voltage fed to the A/D converter section from separate circuits. CONSTITUTION:An A/D-converted value being a half the inputted power supply voltage is compared with an upper limit value (RMAX) and a lower limit (RMIN) respectively and when the limit is exceeded, an error processing of the A/D converter section is implemented and when the limit is not exceeded, a normal processing of the A/D converter section is implemented. Since the power voltage and the reference voltage are inputted from separate circuits, i.e., a power supply circuit 15 and a reference voltage generating circuit 16, a standard power supply circuit is adopted for the power supply circuit 15 and a highly accurate circuit is employed for only the reference voltage generating circuit 16. Then a highly accurate and inexpensive IC or the like is used for the reference voltage generating circuit 16 to easily realize the discrimination of the absolute voltage of the said analog sensor 12.