ABNORMAL STATE DETECTION CIRCUIT FOR MICROCOMPUTER

摘要

PROBLEM TO BE SOLVED: To detect abnormality such as the runaway of the software of a microcomputer or the oscillation stoppage of an oscillation circuit or the like by outputting an identification signal different from a prescribed identification signal in the case that one of the output signals of first and second reception circuits is not prescribed logic. SOLUTION: Pulse signals originated from the output port P1 of the microcomputer are directly inputted to the first reception circuit (circuit A11) and inverted in an inverter 3 and inputted to the second reception circuit (circuit B11). Then, when the microcomputer 111 performs a normal operation, the output signals B1 and C1 of the circuits A11 and B11 both become a high level and the high level signals are inputted to a NAND circuit 9. At the time, the output of the NAND circuit 9 becomes a low level. Inversely, when the microcomputer 111 performs an abnormal operation, the output signal B1 of the circuit A11 for instance becomes the high level and the output signal C1 of the circuit B11 becomes the low level. Both signals B1 and C1 are inputted to the NAND circuit 9. At the time, the output of the NAND circuit 9 becomes the high level and the identification signal is different.