Microcomputer runaway detection and start-up device

摘要

PURPOSE:To obtain an inexpensive and compact device by sharing an oscillation circuit for detecting the runaway and starting. CONSTITUTION:At normal working of a microcomputer, the oscillation of an oscillation circuit 2 is stopped by an oscillation stop circuit. At runaway of the microcomputer, the microcomputer is reset by the oscillation of the circuit 2. When the operation of the microcomputer is stopped, a non-reset signal is inputted to the microcomputer via a signal switch circuit. At the same time, the output signal of the circuit 2 is inputted to a start terminal for the starting purpose. That is, a microcomputer 1 has a runaway and no pulse is outputted from an output port P01. In such a case, a transistor 9 is cut off and the circuit 2 works. Then an output pulse is applied to a reset terminal Ta through an OR gate 17. In such a constitution, the number of oscillation circuits can be decreased so as to attain a compact structure.