System for detecting a runaway of a microcomputer

A system for detecting a runaway of a microcomputer, comprising:

• a memory storing a predetermined program having at least two predetermined check routines for detecting a runaway condition of said predetermined program;
• a microcomputer which carries out said predetermined program and supplies at least two passing signals by carrying out said at least two predetermined check routines, a first one of said passing signals being a set signal and a second succeeding one of said passing signals being a clear request signal;
• a control unit responsive to said at least two predetermined check routines and including a register set by said first one of said passing signals and logic means responsive to a state of said register and said second succeeding one of said passing signals for generating a detecting signal if said register is not set when said clear request signal is generated by said microcomputer and a clear signal if said register is set when said clear request signal is generated;
• and
• a timer reset by said clear signal, said timer generating an overflow signal to said microcomputer if not reset before a predetermined count is reached, either of said detecting signal or said overflow signal indicating a runaway condition.