Microcontroller system and operating method for secure device locking using counter and timer

A method for operating a microcontroller system having a microcontroller, a device which is controllable by the microcontroller, and a monitoring device, comprising:

• executing, by the microcontroller, an operation preparation program at each start and under a predefined exceptional condition during operation;
• changing, by the microcontroller, to a normal operation program after the operation preparation program has been executed;
• outputting, by the microcontroller and under a control of the normal operation program, a normal operation indicating signal;
• monitoring, by the monitoring device, whether the microcontroller is executing the normal operation program by reference to the normal operation indicating signal;
• transferring, by the monitoring device, the controllable device into a secured state if the normal operation indicating signal is absent;
• locking the controllable device, by the monitoring device, in the secured state if the normal operation indicating signal is absent over a predefined period of time;
• incrementing a register of the monitoring device each time the predefined exceptional condition occurs;
• locking the controllable device, by the monitoring device, in the secured state if a content of the resister reaches a predefined value;
• and
• selecting, by the monitoring device, the predefined time period after which the secured state is locked when the normal operation indicating signal is absent such that it is longer when the exceptional conditions are present than when the exceptional conditions are absent.