Rationality check

The PCM measures and analyses the received 'free running timer' during a calibrated monitoring period with help of an internal clocked reference timer. So the deviation of synchronism per defined monitoring period is analyzed. The diagnosis is retriggered after expiration of the monitoring time period and starts with resynchronizing of the internal clocked reference timer with the externally clocked free running timer.

If, during the monitoring period, the absolute time difference between the internal reference timer and the external free running timer exceeds a calibrated threshold for a calibrated period of time, a plausibility fault CUHR is set.