Secured electronic device and process for measuring time

摘要

The circuit has counters (8, 12) timed with respective periods (T1, T2) by an external and internal oscillator (6, 14), respectively. The counter (12) is re-initialized when the counter (8) contents are multiple of a preset value (N1). A comparator (18) activates an alarm signal when the counter (12) reaches a preset value (N2) such that product of value (N2) and period (T2) is higher than product of value (N1) and period (T1). An Independent claim is also included for a method of measuring time using a counter.