Apparatus and method for detecting clock tampering

Disclosed is a method for detecting clock tampering. In the method a plurality of resettable delay line segments are provided. Resettable delay line segments between a resettable delay line segment associated with a minimum delay time and a resettable delay line segment associated with a maximum delay time are each associated with discretely increasing delay times. A monotone signal is provided during a clock evaluate time period associated with a clock. The monotone signal is delayed using each of the plurality of resettable delay line segments to generate a respective plurality of delayed monotone signals. The clock is used to trigger an evaluate circuit that uses the plurality of delayed monotone signals to detect a clock fault.