Patent ID: 8762764
Filing Date: 2014-06-24
Classification: G01R

Abstract:
1. A method, comprising: receiving a first potentially unreliable clock signal having a first frequency; receiving a second reliable clock signal having a second frequency, wherein the first frequency and the second frequency should have an expected relationship; and determining whether the first potentially unreliable clock signal has changed with respect to the second reliable clock signal by determining an actual relationship between the first potentially unreliable clock signal and the second reliable clock signal and generating an alarm signal if the actual relationship is different from the expected relationship, wherein determining the actual relationship between the first potentially unreliable clock signal and the second reliable clock signal comprises clocking an edge through a continuous loop of a plurality of storage elements, wherein at least two of the plurality of storage elements in the continuous loop are clocked by the first potentially unreliable clock signal and at least two other storage elements of the plurality of storage elements in the continuous loop are clocked by the second reliable clock signal.