Some embodiments of the invention relate to an embedded processing system. The system includes a memory unit to store a plurality of operating instructions and a processing unit coupled to the memory unit. The processing unit can execute logical operations corresponding to respective operating instructions. An input/output (I/O) interface receives a first time-varying waveform and provides an I/O signal that is based on the first time-varying waveform. A comparison unit coupled to the processing unit and adapted to selectively assert an error signal based on whether the I/O signal has a predetermined relationship with a reference signal, wherein the predetermined relationship holds true during normal operation but fails to hold true when an unexpected event occurs and causes an unexpected change at least one of the I/O signal and reference signal.