Periodic electrical signal frequency monitoring systems and methods

A method of monitoring the frequency of a periodic electrical signal, comprising:

• counting pulses of a first periodic electrical signal to be monitored to generate a first count;
• counting pulses of a second periodic electrical signal to generate a second count;
• resetting one of the first count and the second count, to thereby restart the one of the first count and the second count, responsive to the other of the first count and the second count crossing a reset threshold;
• and
• determining whether a frequency error has occurred in the first periodic electrical signal based on whether the one of the first count and the second count crosses an alarm threshold.

A method of monitoring frequencies of periodic electrical signals, comprising:

• counting pulses of a plurality of periodic electrical signals to generate a respective plurality of counts, the plurality of counts having respective associated thresholds;
• detecting a crossing, by each of the plurality of counts, of each threshold associated with the count;
• and
• determining whether a frequency error has occurred based on whether the counts cross their respective thresholds in other than a particular sequence with respect to each other.