Patent ID: 8311169
Filing Date: 2012-11-13
Classification: G01R,H03K,H04L

Abstract:
1. An automatic frequency monitoring circuit that automatically monitors a frequency of a clock related to an operation of a device to be monitored comprising: a frequency detector that detects, upon detecting a predetermined momentum, frequencies of a target clock during a predetermined time for a plurality number of times and treats as a detection frequency of the target clock, an average of the frequencies that are detected for the plurality number of times; and a frequency monitor that monitors, upon the frequency detector detecting the detection frequency of the target clock, whether the frequency of the target clock during the predetermined time is within a predetermined fluctuation range based on the detection frequency, wherein the frequency monitor determines whether the frequency monitor monitors whether the frequency of the target clock during the predetermined time is within the predetermined fluctuation range, based on whether a difference or a ratio between a first detection frequency of the target clock that is previously detected by the frequency detector and a second detection frequency of the target clock that is currently detected by the frequency detector exceeds a predetermined threshold, wherein the frequency monitor detects, upon detecting the predetermined momentum only upon the difference or the ratio between the first detection frequency of the target clock that is previously detected by the frequency detector and the second detection frequency of the target clock that is currently detected by the frequency detector exceeding the predetermined threshold during monitoring the target clock, that the target clock is updated, and monitors whether the frequency of the target clock during the predetermined time is within the predetermined fluctuation range based on the second detection frequency.