Abnormal frequency detection method and circuit thereof

The invention relates to an abnormal frequency detection method. The method is used for detecting whether the output frequency signals of a chip are abnormal. The abnormal frequency detection method includes the following steps that: first delayed frequency signals and second delayed frequency signals are provided according to output frequency signals, wherein the phases of the output frequency signals, the first delayed frequency signals and the second delayed frequency signals are different each other; and the first delayed frequency signals re sampled with the second delayed frequency signals, so that whether an abnormality occurs on the output frequency signals can be judged. 种异常频率检测方法，用于检测芯片的输出频率信号是否有异常，其中异常频率检测方法包括：根据输出频率信号来提供第延迟频率信号与第二延迟频率信号，其中输出频率信号、第延迟频率信号与第二延迟频率信号的相位互不相同；以及利用第二延迟频率信号来对第延迟频率信号进行取样，以判断输出频率信号是否发生异常。