只用单片机实现20Mhz不现实,但可以把频率信号分频,比附超过100K之后就给他2分频,随着频率增加,分频值增加,分频电路需另加硬件,然后分档,分档后的频率测量程序可以用下面的方法测量.-

20Mhz MCU only unrealistic, but the frequency of the signal frequency, after the analogy gave him more than 100K divided by 2, as the frequency increases, the value of increased frequency, frequency divider circuit are subject to hardware, and then sub-file, sub-file after the frequency measurement process can be measured using the following method.