在MSC-51的定时中T0和T1最常用，但像89s52中的T2却不怎么会用，本例子用T2实现精确1秒定时。,MSC-51 in the timing of the most commonly used T0 and T1, but T2 of 89s52 like how not to use, the example of T2 accurate with one seconds from time to time.

89s52单片机设计的具有小信号频率检测（小幅度模拟信号频率测量）功能和自动换挡测量功能的最低测量频率1Hz最高测量频率达到10MHz的频率计的ceil环境汇编语言编写的单片机程序（附频率计的protel设计原理图）-89s52 microcontroller designed with the small-signal frequency detection (small amplitude analog signal frequency measurement) functions and