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