介绍了双计数器多周期同步法频率测量原理，给出了用单片机实现的具体实现方案。
The paper introduces the principle of frequency measure based on double-counter and multi-periods pulse synchronization method, and the designing with microprocessor is offered.
用LED数码管显示计数器t0的计数值，包含51单片机寄存器定义的头文件。
Use LED digital display counter plan of tube T0 numerical, including 51 SCM registers definition of header files.
说明：51单片机外中断实验C源码，两个实验：1、外中断计数2位数码管显示；2、外中断计数器。
SCM experiment C source code external interruption, two experiments: 1, outside interrupt count two digital tube display 2 and external interruption counter.
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