说明：  用单片机设计的测速表源程序，测量转速，使用霍尔传感器，被测轴安装有12只磁钢，即转轴每转一周，产生12个脉冲，要求将转速值（转/分）显示在数码管上。
(Speed table with a single chip design source, measurement speed, use the Hall sensor, measured shaft equipped with 12 magnets, which turns a shaft to produce 12 pulses, requested speed value (r/min) appears in the Digital tube.)