设计一个频率测量仪,要求可测被测信号的频率并将转速值在四个LED上现实出来，用8253采样点电动机产生的转速脉冲测频率。 为微机接口课程设计，成绩中等。-Design a frequency meter, required frequency of the signal can be measured and the value of speed out of the four LED on the reality, with 8253 sample points generated by