自己写的一个频率计程序，用的是VHDL语言，功能已经实现，结果用8位数码管显示，精度达到小数点后3位，值得初学者看一看，测频原理是测周法-To write a frequency meter program, using VHDL language function has been achieved, the results with 8 digital display, accuracy of three decimal places, it is worth a look for begi