本例实现的检测是否有三路信号输入，如果有可输出一个高电平，同时可计算第一路与第三路之间相差的脉冲数，使用vhdl语言与图形结合的方法。-Achieved in this case detect three-way signal input, if there is a high output, while the first road and calculate the difference between the third way of pulses, using vhdl languag