《TMS320x280x, 2801x, 2804x System Control and Interrupts Reference Guide 》在描述外部中断时提到，“The masked interrupts also contain a 16-bit free running up counter that is reset to zero when a valid interrupt edge is detected. This counter can be used to accurately time stamp the interrupt.”原文的意思是不是可以用这个计数器来计算两次中断之间的时间间隔？但中断发生时，这个计数器又会被清零，该怎么用啊？
