USB51S库一共有3个文件，包括USB51S.LIB，ISR.C，ISR.H（为了增加USB通信的灵活性，并没有把所有的子程序都封装倒USB51S.LIB，而是在ISR.C建立部分通信程序，这样方便用户修改-USB51S for a total of three documents, including USB51S.LIB, ISR.C, ISR.H (USB communication in order to increase the flexibility, and not all the subroutine package, reversing USB51S.LIB, but ISR.C establish some communication procedures, such convenience users changes