怎么知道双缓冲区的大小呢？ 根据DI_AsyncClear的函数说明：I16 DI_AsyncClear (U16 CardNumber, U32 *AccessCnt) AccessCnt : The number of digital input data that has been transferred at the time the call to DI_AsyncClear(). If double-buffered mode is enabled, AccessCnt returns the next position after the position the last data is stored in the circular buffer. If the AccessCnt execeeds the half size of circular buffer, call ... 就是说，如果AccessCnt超过了缓冲的一半，就需要再次调用相应函数读取剩下的数据 可是，究竟缓冲区大小的一半，是多少？对PCI-7200而言。