A control system includes a data access circuit and a control circuit. The system coordinates an asynchronous FIFO process between a write circuit operating according to a first clock and a read circuit operating according to a second clock. The data access circuit controls the write circuit to write data into a memory buffer and controls the read circuit to read the data from the memory buffer. The control circuit generates a write index according to the first clock and a read index according to the second clock. The control circuit calculates multiple water levels according to the write index and the read index and obtains a median water level. The control circuit controls the access circuit to execute the asynchronous FIFO process at a time point corresponding to the median water level, so that a data exchange is performed via the memory buffer.