流传的用SPI驱动SD卡的程序基本都是针对没有FIFO的SPI接口的，这样做程序比较通用；但是如果处理器的SPI接口有FIFO的话，那么FIFO的性能就浪费了。其实把程序稍加改动，就可以大幅度提高SD卡的读取速度-Compared to general procedure is in sending a continuous and successive spread with the SPI driver SD card program is the basic for no FIFO SPI interface, this procedure is relatively general　but if processor SPI interface with FIFO, then performance of FIFO is wasted. In fact, the program a little change, you can greatly improve the SD card reading speed