主要实现在通过FPGA NIOS中，对SD进行初使化，读，写文件内容，但其是以块的形式写进SD里的，而不是以.TXT形式写入的。-Mainly achieved through the FPGA NIOS, the pairs of SD to perform initialization, reading and writing file content, but it is in the form of blocks written into the SD inside, rather th