1硬件初始化，与CPU相关的配置，SSIO功能设置2SD卡的数据包、命令索引表和命令回应3命令相应的实现，读写SD卡，命令协议的封包拆包4SD卡配置的相关结构体信息分析（CID、CSD）-a hardware initialization, and the CPU configuration, SSIO 2SD cards feature set of data packets, orders table and orders to respond to three orders corresponding to achieve, SD card reader, orders agreement packet unpacking Four card configuration of the structure of information analysis (CID, CSD)