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 corresp