sd卡指令数据包的封装与命令协议相关文件说明，改文件多SD卡的通信命令和数据格式 做了详细的解释和总结，文章的各方面介绍都很形象具体，对开发SD卡的朋友一定是个不可或缺的资料。-sd card packaging and instruction command packet protocol related documentation, change the file number SD card communication command and data format of a detail