SD卡在现在的日常生活与工作中使用非常广泛，时下已经成为最为通用的数据存储卡。在诸如MP3、数码相机等设备上也都采用SD卡作为其存储设备。SD卡之所以得到如此广泛的使用，是因为它价格低廉、存储容量大、使用方便、通用性与安全性强等优点。既然它有着这么多优点，那么如果将它加入到单片机应用开发系统中来，将使系统变得更加出色。这就要求对SD卡的硬件与读写时序进行研究。对于SD卡的硬件结构，在官方的文档上有很详细的介绍，如SD卡内的存储器结构、存储单元组织方式等内容。要实现对它的读写，最核心的是它的时序，笔者在经过了实际的测试后，使用51单片机成功实现了对SD卡的扇区读写，并对其读写速度进行了评估。-There are two optional SD card communication protocols: SD mode and SPI mode. SD model is a standard SD card reading and writing, but in the selection of SD mode, often need to select the SD card controller interface with MCU, or SD card to join the additional control unit to support the SD card reader. However, AT89C52 microcontroller is not integrated SD card controller interface to SD mode if the selected communication would in effect increase the cost of hardware products. The time to read and write data in SD card is not very demanding circumstances, the use SPI mode can say is the best solution. SPI, mode because, by four lines on all the data can be exchanged, and Du Mu Qian Ji Cheng MCU market, there are many existing SPI interface circuit using SPI mode on the SD card reader can be greatly Jianhua Cao Zuo hardware design.