SD卡读写模块2

张衍波

SD Memory Card (Secure Digital Memory Card) is a Flash-Based memory card that is specifically
designed to meet the security, capacity, performance and environment requirements inherent in
newly emerging audio and video consumer electronic devices. The SD Memory Card will include a
copyright protection mechanism that complies with the security of the SDMI standard and will be
faster and capable for higher Memory capacity. The SD Memory Card security system uses mutual
authentication and a "new cipher algorithm" to protect from illegal usage of the card content. A none
secured access to the user‘s own content is also available. The physical form factor, pin assignment
and data transfer protocol are forward compatible with the MultiMediaCard with some additions.
The SD Memory Card communication is based on an advanced 9-pin interface (Clock, Command,
4xData and 3xPower lines) designed to operate in a low voltage range. The communication protocol
is defined as a part of this specification. The SD Memory Card host interface supports regular
MultiMediaCard operation as well. In other words, MultiMediaCard forward compatibility was kept.
Actually the main difference between SD Memory Card and MultiMediaCard is the initialization process.
The SD Memory Card Specifications were divided to several documents. The SD Memory Card
documentation structure is given in Figure 1