SD card

4.3 SD card

The Secure Digital Card is a flash-based memory card that is specifically designed to meet the security, capacity, performance and environmental requirements inherent in newly emerging audio and video consumer electronic devices. The SD Card includes a copyright protection mechanism that complies with the security of the SDMI standard, and is faster and capable of higher Memory capacity. The SD Card security system uses mutual authentication and a “new cipher algorithm” to protect from illegal usage of the card content. A non-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 SD Card, with some additions.

The SD Card communication is based on an advanced nine-pin interface (Clock, Command, 4xData and 3xPower lines) designed to operate in a low voltage range. The communication protocol is defined as part of this specification. The SD Card host interface supports regular Multimedia Card operation as well. In other words,

Multimedia Card forward compatibility was kept. Actually the main difference between SD Card and Multimedia Card is the initialization process. The SD Card specifications were originally defined by MEI (Matsushita Electric Company), Toshiba Corporation and SanDisk Corporation. Currently, the specifications are controlled by the Secure Digital Association (SDA), the SanDisk SD Card was designed to be compatible with the SD Card Physical Specification. The SD Card interface allows for easy integration into any design, regardless of microprocessor used. For compatibility with existing controllers, the SanDisk SD Card offers, in addition to the SD Card interface, an alternate communication protocol, which is based on the SPI standard. The current SD Card provides up to 1024 million bytes of memory using flash memory chips, which were designed especially for use in mass storage applications. In addition to the mass storage specific flash memory chip, the SD Card includes an on-card intelligent controller which manages interface protocols, security algorithms for copyright protection, data storage and retrieval, as well as Error Correction Code (ECC) algorithms, defect handling and diagnostics, power management and clock control.