SanDisk 4GB micro SDHC Memory Card for Product Manual - Page 8

SanDisk microSD™, microSDHC™ and microSDXC™ cards OEM Product Manual 2.5 1.5 Functional Description The family of SanDisk microSD cards contains a high-level, intelligent subsystem as shown in Figure 1. This intelligent (microprocessor) subsystem provides many capabilities not found in other types of memory cards. These capabilities include: • Host independence from details of erasing and programming flash memory • Sophisticated system for managing defects (analogous to systems found in magnetic disk drives) • Sophisticated system for error recovery including a powerful ECC • Power management for low power operation 1.5.1 Technology Independence The 512-byte sector size of a card in the SanDisk microSD Card Product Family is the same as that in an IDE magnetic disk drive. To write or read a sector (or multiple sectors), the host software simply issues a read or write command to the card. The command contains the address and number of sectors to write or read. The host software then waits for the command to complete. The host software does not get involved in the details of how the flash memory is erased, programmed or read. This is extremely important because flash devices are expected to get increasingly complex in the future. Because cards in the SanDisk microSD Card Product Family use an intelligent on-board controller, host system software will not need to be updated as new flash memory evolves. In other words, systems that support the microSD Card Product Family today will be able to access future SanDisk cards built with new flash technology without having to update or change host software. 1.5.2 Defect and Error Management The SanDisk microSD Card Product Family contains a sophisticated defect and error management system. This system is analogous to the systems found in magnetic disk drives and in many cases offers enhancements. If necessary, SanDisk microSD Card Product Family will rewrite data from a defective sector to a good sector. This is completely transparent to the host and does not consume any user data space.. In the extremely rare case that a read error does occur, SanDisk microSD Memory Card Product Family has innovative algorithms to recover the data. These defect and error management systems, coupled with the solid state construction, give SanDisk microSD Card Product Family enormous reliability. 1.5.3 Content Protection A detailed description of the content protection mechanism and related security SD commands can be found in the SD Security Specification from the SDA. All SD security-related commands in the SanDisk microSD Card Product Family operate in the data transfer mode. 1.5.4 Wear Leveling Wear leveling is an intrinsic part of the erase pooling functionality of cards in the SanDisk microSD Card Product Family using NAND memory. 1.5.5 Automatic Sleep Mode A unique feature of cards in the SanDisk microSD Card Product Family is automatic entrance and exit from sleep mode. Upon completion of an operation, cards enter January 2012 Version 2.5 © 2008 - 2012 SanDisk Corporation. SanDisk Confidential, subject to all applicable non-disclosure agreements 3