SDSDM-256 datasheet(9/40 Pages) ETC2

9 / 40 page

1-3

Rev. 2.2, 06/07

SanDisk SD Card Product Family Product Manual

Introduction

Functional Description

The family of SanDisk SD cards contains a high-level, intelligent subsystem as shown in

Figure 1-1. 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

Technology Independence

The 512-byte sector size of a card in the SanDisk SD 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 SD 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 SD 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.

Defect and Error Management

The SanDisk SD 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 SD 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. The SanDisk SD Card Product Family soft error rate

specification is much better than the magnetic disk drive specification. In the extremely rare

case that a read error does occur, SanDisk SD Card Product Family has innovative algorithms

to recover the data. These defect and error management systems, coupled with the solid state

construction, give SanDisk SD Card Product Family unparalleled reliability.

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 SD Card Product Family operate in the data transfer mode.

An authentication procedure is done between a card and the connected device, either the LCM

(PC for example) or the PD (portable device, such as SD player). After the authentication

process passes, the card is ready to accept or give data from/to the connected device. While the

card is in the secured mode of operation (after the authentication succeeded) the argument and

the associated data that is sent to the card or read from the card are encrypted. At the end of

read, write or erase operations, a card automatically gets out of its secured mode.

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