User Manual

Introduction to the TriFlash with SD Interface

1.5.1. Flash Technology Independence

The 512-byte sector size of the TriFlash is the same as that in an IDE magnetic disk drive. To write or read a sector

(or multiple sectors), the host computer software simply issues a Read or Write command to the TriFlash. This

command contains the address. 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

as flash devices are expected to get more and more complex in the future. Because the TriFlash uses an intelligent

on-board controller, the host system software will not require changing as new flash memory evolves. In other

words, systems that support the TriFlash today will be able to access future SanDisk TriFlash devices built with new

flash technology without having to update or change host software.

1.5.2. Defect and Error Management

The TriFlash 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. For instance, disk drives do not typically

perform a read after write to confirm the data is written correctly because of the performance penalty that would be

incurred. The TriFlash does a read after write under margin conditions to verify that the data is written correctly. In

the rare case that a bit is found to be defective, the TriFlash replaces this bad bit with a spare bit within the sector

header. If necessary, the TriFlash will even replace the entire sector with a spare sector. This is completely

transparent to the host and does not consume any user data space.

The TriFlash device’s soft error rate specification is much better than the magnetic disk drive specification. In the

extremely rare case a read error does occur, the TriFlash has innovative algorithms to recover the data. This is

similar to using retries on a disk drive but is much more sophisticated. The last line of defense is to employ a

powerful ECC to correct the data. If ECC is used to recover data, defective bits are replaced with spare bits to

ensure they do not cause any future problems.

These defect and error management systems coupled with the solid-state construction give the TriFlash unparalleled

reliability.

1.5.3. Endurance

The SanDisk TriFlash has an endurance specification for each sector of 300,000 or 100,000 writes (reading a logical

sector is unlimited) under typical conditions (depending on the model, refer to Table 2-4). This is far beyond what is

needed in nearly all applications of TriFlash devices. Even very heavy use of the TriFlash in cellular phones,

personal communicators, pagers and voice recorders will use only a fraction of the total endurance over the typical

device’s five year lifetime. For instance, it would take over 34 years to wear out an area on the TriFlash on which a

file of any size (from 512 bytes to capacity) was rewritten 3 times per hour, 8 hours a day, 365 days per year.

With typical applications, the endurance limit is not of any practical concern to the vast majority of users.

1.5.4. Wear Leveling

The SanDisk TriFlash does not require or perform a Wear Level operation.