SQFlash
Industrial Class 10 Micro SD Card
Specifications subject to change without notice, contact your sales representatives for the most update information.
REV 0.3 Page 8 of 22 May. 4, 2016
4. Flash Management
Error Correction Code (ECC)
Flash memory cells will deteriorate with use, which might generate random bit errors in the stored data. Thus,
SQF-MSD applies the BCH ECC algorithm, which can detect and correct errors occur during read process,
ensure data been read correctly, as well as protect data from corruption.
Wear Leveling
NAND Flash devices can only undergo a limited number of program/erase cycles, and in most cases, the
flash media are not used evenly. If some area get updated more frequently than others, the lifetime of the
device would be reduced significantly. Thus, Wear Leveling technique is applied to extend the lifespan of
NAND Flash by evenly distributing write and erase cycles across the media.
SQF-MSD provides advanced Wear Leveling algorithm, which can efficiently spread out the flash usage
through the whole flash media area. Moreover, by implementing both dynamic and static Wear Leveling
algorithms, the life expectancy of the NAND Flash is greatly improved.
Bad Block Management
Bad blocks are blocks that include one or more invalid bits, and their reliability is not guaranteed. Blocks that
are identified and marked as bad by the manufacturer are referred to as “Initial Bad Blocks”. Bad blocks that
are developed during the lifespan of the flash are named “Later Bad Blocks”. SQF-MSD implements an
efficient bad block management algorithm to detect the factory-produced bad blocks and manages any bad
blocks that appear with use. This practice further prevents data being stored into bad blocks and improves
the data reliability.
Auto-Read Refresh
Auto-Read Refresh is specifically applied on devices that read data mostly but rarely write data, such as GPS.
When blocks are continuously read, then the device cannot activate wear leveling since it can only be applied
while writing data. Thus, errors will accumulate and become uncorrectable. Accordingly, to avoid errors
exceed the amount ECC can correct and blocks turn bad, The firmware of SQF-MSD will automatically
refresh the bit errors when the error number in one block approaches the threshold, ex., 24 bits.
