Datasheet

T
T
T
S
S
S
2
2
2
G
G
G
~
~
~
1
1
1
6
6
6
G
G
G
C
C
C
F
F
F
X
X
X
5
5
5
0
0
0
0
0
0
CFast Card
Transcend Information Inc.
V0.5
7
Reliability
Wear-Leveling algorithm
The controller supports static/dynamic wear leveling. When the host writes data, the controller will find and use the block
with the lowest erase count among the free blocks. This is known as dynamic wear leveling. When the free blocks' erase
count is higher than a threshold value plus data blocks', it will activate the static wear leveling, replacing the not so
frequently used user blocks with the high erase count free blocks.
ECC algorithm
Using 8bit BCH Error Correction Code with each channel, the controller can correct 8 random bits per 512 byte data
sector for SLC NAND flash. The hardware executes parity generation and error detection/correction features.
StaticDataRefresh Technology
Normally, ECC engine corrections are taken place without affecting the host normal operations. As time passes by, the
number of error bits accumulated in the read transaction exceeds the correcting capability of the ECC engine, resulting
in corrupted data being sent to the host. To prevent this, the controller monitors the error bit levels at each read
operation; when it reaches the preset threshold value, the controller automatically performs data refresh to “restore” the
correct charge levels in the cell. This implementation practically restores the data to its original, error-free state, and
hence, lengthening the life of the data.
EarlyRetirement Technology
The StaticDataRefresh feature functions well when the cells in a block are still healthy. As the block ages over time, it
cannot reliably store charge anymore, EarlyRetirement enters the scene. EarlyRetirement works by moving the static
data to another block (a health block) before the previously used block becomes completely incapable of holding
charges for data. When the charge loss error level exceeds another threshold value (higher from that for
StaticDataRefresh), the controller automatically moves its data to another block. In addition, the original block is then
marked as a bad block, which prevents its further use, and thus the block enters the state of “EarlyRetirement.”
Note that, through this process, the incorrect data are detected and effectively corrected by the ECC engine, thus the
data in the new block is stored error-free.