Datasheet

More Functions to extend product life
1. Global Wear Leveling – Advanced algorithm to enhance the Wear-Leveling Efficiency
There are 3 main processes in global wear leveling approaches:
(1) Record the block erase count and save in the wear-leveling table.
(2) Find the static-block and save it in wear-leveling pointer.
(3) Check the erase count when the block popped from spare pool. If the block erase count is bigger than
WEARCNT, then swapped the static-block and over-count-block.
After actual test, global wear leveling successfully even the erase count of every block; hence, it can
extend the life expectancy of Flash product.
2. StaticDataRefresh Technology – Keeping Data Healthy
There are many variants that would disturb the charge inside a Flash cell. These variants can be: time, read
operations, undesired charge, heat, etc; each variant would create a charge loss, and the contents shift in their
charge levels slightly. In our everyday usage – more than 60% are repeated read operations, the accumulated
charge loss would eventually result in the data loss.
Normally, ECC engine corrections are taken place without affecting the host normal operations. As time
passes by, the number of error bits ac cumulated in the read transaction exceeds the correcting capability of the
ECC engine, resulting in corrupted data being sent to the host.
To prevent this, Transcend’s CF300 monitor the error bit levels at each r ead 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 t o its original, error-free state, and hence, lengthening
the life of the data.
3. EarlyRetirement – Avoiding Data Loss Due to Weak Block
The StaticDataRefresh feature functions well when the cells in a block are still healthy. As the block ages
over time, it cannot store charge reliably 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, t hrough 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.
4. Advanced Power Shield – Avoiding Data Loss during Power Failure
When a power failure takes place, the line voltage drops. When it reaches the first Logic-Freeze Threshold,
the
core controller is held at a steady state. Here are some implications. First, it ceases the communication with
the
host. This prevents the host from s ending in further address /instructions/data that may be corrupted. During
power
disturbance, the host is likely experiencing a voltage drop, so the transmission integrity cannot be
guaranteed.
Second, it stops the information sending to the Flash. This prevents the controller from corrupting the
address/data
being transmitted to the Flash, and corrupting the Flash contents inadvertently.
Further more, Advanced Power Shield cut off the connection bet ween host power and turn off the controller
to
reserve most of the energy for NAND Flash to complete programming.