MD2241-D128-V3 M-Systems Inc., MD2241-D128-V3 Datasheet - Page 23

• Manufacturer Part Number: MD2241-D128-V3
• Description: Diskonchip Dimm Plus
• Manufacturer: M-Systems Inc.

Static Wear-Leveling
Areas on the flash media may contain static files, characterized by blocks of data that remain unchanged for very
long periods of time, or even for the whole device lifetime. If wear-leveling were only applied on newly written
pages, static areas would never be cycled. This limited application of wear-leveling would lower life expectancy
significantly in cases where flash memory contains large static areas. To overcome this problem, TrueFFS forces
data transfer in static areas as well as in dynamic areas, thereby applying wear-leveling to the entire media.
6.1.6 Power Failure Management
TrueFFS uses algorithms based on “erase after write” instead of "erase before write" to ensure data integrity during
normal operation and in the event of a power failure. Used areas are reclaimed for erasing and writing the flash
management information into them only after an operation is complete. This procedure serves as a check on data
integrity.
The “erase after write” algorithm is also used to update and store mapping information on the flash memory. This
keeps the mapping information coherent even during power failures. The only mapping information held in RAM is
a table pointing to the location of the actual mapping information. This table is reconstructed during power-up or
after reset from the information stored in the flash memory.
To prevent data from being lost or corrupted, TrueFFS uses the following mechanisms:
6.1.7 Error Detection/Correction
TrueFFS implements a Reed-Solomon Error Correction Code (ECC) algorithm to ensure data reliability. Refer to
section 3.5 for further information on the EDC/ECC mechanism.
6.1.8 Special Features through I/O Control (IOCTL) Mechanism
In addition to standard storage device functionality, the TrueFFS driver provides extended functionality. This
functionality goes beyond simple data storage capabilities to include features such as: format the media, read/write
protect, binary partition(s) access, flash defragmentation and other options. This unique functionality is available in
all TrueFFS-based drivers through the standard I/O control command of the native file system.
For further information, please refer to application note AP-DOC-046 Extended Functions of TrueFFS Driver for
DiskOnChip.
6.1.9 Compatibility
The TrueFFS driver supports all released DiskOnChip products. Upgrading from one product to another requires no
additional software integration.
When using different drivers (e.g. TrueFFS SDK, Boot SDK, BIOS extension firmware, etc.) to access DiskOnChip
DIMM Plus, the user must verify that all software is based on the same code base version. It is also important to use
only tools (e.g. DFORMAT, DINFO, GETIMAGE, etc.) derived from the same version as the firmware version and
the TrueFFS drivers used in the application. Failure to do so may lead to unexpected results, such as lost or
corrupted data. The driver and firmware version can be verified by the sign-on messages displayed, or by the version
information stored in the driver or tool.
Note: When a new M-Systems’ DiskOnChip product with new features is released, a new TrueFFS version is
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required.
When writing, copying, or erasing the flash device, the data format remains valid at all intermediate stages.
Previous data is never erased until the operation has been completed and the new data has been verified.
A data sector cannot exist in a partially written state. Either the operation is successfully completed, in
which case the new sector contents are valid, or the operation has not yet been completed or has failed, in
which case the old sector contents remain valid.
Preliminary Data Sheet, Rev. 1.2
DiskOnChip DIMM Plus
94-SR-002-08-8L