AP-SDM008GAPANS-B Apacer, AP-SDM008GAPANS-B Datasheet - Page 32

• Manufacturer Part Number: AP-SDM008GAPANS-B
• Description: Memory Modules SDM II 8GB
• Manufacturer: Apacer

Specifications of AP-SDM008GAPANS-B

• Product: 2.5 in Solid State Drive
• Operating Supply Voltage: 5 V
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Memory Size: 8 GB
• Memory Type: SATA Disk Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3. Flash Management
3.1
The SDM implements a hardware ECC scheme, based on the BCH algorithm. It can detect and correct up to
8 bits or 15 bits error in 512 bytes.
3.2
Although bad blocks on the flash media are already identified by the flash manufacturer, they can also be
accumulated over time during operation. The SDM’s controller maintains a table that lists those normal blocks
with disk data, the free blocks for wear leveling, and bad blocks with errors. When a normal block is detected
broken, it is replaced with a free block and listed as a bad block. When a free block is detected broken, it is
then removed from the free block list and marked as a bad block.
During device operation, this ensures that newly accumulated bad blocks are transparent to the host. The
device will stop file write service once there are only two free blocks left such that the read function is still
available for copying the files from the disk into another.
3.3
The NAND flash devices are limited by a certain number of write cycles. When using a FAT-based file system,
frequent FAT table updates are required. If some area on the flash wears out faster than others, it would
significantly reduce the lifetime of the whole SSD, even if the erase counts of others are far from the write
cycle limit. Thus, if the write cycles can be distributed evenly across the media, the lifetime of the media can
be prolonged significantly. This scheme is called wear leveling.
Apacer’s wear-leveling scheme is achieved both via buffer management and Apacer-specific static wear
leveling. They both ensure that the lifetime of the flash media can be increased, and the disk access
performance is optimized as well.
3.4
The Low Power Detection on the controller initiates crucial data saving before the power supplied to the
device is too low. This feature prevents the device from crash and ensures data integrity during an
unexpected power-off.
© 2009 Apacer Technology Inc.
Error Correction/Detection
Bad Block Management
Wear Leveling
Power Failure Management
AP-SDMxxxxXPANS-B
SATA-Disk Module
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Rev. 1.0