AP-SAFD254QA032GS-ETHT Apacer, AP-SAFD254QA032GS-ETHT Datasheet - Page 27

• Manufacturer Part Number: AP-SAFD254QA032GS-ETHT
• Description: Solid State Drives - SSD SAFD 254 SATA FLASH DRIVE SLC 32GB EXT
• Manufacturer: Apacer

Specifications of AP-SAFD254QA032GS-ETHT

• Rohs: yes
• Product: SATA Flash Drives
• Memory Size: 32 GB
• Sustained Read: 163 MB/s
• Sustained Write: 53 MB/s
• Active Mode Current: 400 mA
• Operating Supply Voltage: 5 V
• Maximum Operating Temperature: + 70 C
• Connector Type: 7-pin signal, 15-pin power
• Dimensions: 100 mm x 69.85 mm x 9.3 mm
• Minimum Operating Temperature: 0 C

3. Flash Management
3.1
The SAFD254 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 SAFD254’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.
3.5
Accomplished by the Secure Erase (SE) command, which added to the open ANSI standards that control disk
drives, “Quick Erase” is built into the disk drive itself and thus far less susceptible to malicious software
attacks than external software utilities. It is a positive easy-to-use data destroy command, amounting to
electronic data shredding. Executing the command causes a drive to internally completely erase all possible
user data. This command is carried out within disk drives, so no additional software is required. Once
executed, neither data nor the erase counter on the device would be recoverable, which blurs the accuracy of
device lifespan. The process to erase will not be stopped until finished while encountering power failure, and
will be continued when power is back on.
©2011 Apacer Technology Inc.
Error Correction/Detection
Bad Block Management
Wear Leveling
Power Failure Management
Quick Erase
AP-SAFD254QAxxxxS-XXHT
Serial ATA Flash Drive
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Rev. 1.5