SanDisk SD25B-100, Product Manual

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FlashDrive Product Manual
FlashDrive Product Manual © 1999 SANDISK CORPORATION 10
is used to recover data, defective bits are replaced
with spare bits to ensure they do not cause future
problems.
These defect and error management systems
coupled with the solid-state construction give the
FlashDrives unparalleled reliability.
1.5.3 Endurance
Even very heavy use of the FlashDrive in a
computer system will use only a fraction of the
total endurance over the computer’s five year
lifetime. For instance, it would take over 34 years
to wear out an area on the drive on which a file of
any size (from 512 bytes to drive capacity) was
rewritten 3 times per hour, 8 hours a day, 365 days
per year.
With typical applications (PIM software, word
processing, spreadsheets, data collection, etc.),
the 300,000 endurance limit is not of any practical
concern to the vast majority of users.
1.5.4 Wear Leveling
The FlashDrives do not require or perform a Wear
Level operation. The command is supported as a
NOP
operation to maintain backward
compatibility with existing software utilities.
1.5.5 Automatic Sleep Mode
A unique feature of the SanDisk FlashDrives is
automatic entrance and exit from sleep mode.
Upon completion of a command, the FlashDrives
will enter the sleep mode to conserve power if no
further commands are received within 5 msec. The
host does not have to take any action for this to
occur. In most systems the FlashDrives are in sleep
mode except when the host is accessing it; thus,
conserving power. Note that the delay from
command completion to entering sleep mode can be
adjusted.
When the host is ready to access the drive and it
is in sleep mode, any command issued to the drive
will cause it to exit sleep and respond. The host
does not have to follow the ATA protocol of
issuing a reset first. It may do this if desired, but
it is not needed. By not issuing the reset,
performance is improved through the reduction of
overhead but this must be done only for the
SanDisk products as other IDE products may not
have this feature.
1.5.6 Power Supply Requirements
This is a dual voltage product which means it
will operate at a voltage range of 3.30 volts ± 5%
or 5.00 volts ± 10% (± 5% for industrial versions).