101-1104 Rabbit Semiconductor, 101-1104 Datasheet - Page 4

• Manufacturer Part Number: 101-1104
• Description: MEMORY CARD READER USB REMOVABLE
• Manufacturer: Rabbit Semiconductor

Specifications of 101-1104

• Accessory Type: USB Removable Memory Card Reader
• For Use With/related Products: Rabbit-based Boards
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

IMPORTANT INFORMATION FOR RABBIT DEVELOPERS
Partitions
The USB memory card reader works only with a one-partition memory card.
Wear Reduction
One of the ways that the Dynamic C FAT file system reduces flash wear is to use
the 16K erase block size for the cluster size. This prevents files from sharing
erase units, and means that the smallest block of flash a file can use is 16K. Keep
this in mind when designing FAT applications.
Caching and Power Failure
RabbitCore modules and Rabbit-based single-board computers using the
Dynamic C FAT file system with memory cards do caching in battery-backed
RAM as a way of reducing wear and to provide extra safety against data loss in
the event of unexpected power cycling or card removal. The card reader doesn’t
do any caching. A power failure during a file-write operation to the memory card
could therefore result in loss of all files on the card. The easiest way to prevent
critical data loss from such a power failure is to use a laptop with a charged
battery that will continue running if AC power cuts out. It is also suggested that
existing critical data on a card be copied to the PC for backup before doing a
file-write to the memory card. File-read operations will not corrupt the memory
card.
Unique Volume Labels
Partitions created using the
function call from the Dynamic C
fat_autoMount()
FAT file system have unique volume labels so that cache recovery operations are
not attempted on a memory card that was not the one being used when a power
failure or premature card removal occurred. The system timer is used as a
random seed to create unique labels. Because the memory card reader has no
battery-backed real-time clock, the reader uses factory-bad NAND blocks for
entropy to create a random seed. It also uses a loop counter that runs on start-up
while waiting for a card to be inserted. To minimize the chances of the same
random label being created twice, format new cards by plugging in the card
reader without a memory card, then insert the card.
Firmware Upgrades
Assuming the firmware is intact and the hardware undamaged, the card reader
firmware can be upgraded by simply by inserting a memory card with a firmware
update file on it and plugging the reader into a USB slot. Check the Rabbit
Semiconductor Web site for firmware upgrades and instructions.
020-0094 • 060912–C