RAM 6.0 BUX II Series Guía de usuario descargar pdf (Pagina 27)

8. Flash Devices and Flash File System Support

8.2 Choosing TrueFFS as a Medium

TrueFFS applications can read and write from flash memory just as they would

from an MS-DOS file system resident on a magnetic-medium mechanical disk

drive. However, the underlying storage media are radically different. While these

differences are generally transparent to the high-level developer, it is critical that

you be aware of them when designing an embedded system.

Flash memory stores data indefinitely, even while power is removed. The physical

components of flash memory are solid-state devices—that is, devices with no

moving parts—that consume little energy and leave a small foot print. Thus, flash

memory is ideal for mobile devices, for hand-held devices, and for embedded

systems that require reliable, non-volatile environments that are too harsh for

mechanical disks.

Flash has a limited life due to the finite number of erase cycles. TrueFFS only

supports flash devices that are symmetrically blocked. In addition, some features

common to block device drivers for magnetic media are not available with flash

memory. Unequal read and write time is a typical characteristic of flash memory,

in which reads are always faster than writes. For more information, see

Wear-Leveling, p.27.

The unique qualities that distinguish flash memory from magnetic-media disk

drives make it an ideal choice for some types of applications, yet impractical for

others.

8.3 TrueFFS Features

This section discusses flash memory functionality, and the ways in which it

protects data integrity, extends the lifetime of the medium, and supports fault

recovery.

NOTE: Although you can write in any size chunks of memory, ranging from bytes

to words and double words, you can only erase in blocks. The best approach to

extending the life of the flash is to ensure that all blocks wear evenly. For more

information, see Wear-Leveling, p.27.

NOTE: The TrueFFS optional product does have not support for partition tables.

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RAM 6.0 BUX II Series Guía de usuario Pagina 27