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Flash Memory Block Device Driver
ponent TrueFFS
Introduction
TrueFFS for Tornado is an optional product that provides a block device interface to a
wide variety of flash memory devices. TrueFFS is a patible
implementation of M-Systems FLite, version . This system is reentrant, thread-safe,
and supported on all CPU architectures that host VxWorks.
This chapter begins with a brief introduction to flash memory, followed by a step-by-
step outline of the procedure for building a system with TrueFFS. Then, the main part of
the chapter describes these steps in detail, including sections devoted to writing your
own socket driver and ponents. The chapter ends with a description of the
functionality of flash memory block devices.
NOTE: This version of the TrueFFS product is a block device driver to VxWorks that,
although intended to be file system neutral, is guaranteed to work only with the MS-DOS
compatible file system offered with this product.
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 ic-medium mechanical disk drive. However,
the underlying storage media are radically different. While these differences are
completely 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 unpowered. The ponents
of flash memory are solid-state devices1 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.
However, flash does have a limited life, due to the finite number of erase cycles; and,
TrueFFS only supports flash devices that are symmetrically blocked. In addition, some