The flash translation layer is an additional software layer between the file system and the
NAND flash memory (see Figure 1), which allows operating systems to read and write to
NAND flash memory devices in the same way as disk drives. It provides the translation from
virtual to physical addresses and includes wear leveling and garbage collection software
modules, which it calls when required.
NAND flash memories have relatively long erase times, as erase operations are done one
block at a time. With the flash translation layer this long erase time becomes transparent,
because instead of erasing a block to be able to rewrite it, the FTL simply writes the data to
another physical page and marks the data contained in the previous physical page as
invalid.
The garbage collection module is used to free this invalid memory space to allow further
program operations.
Refer to single level cell, and multilevel cell large page NAND flash memory datasheets for
the full list of NAND flash memories covered by this application note and for further