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How does NAND flash controller work?
Flash controllers manage the data stored on NOR and NAND flash memory, and they communicate with the computer or device. After a flash device is made, the controller formats the flash memory to ensure the device works properly. It maps flash cells and determines which spare cells will replace any failed ones.
When NAND flash memory is erased all bits are set to 1?
Flash Basics The NAND Flash array is grouped into a series of blocks, which are the smallest erasable entities in a NAND Flash device. A NAND Flash block is 128KB. Erasing a block sets all bits to 1 (and all bytes to FFh).
How does an erase operation on a flash chip work?
An erase operation on a flash chip clears the data from all pages in the block, so if some of the other pages contain active data (stuff you want to keep) you either have to copy it elsewhere first or hold off from doing the erase.
What happens when a NAND flash page is empty?
[* Technical note: Ok so actually when a NAND flash page is empty it is all binary ones, e.g. 11111111. A program operation sets any bit with the value of 1 to 0, so for example 11111111 could become 11110000. This means that later on it is still possible to perform another program operation to set 11110000 to 00110000 for example.
Why does NAND erase only at block level and not page level?
The reason is that the smaller the block, the larger the penalty in transistors and die area, which increases costs. While smaller blocks are easier to use and faster to erase, they are more costly in terms of die size, so every blocking scheme must balance its block sizes with device cost and the needs of its target application…”
What happens when you erase a block in Flash?
If you were to erase the block every time you wanted to change the contents of a page, your flash would wear out very quickly. So a far better alternative is to simply mark the old page (containing the unchanged data) as INVALID and then write the new, changed data to an empty page.