UM0851 datasheet(131/245 Pages) STMICROELECTRONICS

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UM0851

Non-volatile memory device drivers

Doc ID 16604 Rev 2

131/245

nand_scan().This activates the default Flash based bad block table functionality of the

NAND driver. The default bad block table options are:

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Store bad block table per chip

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Use 2 bits per block

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Automatic placement at the end of the chip

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Use mirrored tables with version numbers

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Reserve 4 blocks at the end of the chip

User defined tables

User defined tables are created by filling out a struct nand_bbt_descr and storing the pointer

in the struct nand_chip member bbt_td before calling nand_scan(). If a mirror table is

necessary a second structure must be created and a pointer to this structure must be stored

in bbt_md inside the struct nand_chip. If the bbt_md member is set to NULL then only the

main table is used and no scan for the mirrored table is performed.

The struct nand_bbt_descr is the descriptor for the bad block table marker and the

descriptor for the pattern which identifies good and bad blocks. The assumption is made

that the pattern and the version count are always located in the oob area of the first block.

struct nand_bbt_descr {

int options;

options for this descriptor

int * pages;

the page(s) where we find the bbt, used with option BBT_ABSPAGE when bbt is

searched, then we store the found bbts pages here. Its an array and supports

up to 8 chips now

int offs;

offset of the pattern in the oob area of the page

int veroffs;

offset of the bbt version counter in the oob are of the page

uint8_t * version;

version read from the bbt page during scan

int len;

length of the pattern, if 0 no pattern check is performed

int maxblocks;

maximum number of blocks to search for a bbt. This number of blocks is

reserved at the end of the device where the tables are written.

int reserved_block_code;

if non-0, this pattern denotes a reserved (rather than bad) block in the

stored bbt

uint8_t * pattern;

pattern to identify bad block table or factory marked good / bad blocks, can

NULL, if len = 0

};

Error correcting code (ECC)

To manage ECC, the NAND driver must provide the following functions:

●

enable_hwecc(): this function is called before reading/writing to the chip. It resets or

initializes the hardware ECC generator in this function. The function is called with an

UM0851 Datasheet(PDF) 131 Page - STMicroelectronics

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