ST72682 datasheet(13/36 Pages) STMICROELECTRONICS

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ST72682

NAND Flash memory interface

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4.1

NAND Flash error correction

No NAND Flash memory arrays are guaranteed by manufacturers to be error-free. Error

occurrence depends on the Flash cell type (MLC or SLC).

The ST72682 embeds hardware and firmware mechanisms to correct the errors.

4.1.1

Hardware error correction

The ST72682 embeds a Reed-Solomon algorithm-based hardware cell. This cell directly

manages 512-byte data packets on the NAND I/O system.

Based on the data packet content, the cell generates an 80-bit Error Correction Code (ECC)

consisting of 8 words, each containing 10 bits.

During write operations to NAND memory, the 512-bytes of data and the ECC are stored

together in the same page. The ECC is stored in the corresponding Redundant Area (RA),

using 10 bytes.

During read operations, the 512-bytes of data and the 8 ECC words are read back and are

passed through the Reed-Solomon cell for decoding. The cell allows the correction of 4

symbols in this 520-symbol packet (512 symbols from data + 8 symbols from ECC).

The hardware cell gives three possible results:

■

No error detected: the data packet can be used as it is.

■

Correctable error detected: the corrected data are available in a specific 512-byte buffer

in the Reed-Solomon cell and are ready to be used.

■

Uncorrectable error detected: data corruption cannot be repaired.

4.1.2

Firmware error management

The firmware defines the error correction possibilities with the corrected data packet.

When data cannot be repaired, the block is considered as a bad block and is replaced by

another one. See Section 4.2 for further information on bad block management.

NAND Flash part number

NAND Flash size (Mbytes or

Gbytes) and type

Number of NAND Flash devices supported

ST72682/R20 device

ST72682/R21 device

Hynix HY27UH088G2M

1 GB; SLC2K; Single CE

1, 2, 4, 6 or 8

Hynix HY27UT084G2M

512 MB; MLC2K; Single CE

1, 2, 4, 6 or 8

Hynix HY27UU088G5M

1 GB; MLC2K; Dual CE

2 or 4

1, 2 or 4

Micron 29F2G08AA

256 MB; SLC2K; Single CE

1, 2, 4, 6 or 8

Micron 29F4G08BA

512 MB; SLC2K; Single CE

1, 2, 4, 6 or 8

Micron 29F8G08FA

1 GB; SLC2K; Dual CE

2 or 4

1, 2 or 4

Table 7.

Known NAND Flash memory compatibility guide for ST72682/R20 and ST72682/R21

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