Error Correction Code Computation Ecc (Nand Flash); Nand Flash/Pc Card Controller Registers - ST STM32F102 Series Reference Manual

RM0008
18.6.5

Error correction code computation ECC (NAND Flash)

The FSMC PC-Card controller includes two error correction code computation hardware
blocks, one per memory bank. They are used to reduce the host CPU workload when
processing the error correction code by software in the system.
These two registers are identical and associated with bank 2 and bank 3, respectively. As a
consequence, no hardware ECC computation is available for memories connected to bank
4.
The error correction code (ECC) algorithm implemented in the FSMC can perform 1-bit error
correction and 2-bit error detection per 256, 512, 1 024, 2 048, 4 096 or 8 192 bytes read
from or written to NAND Flash.
The ECC modules monitor the NAND Flash databus and read/write signals (NCE and NWE)
each time the NAND Flash memory bank is active.
The functional operations are:
●
When access to NAND Flash is made to bank 2 or bank 3, the data present on the
D[15:0] bus is latched and used for ECC computation.
●
When access to NAND Flash occurs at any other address, the ECC logic is idle, and
does not perform any operation. Thus, write operations for defining commands or
addresses to NAND Flash are not taken into account for ECC computation.
Once the desired number of bytes has been read from/written to the NAND Flash by the
host CPU, the FSMC_ECCR2/3 registers must be read in order to retrieve the computed
value. Once read, they should be cleared by resetting the ECCEN bit to zero. To compute a
new data block, the ECCEN bit must be set to one in the FSMC_PCR2/3 registers.
18.6.6

NAND Flash/PC Card controller registers

PC Card/NAND Flash control registers 2..4 (FSMC_PCR2..4)
Address offset: 0xA0000000 + 0x40 + 0x20 * (x – 1), x = 2..4
Reset value: 0x0000 0018
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
Res.
Flexible static memory controller (FSMC)
r/w r/w
9 8 7 6 5
r/w r/w r/w r/w
4 3 2 1 0
r/w r/w r/w Res
405/690