请教：C6747的nand flash控制器的4-bit ECC不正常，请帮分析一下问题

我好像没有注意到TI提供的NAND例程里有4bit ECC的，你是自己写的么（也有可能有我没注意到）？

如果是自己写的，是否注意到NAND ECC操作的流程呢：

the 4BITECC_ADD_CALC_START bit in the NAND Flash control register (NANDFCR) to 1.
10. Start another read from NAND, if required (a new thread from step 1).
11. Wait for the 4-bit ECC correction state field (ECC_STATE) in the NAND Flash status register
(NANDFSR) to be equal to 1, 2h, or 3h.
12. The number of errors can be read from the 4-bit number of errors field (ECC_ERRNUM) in the NAND
Flash status register (NANDFSR).
13. Read the error address from the NAND Flash error address 1-2 registers (NANDERRADD[2:1]).
Address for the error word is equal to (total_words_read + 7 - address_value). For 518 bytes, the
address will be equal to (525 - address_value).
14. Read the error value from the NAND Flash error value 1-2 registers (NANDERRVAL[2:1]). Errors can
be corrected by XORing the error word with the error value from the NAND Flash error value 1-2
registers (NANDERRVAL[2:1]).