关于nand ecc？

quwer

关于nand ecc？ [复制链接]

常见ecc 源码中：
static const u_char nand_ecc_precalc_table[] =
　　{
　　　　0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
　　　　0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
　　　　0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
　　　　0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
　　　　0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
　　　　0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
　　　　0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
　　　　0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
　　　　0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
　　　　0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
　　　　0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
　　　　0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
　　　　0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
　　　　0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
　　　　0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
　　　　0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
　　};

static void nand_trans_result (u_char reg2, u_char reg3, u_char *ecc_code)
{       u_char a, b, i, temp1, temp2;
        a = b = 0x80;
        temp1 = temp2 = 0;
        
                for (i = 0; i < 4; i++)
                {
         if (reg3 & a)
                    temp1 |= b;   //15,13,11,9bit->ecc_code
             b>>=1;
             if (reg2 & a)
                    temp1 |= b;   //14,12,10,8bit->ecc_code
             b>>=1;
             a>>=1;
                }

        b=0x80;
                for (i = 0; i<4; i++)
                {
                 if (reg3 & a)
                    temp2 |= b;   //7,5,3,1bit->ecc_code
             b>>=1;
             if (reg2 & a)
                    temp2 |= b;   //6,4,2,0bit->ecc_code
             b>>=1;
             a>>=1;
                }

                ecc_code[0] = temp1;
        ecc_code[1] = temp2;
}

//　Calculate 3 byte ECC code for 256 byte block
        void nand_calculate_ecc (const u_char *dat, u_char *ecc_code)
        {
                u_char idx, reg1, reg2, reg3;
                int j;
        /* Initialize variables */
                reg1 = reg2 = reg3 = 0;
                ecc_code[0] = ecc_code[1] = ecc_code[2] = 0;
        /* Build up column parity */
                for (j=0; j<256; j++)
                {
                        /* Get CP0 - CP5 from table */
            idx = nand_ecc_precalc_table[dat[j]];
                        reg1 ^= (idx & 0x3f);
            /* All bit XOR = 1 ? */
                        if (idx & 0x40) {
                                reg3 ^= (u_char) j;
                                reg2 ^= ~((u_char) j);
                        }
                }
        /* Create non-inverted ECC code from line parity */
                nand_trans_result(reg2, reg3, ecc_code);
        /* Calculate final ECC code */
                ecc_code[0] = ~ecc_code[0];
                ecc_code[1] = ~ecc_code[1];
                ecc_code[2] = ((~reg1) << 2) | 0x03;
        }

其中 是怎么检验256byte数据的？  是红色字体dat[j]中吗  请高手赐教 谢谢

yza223

nand_calculate_ecc好像只是计算ECC
并没有校验吧？

注：
/**
* nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code for 256 byte block
* @mtd:        MTD block structure
* @dat:        raw data
* @ecc_code:        buffer for ECC
*/