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Products => Computers => Programming => Topic started by: carver on September 05, 2021, 01:00:04 pm

Title: help calculate Micron NAND on die ECC
Post by: carver on September 05, 2021, 01:00:04 pm
Hi. I can't google how to check ECC in a read NAND image.

NAND chip from Micron, 29F2G16
for READ ID (90h) command gives 2C CA 90 D5 86 00 00 00
according to the PDF, the bits say that 4-bit ECC.
512+4 (data) + 4 (spare/"not_used") + 8 (parity/ECC) bytes
and Internal ECC enabled

an old micron decoder with pudn/google calculate
bch_encoder_0x201b.exe -m 13 -k 4128 -t 4 <noname.txt // -> 07ED34D14242C
bch_encoder_0x25af.exe -m 13 -k 4128 -t 4 <noname.txt // -> EDE66E50C82B7
depending on the polynomial, but not A3BE308501E09E8A as in my dump

below is an example of a sector. maybe someone can help. thanks.

Code: [Select]
00000000  74 65 6d 20 66 6f 75 6e  64 20 61 74 20 62 6c 6f  |tem found at blo|
00000010  63 6b 20 25 64 0a 00 00  3c 35 3e 52 41 4d 44 49  |ck %d...<5>RAMDI|
00000020  53 4b 3a 20 43 6f 75 6c  64 6e 27 74 20 66 69 6e  |SK: Couldn't fin|
00000030  64 20 76 61 6c 69 64 20  52 41 4d 20 64 69 73 6b  |d valid RAM disk|
00000040  20 69 6d 61 67 65 20 73  74 61 72 74 69 6e 67 20  | image starting |
00000050  61 74 20 25 64 2e 0a 00  3c 33 3e 52 41 4d 44 49  |at %d...<3>RAMDI|
00000060  53 4b 3a 20 43 6f 75 6c  64 6e 27 74 20 61 6c 6c  |SK: Couldn't all|
00000070  6f 63 61 74 65 20 67 7a  69 70 20 62 75 66 66 65  |ocate gzip buffe|
00000080  72 0a 00 00 3c 33 3e 52  41 4d 44 49 53 4b 3a 20  |r...<3>RAMDISK: |
00000090  43 6f 75 6c 64 6e 27 74  20 61 6c 6c 6f 63 61 74  |Couldn't allocat|
000000a0  65 20 67 7a 69 70 20 77  69 6e 64 6f 77 0a 00 00  |e gzip window...|
000000b0  62 61 64 20 67 7a 69 70  20 6d 61 67 69 63 20 6e  |bad gzip magic n|
000000c0  75 6d 62 65 72 73 00 00  69 6e 74 65 72 6e 61 6c  |umbers..internal|
000000d0  20 65 72 72 6f 72 2c 20  69 6e 76 61 6c 69 64 20  | error, invalid |
000000e0  6d 65 74 68 6f 64 00 00  49 6e 70 75 74 20 69 73  |method..Input is|
000000f0  20 65 6e 63 72 79 70 74  65 64 00 00 4d 75 6c 74  | encrypted..Mult|
00000100  69 20 70 61 72 74 20 69  6e 70 75 74 00 00 00 00  |i part input....|
00000110  49 6e 70 75 74 20 68 61  73 20 69 6e 76 61 6c 69  |Input has invali|
00000120  64 20 66 6c 61 67 73 00  69 6e 76 61 6c 69 64 20  |d flags.invalid |
00000130  63 6f 6d 70 72 65 73 73  65 64 20 66 6f 72 6d 61  |compressed forma|
00000140  74 20 28 65 72 72 3d 31  29 00 00 00 69 6e 76 61  |t (err=1)...inva|
00000150  6c 69 64 20 63 6f 6d 70  72 65 73 73 65 64 20 66  |lid compressed f|
00000160  6f 72 6d 61 74 20 28 65  72 72 3d 32 29 00 00 00  |ormat (err=2)...|
00000170  6f 75 74 20 6f 66 20 6d  65 6d 6f 72 79 00 00 00  |out of memory...|
00000180  6f 75 74 20 6f 66 20 69  6e 70 75 74 20 64 61 74  |out of input dat|
00000190  61 00 00 00 69 6e 76 61  6c 69 64 20 63 6f 6d 70  |a...invalid comp|
000001a0  72 65 73 73 65 64 20 66  6f 72 6d 61 74 20 28 6f  |ressed format (o|
000001b0  74 68 65 72 29 00 00 00  63 72 63 20 65 72 72 6f  |ther)...crc erro|
000001c0  72 00 00 00 6c 65 6e 67  74 68 20 65 72 72 6f 72  |r...length error|
000001d0  00 00 00 00 52 41 4d 44  49 53 4b 3a 20 69 6d 61  |....RAMDISK: ima|
000001e0  67 65 20 74 6f 6f 20 62  69 67 21 20 28 25 64 4b  |ge too big! (%dK|
000001f0  69 42 2f 25 6c 64 4b 69  42 29 0a 00 2f 69 6e 69  |iB/%ldKiB)../ini|
00000200  ff ff ff ff ff ff ff ff  a3 be 30 85 01 e0 9e 8a  |..........0.....|
Title: Re: help calculate Micron NAND on die ECC
Post by: DavidAlfa on September 05, 2021, 04:10:54 pm
You don't have any ECC algorithm in the nand itself, it only has extra spare space for storing it, and the host writes whatever on it:
Quote
The MT29F2G device contains 2,048 blocks. Each block is subdivided into 64 programmable pages. Each page consists of 2,112 bytes. The pages are further divided into a
2,048-byte data storage region with a separate 64-byte area. The 64-byte area is typically used for error management functions.

Commands don't have ECC.
READ ID is a 5-byte command, so: 2C CA 90 D5 86

Byte 0: Manufacturer ID   0x2C = Micron
Byte 1: Device ID            0xCA = MT29F2G16AAD
...

Only "Read Unique ID (EDh)" has a sort-of protection system:
Quote
Many controllers use proprietary error correction code (ECC) schemes; thus, it is not
possible for Micron to protect unique ID data with factory-programmed ECC.
However, to ensure data integrity, Micron programs the noted NAND Flash devices with a 16-byte
unique ID, beginning at byte 0 of the page, then follows with 16 bytes of complement ID.
These 32 bytes of data are then repeated a total of 16 times, such that the last byte of the
last copy of complement unique ID resides at byte 511 in the page.
The user can simply  XOR the first copy of the unique ID and its complement. If the result is “1,” the unique ID is good.
In the unlikely event that the result is non-zero, the user can repeat the XOR operation on a subsequent copy of the unique ID data.


You'll need to know the ECC used in the system where you took the nand from.

Did you see this?
https://github.com/SySS-Research/nand-dump-tools
Title: Re: help calculate Micron NAND on die ECC
Post by: carver on September 11, 2021, 08:19:41 pm
sorry for the silence, I forgot to subscribe to the topic.

thanks for the link, I will try to search for the algorithm there.

but I wrote everything right, in my case, it is the internal ECC in the NAND Micron.
it does not depend on the OS in any way (

I use JTAG and, and simple loader (code from MPC8321 manual) to work with NAND.
I erase flash, read all 0xFF, write 0x800, and read 0x800 data + 0x40 ECC back.
so I wrote above, the bits indicate hardware ECC in NAND, and CPU like MPC8321  - haven't ECC.


on the Internet - there was an ECC Micron algorithm, but it gives me different values ((

Micron is a well-known manufacturer, Linux/Uboot mentions "on die ECC",
so I was hoping that someone might have already solved this ECC or would point out my mistake.

p,s, yea, 2048+64 = 512+512+512+512+4+4+4+4+4+4+4+4+8+8+8+8,
so I post only one 528 block, where 516 bytes  - data, 4 bytes - "not used", 8 bytes - ECC.
..oh, need fix my first post. 512->512+4(for data).
Title: Re: help calculate Micron NAND on die ECC
Post by: DavidAlfa on September 15, 2021, 08:30:03 pm
It's strange. I got at least 3 different datasheets with different data.
I guess due the AAD/ABD/AABWP/BABWP/etc variations.

The last datasheet shows what you say.
ECC is done by on-die hardware, so after enabling the ECC bit, it should be managed automatically when writing/reading data?
So, unless the data is damaged beyond what ECC can repair, you should be getting correct data?
I suspect you should only read or write to the first 2048 Bytes, leaving the rest for the ECC.
So writing 2048 bytes to a page should "refresh" the ECC data?
Title: Re: help calculate Micron NAND on die ECC
Post by: carver on September 15, 2021, 11:28:10 pm
yea. at my pdf 2C CA 90 D5 86 = Micron MT29F2G16ABAEA.

before I save forum and gogle space, and post only 512+16 bytes, here full 2112 bytes (2048 + 64 bytes)
Code: [Select]
00000000  65 72 72 75 70 74 73 00  64 69 73 61 62 6c 65 64  |errupts.disabled|
00000010  20 68 61 72 64 20 69 6e  74 65 72 72 75 70 74 73  | hard interrupts|
00000020  00 00 00 00 3c 34 3e 69  6e 69 74 63 61 6c 6c 20  |....<4>initcall |
00000030  61 74 20 30 78 25 70 00  3a 20 72 65 74 75 72 6e  |at 0x%p.: return|
00000040  65 64 20 77 69 74 68 20  25 73 0a 00 69 6e 69 74  |ed with %s..init|
00000050  2f 6d 61 69 6e 2e 63 00  2f 64 65 76 2f 63 6f 6e  |/main.c./dev/con|
00000060  73 6f 6c 65 00 00 00 00  3c 34 3e 57 61 72 6e 69  |sole....<4>Warni|
00000070  6e 67 3a 20 75 6e 61 62  6c 65 20 74 6f 20 6f 70  |ng: unable to op|
00000080  65 6e 20 61 6e 20 69 6e  69 74 69 61 6c 20 63 6f  |en an initial co|
00000090  6e 73 6f 6c 65 2e 0a 00  3c 34 3e 46 61 69 6c 65  |nsole...<4>Faile|
000000a0  64 20 74 6f 20 65 78 65  63 75 74 65 20 25 73 0a  |d to execute %s.|
000000b0  00 00 00 00 3c 34 3e 46  61 69 6c 65 64 20 74 6f  |....<4>Failed to|
000000c0  20 65 78 65 63 75 74 65  20 25 73 2e 20 20 41 74  | execute %s.  At|
000000d0  74 65 6d 70 74 69 6e 67  20 64 65 66 61 75 6c 74  |tempting default|
000000e0  73 2e 2e 2e 0a 00 00 00  2f 73 62 69 6e 2f 69 6e  |s......./sbin/in|
000000f0  69 74 00 00 2f 65 74 63  2f 69 6e 69 74 00 00 00  |it../etc/init...|
00000100  2f 62 69 6e 2f 69 6e 69  74 00 00 00 2f 62 69 6e  |/bin/init.../bin|
00000110  2f 73 68 00 4e 6f 20 69  6e 69 74 20 66 6f 75 6e  |/sh.No init foun|
00000120  64 2e 20 20 54 72 79 20  70 61 73 73 69 6e 67 20  |d.  Try passing |
00000130  69 6e 69 74 3d 20 6f 70  74 69 6f 6e 20 74 6f 20  |init= option to |
00000140  6b 65 72 6e 65 6c 2e 00  3c 34 3e 50 61 72 61 6d  |kernel..<4>Param|
00000150  65 74 65 72 20 25 73 20  69 73 20 6f 62 73 6f 6c  |eter %s is obsol|
00000160  65 74 65 2c 20 69 67 6e  6f 72 65 64 0a 00 00 00  |ete, ignored....|
00000170  3c 33 3e 55 6e 6b 6e 6f  77 6e 20 62 6f 6f 74 20  |<3>Unknown boot |
00000180  6f 70 74 69 6f 6e 20 60  25 73 27 3a 20 69 67 6e  |option `%s': ign|
00000190  6f 72 69 6e 67 0a 00 00  54 6f 6f 20 6d 61 6e 79  |oring...Too many|
000001a0  20 62 6f 6f 74 20 65 6e  76 20 76 61 72 73 20 61  | boot env vars a|
000001b0  74 20 60 25 73 27 00 00  54 6f 6f 20 6d 61 6e 79  |t `%s'..Too many|
000001c0  20 62 6f 6f 74 20 69 6e  69 74 20 76 61 72 73 20  | boot init vars |
000001d0  61 74 20 60 25 73 27 00  65 61 72 6c 79 20 6f 70  |at `%s'.early op|
000001e0  74 69 6f 6e 73 00 00 00  3c 34 3e 4d 61 6c 66 6f  |tions...<4>Malfo|
000001f0  72 6d 65 64 20 65 61 72  6c 79 20 6f 70 74 69 6f  |rmed early optio|
00000200  6e 20 27 25 73 27 0a 00  3c 35 3e 00 3c 35 3e 4b  |n '%s'..<5>.<5>K|
00000210  65 72 6e 65 6c 20 63 6f  6d 6d 61 6e 64 20 6c 69  |ernel command li|
00000220  6e 65 3a 20 25 73 0a 00  42 6f 6f 74 69 6e 67 20  |ne: %s..Booting |
00000230  6b 65 72 6e 65 6c 00 00  73 74 61 72 74 5f 6b 65  |kernel..start_ke|
00000240  72 6e 65 6c 28 29 3a 20  62 75 67 3a 20 69 6e 74  |rnel(): bug: int|
00000250  65 72 72 75 70 74 73 20  77 65 72 65 20 65 6e 61  |errupts were ena|
00000260  62 6c 65 64 20 65 61 72  6c 79 0a 00 3c 32 3e 69  |bled early..<2>i|
00000270  6e 69 74 72 64 20 6f 76  65 72 77 72 69 74 74 65  |nitrd overwritte|
00000280  6e 20 28 30 78 25 30 38  6c 78 20 3c 20 30 78 25  |n (0x%08lx < 0x%|
00000290  30 38 6c 78 29 20 2d 20  64 69 73 61 62 6c 69 6e  |08lx) - disablin|
000002a0  67 20 69 74 2e 0a 00 00  48 4f 4d 45 3d 2f 00 00  |g it....HOME=/..|
000002b0  54 45 52 4d 3d 6c 69 6e  75 78 00 00 69 6e 69 74  |TERM=linux..init|
000002c0  00 00 00 00 2f 64 65 76  2f 72 6f 6f 74 00 00 00  |..../dev/root...|
000002d0  3c 35 3e 56 46 53 3a 20  49 6e 73 65 72 74 20 25  |<5>VFS: Insert %|
000002e0  73 20 61 6e 64 20 70 72  65 73 73 20 45 4e 54 45  |s and press ENTE|
000002f0  52 0a 00 00 20 72 65 61  64 6f 6e 6c 79 00 00 00  |R... readonly...|
00000300  56 46 53 3a 20 4d 6f 75  6e 74 65 64 20 72 6f 6f  |VFS: Mounted roo|
00000310  74 20 28 25 73 20 66 69  6c 65 73 79 73 74 65 6d  |t (%s filesystem|
00000320  29 25 73 2e 0a 00 00 00  56 46 53 3a 20 43 61 6e  |)%s.....VFS: Can|
00000330  6e 6f 74 20 6f 70 65 6e  20 72 6f 6f 74 20 64 65  |not open root de|
00000340  76 69 63 65 20 22 25 73  22 20 6f 72 20 25 73 0a  |vice "%s" or %s.|
00000350  00 00 00 00 50 6c 65 61  73 65 20 61 70 70 65 6e  |....Please appen|
00000360  64 20 61 20 63 6f 72 72  65 63 74 20 22 72 6f 6f  |d a correct "roo|
00000370  74 3d 22 20 62 6f 6f 74  20 6f 70 74 69 6f 6e 0a  |t=" boot option.|
00000380  00 00 00 00 56 46 53 3a  20 55 6e 61 62 6c 65 20  |....VFS: Unable |
00000390  74 6f 20 6d 6f 75 6e 74  20 72 6f 6f 74 20 66 73  |to mount root fs|
000003a0  20 6f 6e 20 25 73 00 00  4e 6f 20 66 69 6c 65 73  | on %s..No files|
000003b0  79 73 74 65 6d 20 63 6f  75 6c 64 20 6d 6f 75 6e  |ystem could moun|
000003c0  74 20 72 6f 6f 74 2c 20  74 72 69 65 64 3a 20 00  |t root, tried: .|
000003d0  2f 73 79 73 2f 62 6c 6f  63 6b 2f 25 73 2f 64 65  |/sys/block/%s/de|
000003e0  76 00 00 00 25 75 3a 25  75 00 00 00 2f 73 79 73  |v...%u:%u.../sys|
000003f0  2f 62 6c 6f 63 6b 2f 25  73 2f 72 61 6e 67 65 00  |/block/%s/range.|
00000400  2f 73 79 73 00 00 00 00  73 79 73 66 73 00 00 00  |/sys....sysfs...|
00000410  2f 64 65 76 2f 00 00 00  6e 66 73 00 3c 36 3e 57  |/dev/...nfs.<6>W|
00000420  61 69 74 69 6e 67 20 25  64 73 65 63 20 62 65 66  |aiting %dsec bef|
00000430  6f 72 65 20 6d 6f 75 6e  74 69 6e 67 20 72 6f 6f  |ore mounting roo|
00000440  74 20 64 65 76 69 63 65  2e 2e 2e 0a 00 00 00 00  |t device........|
00000450  6d 74 64 00 3c 33 3e 25  73 0a 00 00 52 41 4d 44  |mtd.<3>%s...RAMD|
00000460  49 53 4b 3a 20 72 61 6e  20 6f 75 74 20 6f 66 20  |ISK: ran out of |
00000470  63 6f 6d 70 72 65 73 73  65 64 20 64 61 74 61 00  |compressed data.|
00000480  3c 33 3e 52 41 4d 44 49  53 4b 3a 20 69 6e 63 6f  |<3>RAMDISK: inco|
00000490  6d 70 6c 65 74 65 20 77  72 69 74 65 20 28 25 64  |mplete write (%d|
000004a0  20 21 3d 20 25 64 29 20  25 6c 64 0a 00 00 00 00  | != %d) %ld.....|
000004b0  69 6e 63 6f 6d 70 6c 65  74 65 20 6c 69 74 65 72  |incomplete liter|
000004c0  61 6c 20 74 72 65 65 00  69 6e 63 6f 6d 70 6c 65  |al tree.incomple|
000004d0  74 65 20 64 69 73 74 61  6e 63 65 20 74 72 65 65  |te distance tree|
000004e0  00 00 00 00 2f 64 65 76  2f 72 61 6d 00 00 00 00  |..../dev/ram....|
000004f0  3c 35 3e 52 41 4d 44 49  53 4b 3a 20 43 6f 6d 70  |<5>RAMDISK: Comp|
00000500  72 65 73 73 65 64 20 69  6d 61 67 65 20 66 6f 75  |ressed image fou|
00000510  6e 64 20 61 74 20 62 6c  6f 63 6b 20 25 64 0a 00  |nd at block %d..|
00000520  3c 35 3e 52 41 4d 44 49  53 4b 3a 20 72 6f 6d 66  |<5>RAMDISK: romf|
00000530  73 20 66 69 6c 65 73 79  73 74 65 6d 20 66 6f 75  |s filesystem fou|
00000540  6e 64 20 61 74 20 62 6c  6f 63 6b 20 25 64 0a 00  |nd at block %d..|
00000550  3c 35 3e 52 41 4d 44 49  53 4b 3a 20 63 72 61 6d  |<5>RAMDISK: cram|
00000560  66 73 20 66 69 6c 65 73  79 73 74 65 6d 20 66 6f  |fs filesystem fo|
00000570  75 6e 64 20 61 74 20 62  6c 6f 63 6b 20 25 64 0a  |und at block %d.|
00000580  00 00 00 00 3c 35 3e 52  41 4d 44 49 53 4b 3a 20  |....<5>RAMDISK: |
00000590  73 71 75 61 73 68 66 73  20 66 69 6c 65 73 79 73  |squashfs filesys|
000005a0  74 65 6d 20 66 6f 75 6e  64 20 61 74 20 62 6c 6f  |tem found at blo|
000005b0  63 6b 20 25 64 0a 00 00  3c 35 3e 52 41 4d 44 49  |ck %d...<5>RAMDI|
000005c0  53 4b 3a 20 4d 69 6e 69  78 20 66 69 6c 65 73 79  |SK: Minix filesy|
000005d0  73 74 65 6d 20 66 6f 75  6e 64 20 61 74 20 62 6c  |stem found at bl|
000005e0  6f 63 6b 20 25 64 0a 00  3c 35 3e 52 41 4d 44 49  |ock %d..<5>RAMDI|
000005f0  53 4b 3a 20 65 78 74 32  20 66 69 6c 65 73 79 73  |SK: ext2 filesys|
00000600  74 65 6d 20 66 6f 75 6e  64 20 61 74 20 62 6c 6f  |tem found at blo|
00000610  63 6b 20 25 64 0a 00 00  3c 35 3e 52 41 4d 44 49  |ck %d...<5>RAMDI|
00000620  53 4b 3a 20 43 6f 75 6c  64 6e 27 74 20 66 69 6e  |SK: Couldn't fin|
00000630  64 20 76 61 6c 69 64 20  52 41 4d 20 64 69 73 6b  |d valid RAM disk|
00000640  20 69 6d 61 67 65 20 73  74 61 72 74 69 6e 67 20  | image starting |
00000650  61 74 20 25 64 2e 0a 00  3c 33 3e 52 41 4d 44 49  |at %d...<3>RAMDI|
00000660  53 4b 3a 20 43 6f 75 6c  64 6e 27 74 20 61 6c 6c  |SK: Couldn't all|
00000670  6f 63 61 74 65 20 67 7a  69 70 20 62 75 66 66 65  |ocate gzip buffe|
00000680  72 0a 00 00 3c 33 3e 52  41 4d 44 49 53 4b 3a 20  |r...<3>RAMDISK: |
00000690  43 6f 75 6c 64 6e 27 74  20 61 6c 6c 6f 63 61 74  |Couldn't allocat|
000006a0  65 20 67 7a 69 70 20 77  69 6e 64 6f 77 0a 00 00  |e gzip window...|
000006b0  62 61 64 20 67 7a 69 70  20 6d 61 67 69 63 20 6e  |bad gzip magic n|
000006c0  75 6d 62 65 72 73 00 00  69 6e 74 65 72 6e 61 6c  |umbers..internal|
000006d0  20 65 72 72 6f 72 2c 20  69 6e 76 61 6c 69 64 20  | error, invalid |
000006e0  6d 65 74 68 6f 64 00 00  49 6e 70 75 74 20 69 73  |method..Input is|
000006f0  20 65 6e 63 72 79 70 74  65 64 00 00 4d 75 6c 74  | encrypted..Mult|
00000700  69 20 70 61 72 74 20 69  6e 70 75 74 00 00 00 00  |i part input....|
00000710  49 6e 70 75 74 20 68 61  73 20 69 6e 76 61 6c 69  |Input has invali|
00000720  64 20 66 6c 61 67 73 00  69 6e 76 61 6c 69 64 20  |d flags.invalid |
00000730  63 6f 6d 70 72 65 73 73  65 64 20 66 6f 72 6d 61  |compressed forma|
00000740  74 20 28 65 72 72 3d 31  29 00 00 00 69 6e 76 61  |t (err=1)...inva|
00000750  6c 69 64 20 63 6f 6d 70  72 65 73 73 65 64 20 66  |lid compressed f|
00000760  6f 72 6d 61 74 20 28 65  72 72 3d 32 29 00 00 00  |ormat (err=2)...|
00000770  6f 75 74 20 6f 66 20 6d  65 6d 6f 72 79 00 00 00  |out of memory...|
00000780  6f 75 74 20 6f 66 20 69  6e 70 75 74 20 64 61 74  |out of input dat|
00000790  61 00 00 00 69 6e 76 61  6c 69 64 20 63 6f 6d 70  |a...invalid comp|
000007a0  72 65 73 73 65 64 20 66  6f 72 6d 61 74 20 28 6f  |ressed format (o|
000007b0  74 68 65 72 29 00 00 00  63 72 63 20 65 72 72 6f  |ther)...crc erro|
000007c0  72 00 00 00 6c 65 6e 67  74 68 20 65 72 72 6f 72  |r...length error|
000007d0  00 00 00 00 52 41 4d 44  49 53 4b 3a 20 69 6d 61  |....RAMDISK: ima|
000007e0  67 65 20 74 6f 6f 20 62  69 67 21 20 28 25 64 4b  |ge too big! (%dK|
000007f0  69 42 2f 25 6c 64 4b 69  42 29 0a 00 2f 69 6e 69  |iB/%ldKiB)../ini|
00000800  ff ff ff ff ff ff ff ff  1b 47 01 e3 00 00 39 1e  |.........G....9.|
00000810  ff ff ff ff ff ff ff ff  fa 08 11 e9 00 30 23 06  |.............0#.|
00000820  ff ff ff ff ff ff ff ff  8f 6d ce 82 01 20 64 74  |.........m... dt|
00000830  ff ff ff ff ff ff ff ff  a3 be 30 85 01 e0 9e 8a  |..........0.....|


according pdf - internal ECC - its 8 bytes from 516 bytes (512 of data and 4 spare(in my case always 0xFFFFFFFF))

Earlier, on other devices, I came across the fact that after reading data and writing it to another device,
this new device didn't work. them due to uncorrected ECC data.

so, when I need write 0x800 to new flash, I need read 0x840 from old flash, and check ECC.

that's why I'm always check ECC in the read data. but i can't do this here ((