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Allwinner A13
http://forum.hddguru.com/viewtopic.php?f=27&t=37650
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Author:  de Parcevaux [ November 5th, 2018, 18:22 ]
Post subject:  Allwinner A13

Hello,
Does anybody has BCH parameters for Allwinner A13 nand flash controller ?
It's for Reread a STorex Ezee tablet nand flash (H27UCG8T2ATR-BC)
I have found the XOR key. But I can't found the ECC parameters
Thanks

Author:  arvika [ November 7th, 2018, 1:37 ]
Post subject:  Re: Allwinner A13

Yes, here it is. Should be in DB, I sent it some time ago to developers. They do not add it?

Attachments:
A13_1078(ecc50b)_4.zip [512 Bytes]
Downloaded 7 times

Author:  malakai [ November 7th, 2018, 13:34 ]
Post subject:  Re: Allwinner A13

In unknown cases of ECC its worth to use codeword analysis tool. It's very easy and effective to use, Connect BCH element to physical image and as Payload you set assumed range of data area and eventually spare area if it exist, in Parity - range of ECC area (positions counted from 0). In this case it little more complicated because DA and Spare aren't in row. You can use offset to skip bytes between them (you have to shrink page size in codeword analyser settings as well). Polynomial is dec/hex representation of binary generation polynomial for parity bits e.g. 369d is binary 1 0111 0001 and polynomial for it is:

x^8 + x^6 + x^5+ x^4 + 1(x^0)

Degree is the value of highest power.

To choose correct degree for analyse add total length of payload and parity bytes for codeword ( in your case based on Michal's file it's 1028+50 = 1078 bytes and it's 8624 bits). 8624<16384 ( 2^14) so correct degree is 14.

You can also use predefined specific polynomial as well.
Result you receive will be in range 1-64 and it's ratio correctable codewords to tested codewrods (higher is better).

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