From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from majordomo by infradead.org with local (Exim 3.03 #1) id 13EKIJ-0000ev-00 for mtd-list@infradead.org; Tue, 18 Jul 2000 00:27:27 +0100 Received: from caja.ldhs.cetuc.puc-rio.br ([139.82.28.1]) by infradead.org with esmtp (Exim 3.03 #1) id 13EKIH-0000ep-00 for mtd@infradead.org; Tue, 18 Jul 2000 00:27:25 +0100 From: "Miguel Freitas" To: phiggins@transzap.com, mtd@infradead.org Date: Mon, 17 Jul 2000 20:26:30 GMT-3 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Subject: M-Sys Reed Solomon Reply-to: miguel@cetuc.puc-rio.br Message-ID: Sender: owner-mtd@infradead.org List-ID: Hi Patrick, I'm trying to understand the M-Systems Reed Solomon implementation used in DiskOnChip, maybe we could exchange some ideas... how is it going the code? I read your email when you went for vacation, more than a month ago. I have some comments on it, probably old ones for you, but let's try... 1) How do you know that these 4 x ten bit word encoded in that 6 interleaved bytes are actually the syndrom? It doesn't make sense for me... First, a syndrom should be zero for a correct block and second, they always transmit the ECC "parity" and never the syndrom itself. The syndrom is computed from the whole codeword (data+parity)...(apologize me if I'm stating the obvious). 2) Where did you get the information to convert the 6 interleaved bytes into 4 x ten bit word? The parallel 8 bit parity at the second byte is easy to see, but the 40 bits could be arranged in a different manner under 5 bytes. The M-Sys driver has a routine to do that conversion, but in another sequence (and without the parallel parity). 3) I guess you should have already figured out what is the primitive polynomial they use. Just in case, it's the classical x^10+x^3+1. This became clear with a little reverse engineering... I also tryed to match the hardware ECC data initializing the shift register encoder with symbols different than zero without success. Have you had more lucky in the last month? Regards, Miguel Freitas To unsubscribe, send "unsubscribe mtd" to majordomo@infradead.org