RE: [ecc] Reed Solomon decoder

[inada@singnet.com.sg]

Hi Duane,
Thanks for ur reply. Its interesting and exciting to know that 
implementation of RS 255,223 on XCV600 Fpga is a reality. I've done 
some research on the GF or the finite field multiplier, but there are some
parts which i'm not sure about. How does the multiplier replace the 
exponential/Binary LUT? Does it mean the multiplier includes the 
multiplications of any two alphas exponentials, mod, and XOR? And is 
there any docs or website that u recommend on the GF multiplier? Really 
appreciative if u can help... Thanks!!

Best Regards,
Yong Song. 

----- Original Message ----- 
From: "AJ Sahagun" <aj@a... > 
To: <ecc@o... > 
Date: Fri, 14 Mar 2003 09:11:54 +0800 
Subject: RE: [ecc] Reed Solomon decoder 

> 
> 
> 
> Hi Duane, 
> 
> Just curious, did your implementation not require any 
> exponential/binary 
> tables?  We did our own version of (255,223) RS in the past, and 
> though we 
> hardcoded our multipliers as you did, we still found the need for a 
> few 
> exponential/binary tables for division and exponentiation.  Did you 
> use an 
> implementation that required only GF addition and GF 
> multiplication, or 
> perhaps used a nifty technique for exponentiations and divisions?  
> It would 
> be very interesting to know. 
> 
> best regards, 
> aj 
> 
> 
> 
> -----Original Message----- 
> From: owner-ecc@o...  [mailto:owner-ecc@o... ]On 
> Behalf 
> Of Duane Clark 
> Sent: Thursday, March 13, 2003 1:14 AM 
> To: ecc@o...  
> Subject: Re: [ecc] Reed Solomon decoder 
> 
> 
> Of course, every multiplier is different, depending on the fixed 
> alpha 
> that the input is being multiplied by. I generate those with a C 
> code 
> algorithm that generates the output directly in VHDL format, which 
> I 
> then pipe into a package file. 
> 
> An additional big advantage of using a method such as this is that 
> it is 
> extremely fast. I did not bother to floorplan, and the decoder will 
> run 
> at 70MBytes per second. 
> 
> Because I had a bunch of spare block RAMs available, I implemented 
> some 
> of the multipliers in lookup tables. This freed up some LUTs to be 
> used 
> elsewhere. Again, this is hardcoded GF multipliers, and not 
> exponential/binary tables. A 256x16 block ROM can implement 16 
> multiplier bits. 
> 
> I used the same method of using C code to generate the contents of 
> the ROM. 
> 
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