[Coco] Fwd: IP packets on my coco

[Dave Philipsen]

This explanation is pretty straightforward.  It involves basically 
bitshifting and XORing but it doesn't seem like it would be terribly 
intensive for the CPU.  Once you look at it and think about it a bit 
it's not as difficult as it might seem.

https://en.wikipedia.org/wiki/Cyclic_redundancy_check

Scroll down to the section entitled "Computation".


Another interesting thing I found is that you could write the CRC 
calculation in HDL and use an FPGA or similar device to do the 
calculation much faster than a 6809 could do it because it would be 
'hardwired' for the task and would run at a much higher clock speed.  
Just throwing out an idea....

Dave


On 6/7/2016 10:55 PM, William Astle wrote:
> On 16-06-07 09:39 PM, Brett Gordon wrote:
>> Nice!  I found that the fun part about CRC specs... they are usually
>> imcomplete.  They might tell you a polynomial.  but they seem to 
>> forget to
>> tell you all the minutiae.
>
> Technically, all you need is the polynomial to work out the CRC. 
> Unfortunately, if you don't already grok the math behind it, you're 
> left scratching your head, particularly how a 32 bit number can be a 
> polynomial. If you can find a good explanation of the CRC business, it 
> can be quite enlightening.
>