[bluetooth] few precisions

["Got' Gotferdomm" <gotferdomm@hotmail.com>]

Hi,

I got some VHDL code of the NOUR project about the CRC generator crc_gen.vhd 
(on http://www.geocities.com/SiliconValley/Pines/6639/ip/bt/) and i have 
some basic questions of understanding :

- First, what is the lfsr ? it seems to be a register for the flow control. 
And it doesn't appear in the register list and the bluetooth spec. doesn't 
really explain it.
it however seems to be used for the crc calculation.

- The data stream DataIn and DataOut don't seem to be 16 bits length data. 
>From your specifications, the crc is supposed to deal with 16 bits data, i 
don't understand. It means that data will arrive as a flow. But how CRC 
calculation is possible (because we have to send T(x)=x^16*M(x)-R(x), where 
R(x) is what remains in the euclid division between x^16*M(x) and G(x))

Why not sending directly T(x), calculated from DataIn[0..15] ?

- An other point is the following : the spec focus on the modification of 
SEQN and ARQN bits after CRC, for reception, but your CRC decoding doesn't 
seem to deal with these bits...
- Finally, i read the spec. but don't understand what is the initial value 
of CRC and why is it necessary ?

- I also have a global question about the Bluetooth norm : from the spec. 
SCO is the physical link for voice exchange and ACL is the physical link for 
data exchange : is it right ?

Thanks in advance for these basic questions...

Vincent,

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