RE: clarification please

[Paul Koning <pkoning@equallogic.com>]

>>>>> "Vince" == A-Roseville,ex1  <CAVANNA> writes:

 Vince> Hi Paul, I used to agree with you on this, and that is what I
 Vince> had also communicated to Luben ( it was I who originally asked
 Vince> Julian to put in the iSCSI spec the same initial conditions
 Vince> for the CRC register as in ethernet), but ...  based on your
 Vince> description, the circuit you appear to have in mind is the
 Vince> circuit that performs simultaneous multiplication by x^32 and
 Vince> division by G(x). When you go through the same reasoning for
 Vince> the circuit that performs only division (and thus requires you
 Vince> to perform the pre-multiplication by x^32 externally) your two
 Vince> descriptions appear not to be equivalent; and that surprised
 Vince> me!

I suspect that you're right.

The circuit I'm referring to is the classic LFSR based CRC
implementation, described in Appendix C of the Ethernet spec (and seen
in software implementations in many places; I think I quoted
linux/drivers/net/ewrk3.c in the past).  That one indeed does the
multiplication along with the division.

I haven't seen circuits that do the division only, and I'm not sure I
could generate an example of what one might look like.

      paul