Re: XAUI Related Issues
Hi Rich
Current 4 UI of skew is more than adequate for electrical skew.
My concern is skew granularity in presence of plugable module.
For completeness we need to breakdown the allocation.
We don't need to change the specifications, just divide the
skew across the link components. Since the specification
is rather relax, I propose the following skew allocation
for the two application of XAUI as listed below:
Transceiver (Con. for Module):
XAUI TX-----Con---Module---Fiber---Module---Con------XAUI RX
1ns 1nS 1ns 1ns
Passive Backplane(Con. for Backplane):
XAUI TX ----Con-----------------------------Con------XAUI RX
1ns 2 ns 1ns
Thanks,
Ali
Rich Taborek wrote:
>
> Ali,
>
> Here's my response to a Clause 48 related issue from your original note:
>
> "Kesling, Dawson W" wrote:
> >
> > Ali,
> >
> > Thank you for your inputs. I'm sorry I was too swamped to reply last week. I
> > was also hoping that some other participants would jump in and fill the gap
> > with their thoughts! My thoughts are embedded in your message below. I'm
> > still eager to hear what others think as well.
> >
> > -Dawson
> >
> > - We need to have better definition of how much skew you can
> > have lane to lane. Chapter 48 says you can have 1 UI allocated
> > to the PMA, but we need to allocated like 0.5 UI to the electrical
> > XAUI portion.
> > Dawson's comment: We should coordinate this with clause 48. The plenary is a
> > good time since clauses 47 and 48 will be sharing a room. I agree that 0.5UI
> > is reasonable for the interconnect. But since we haven't spec'ed the
> > interconnect so far, one thought is to spec the transmit lane-to-lane skew
> > and the the receive tolerance for lane-to-lane skew.
>
> In it's skew budget, Clause 48 supports 4 UI total skew for all PMA and
> PCB elements not including Rx deserialization and clock boundary
> transition. This includes the "electrical XAUI portion". I believe this
> value to be more than adequate. Actual XAUI deskew protocol supports
> greater than 2X the deskew budget. A specific comment proving beyond a
> reasonable doubt that the current skew budget is flawed is required at
> this point. This is the only way 75% of the Task Force would be inclined
> to make a change to the current skew budget.
>
> > Thanks,
> >
> > --
> > Ali Ghiasi
> > Broadcom Corp.
>
> --
>
> Best Regards,
> Rich
>
> -------------------------------------------------------
> Richard Taborek Sr. Phone: 408-845-6102
> Chief Technology Officer Cell: 408-832-3957
> nSerial Corporation Fax: 408-845-6114
> 2500-5 Augustine Dr. mailto:rtaborek@xxxxxxxxxxx
> Santa Clara, CA 95054 http://www.nSerial.com
--
Ali Ghiasi
Broadcom Corp.
--
Ali Ghiasi
Broadcom Corp.
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