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Re: /E/s and /T/s across the XGMII


Yes, this answers my question. In particular, I wanted
to get acknowledgment that the RX XGMII needs to
handle EOP error conditions which don't have a /T/.


pat_thaler@xxxxxxxxxxx wrote:
> Ben,
> As I stated at the meeting, one of the things that
> I believe should change in the state machine is the
> behavior of putting out Error continuously once an
> error has occurred.
> A better behavior is:
>   when an error occurs on the input, go to the E state
>    and send one E code block.
>   once the input doesn't contain errors, go to the state
>    that necessary to relay the input.
> Part of the reason I prefer this is that it is easier
> to diagnose and get to root cause on error situations
> when one has a more defined idea of what errors are
> being seen and in what kind of situations they are
> occurring. Sending continuous error isn't necessary
> and it hides information for diagnosis.
> Does this resolve the problem you see? I'm not quite
> sure I understand your exact concern. Note that the
> RS (and the XGXS) will need to tolerate the error
> case of a transition from Data to Error to Idle
> without a Terminate because an error can hit the
> terminate.
> Pat
> -----Original Message-----
> From: Ben Brown [mailto:bbrown@xxxxxxxx]
> Sent: Wednesday, October 04, 2000 7:32 AM
> To: 802.3ae
> Subject: /E/s and /T/s across the XGMII
> Bob Grow, Pat Thaler,
> Let's take a look at the following (XAUI less) case:
> The transmit RS chooses to drive the "Transmit Error
> Propagation" encoding across the XGMII during a packet,
> as shown in figure 46-4, page 107.
> The transmit PCS replaces that and all remaining words
> in the packet, including the word with the Terminate,
> with some number of 66-bit frames using the 0x1e Type
> Field and 8 Cx values of /E/. This is due to the state
> transition from the D state to the E state when
> TYPE(tx_tobe_coded) equals neither D nor T. When the
> RS/XGMII returns to sending Idles, the Transmit PCS
> will return to the Z state and send frames with the
> 0x1e Type Field and Cx values of /I/.
> The receive PCS follows the data coming from the
> transmitter and pretty much tracks states, transitioning
> from state D to state E when the transmitter does. When
> it does this, it stops sending Data across the XGMII
> and starts sending Receive Error. It does not do this
> in just one byte location as depicted in Figure 46-5,
> page 109. In fact, this errored packet won't even have
> a Terminate value across the XGMII.
> I don't think we can fix this by modifying the PCS,
> given the limited code space allowed by the 64B/66B
> encoding. I think we need to better describe the EOP
> over the XGMII in the case of errored packets.
> I haven't looked at XAUI/10GBASE-X PCS so I don't
> know if the problem also exists there.
> Thoughts?
> Ben
> --
> -----------------------------------------
> Benjamin Brown
> 2 Commerce Park West
> Suite 104
> Bedford NH 03110
> 603-641-9837 - Work
> 603-491-0296 - Cell
> 603-798-4115 - Home
> bbrown@xxxxxxxx
> -----------------------------------------

Benjamin Brown
2 Commerce Park West
Suite 104 
Bedford NH 03110
603-641-9837 - Work
603-491-0296 - Cell
603-798-4115 - Home